Citations
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This panel provides information on past usage of this interatomic potential (IP) powered by the OpenKIM Deep Citation framework. The word cloud indicates typical applications of the potential. The bar chart shows citations per year of this IP (bars are divided into articles that used the IP (green) and those that did not (blue)). The complete list of articles that cited this IP is provided below along with the Deep Citation determination on usage. See the Deep Citation documentation for more information.
78 Citations (56 used)
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USED (definite) R. Aguirre, S. Abdullah, X. W. Zhou, and D. Zubia, “Molecular Dynamics Calculations of Grain Boundary Mobility in CdTe,” Nanomaterials. 2019. link Times cited: 4 Abstract: Molecular dynamics (MD) simulations have been applied to stu… read moreAbstract: Molecular dynamics (MD) simulations have been applied to study mobilities of Σ3, Σ7 and Σ11 grain boundaries in CdTe. First, an existing MD approach to drive the motion of grain boundaries in face-centered-cubic and body-centered-cubic crystals was generalized for arbitrary crystals. MD simulations were next performed to calculate grain boundary velocities in CdTe crystals at different temperatures, driving forces, and grain boundary terminations. Here a grain boundary is said to be Te-terminated if its migration encounters sequentially Cd·Te−Cd·Te… planes, where “·” and “−” represent short and long spacing respectively. Likewise, a grain boundary is said to be Cd-terminated if its migration encounters sequentially Te·Cd−Te·Cd… planes. Grain boundary mobility laws, suitable for engineering time and length scales, were then obtained by fitting the MD results to Arrhenius equation. These studies indicated that the Σ3 grain boundary has significantly lower mobility than the Σ7 and Σ11 grain boundaries. The Σ7 Te-terminated grain boundary has lower mobility than the Σ7 Cd-terminated grain boundary, and that the Σ11 Cd-terminated grain boundary has lower mobility than the Σ11 Te-terminated grain boundary. read less USED (definite) X. W. Zhou and S. Foiles, “Uncertainty Quantification and Reduction of Molecular Dynamics Models.” 2017. link Times cited: 9 Abstract: Molecular dynamics (MD) is an important method underlying th… read moreAbstract: Molecular dynamics (MD) is an important method underlying the modern field of Computational Materials Science. Without requiring prior knowledge as inputs, MD simulations have been used to study a variety of material problems. However, results of molecular dynamics simulations are often associated with errors as compared with experimental observations. These errors come from a variety of sources, including inac- curacy of interatomic potentials, short length and time scales, idealized problem description and statistical uncertainties of MD simulations themselves. This chapter specifically devotes to the statistical uncertainties of MD simulations. In particular, methods to quantify and reduce such statistical uncertainties are demonstrated using a variety of exemplar cases, including calculations of finite temperature static properties such as lattice constants, cohesive energies, elastic constants, dislocation energies, ther- mal conductivities, surface segregation and calculations of kinetic properties such as diffusion parameters. We also demonstrate that when the statistical uncertainties are reduced to near zero, MD can be used to validate and improve widely used theories. read less USED (definite) J. J. Chavez, X. W. Zhou, S. Almeida, R. Aguirre, and D. Zubia, “Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation,” Journal of Materials Science Research. 2016. link Times cited: 11 Abstract: Molecular dynamics simulations were used to catalogue atomic… read moreAbstract: Molecular dynamics simulations were used to catalogue atomic scale structures of CdTe films grown on eight wurtzite (wz) and zinc-blende (zb) CdS surfaces. Polytypism, grain boundaries, dislocations and other film defects were detected. Dislocation lines were distributed in three distinct ways. For the growths on the wz {0001} and zb {111} surfaces, dislocations were found throughout the epilayers and formed a network at the interface. The dislocations within the films grown on the wz {1100}, wz {1120}, zb {110}, zb {010}, and zb {1/10 1 1/10} surfaces formed an interface network and also threaded from the interface towards the film’s surface. In contrast, the growth on the zb {112} surface only had dislocations localized to the interface. This film exhibited a different orientation from the substrate to reduce the lattice mismatch strain energies, and therefore, its misfit dislocation density. Our study indicates that the substrate orientation could be utilized to modify the morphology of dislocation networks in lattice mismatched multi-layered systems. read less USED (definite) S. Almeida, E. Ochoa, J. J. Chavez, X. W. Zhou, and D. Zubia, “Calculation of surface diffusivity and residence time by molecular dynamics with application to nanoscale selective-area growth,” Journal of Crystal Growth. 2015. link Times cited: 3 USED (definite) Z. Zhang et al., “Deformation twinning evolution from a single crystal in a face-centered-cubic ternary alloy,” Scientific Reports. 2015. link Times cited: 19 USED (high confidence) P. Brosseau, J. Geuchies, D. Jasrasaria, A. Houtepen, E. Rabani, and P. Kambhampati, “Ultrafast hole relaxation dynamics in quantum dots revealed by two-dimensional electronic spectroscopy,” Communications Physics. 2023. link Times cited: 5 USED (high confidence) D. Jasrasaria and E. Rabani, “Circumventing the phonon bottleneck by multiphonon-mediated hot exciton cooling at the nanoscale,” npj Computational Materials. 2023. link Times cited: 1 USED (high confidence) B. Hou, M. Thoss, U. Banin, and E. Rabani, “Incoherent nonadiabatic to coherent adiabatic transition of electron transfer in colloidal quantum dot molecules,” Nature Communications. 2022. link Times cited: 2 USED (high confidence) M. Wen, Y. Afshar, R. Elliott, and E. Tadmor, “KLIFF: A framework to develop physics-based and machine learning interatomic potentials,” Comput. Phys. Commun. 2021. link Times cited: 12 USED (high confidence) H. Huan, B. Fu, and X. Ye, “Tuning the thermal conductivity of wurtzite CdSe nanowires: effects of size, strain, torsion and temperature,” Philosophical Magazine. 2021. link Times cited: 1 Abstract: ABSTRACT The thermal transport of wurtzite CdSe nanowires (N… read moreAbstract: ABSTRACT The thermal transport of wurtzite CdSe nanowires (NWs) is studied by means of nonequilibrium molecular dynamics simulations. It is found that the length, diameter and strain can tune the thermal conductivity of CdSe NWs effectively, while the thermal conductivity exhibits insensitivity to torsion. The results indicate that the thermal conductivity of the CdSe NWs varies with the diameter approximately in the range of 13.8–17.7 W·m−1·K−1. The underlying mechanism is discussed by calculating the phonon power spectral density. The results show that the thermal transport is dominated by the centre atoms of NW, and high-frequency phonons contribute a lot to the thermal transport. Moreover, both tensile strain and compression strain can effectively suppress the thermal transport of CdSe NWs. The minimum thermal conductivity for the tensile strain and compression strain are 9.65 and 2.89 W·m−1·K−1, which are about 35% and 81% less than that of the unstrained structure. read less USED (high confidence) C. Yan et al., “Uncovering the Role of Hole Traps in Promoting Hole Transfer from Multiexcitonic Quantum Dots to Molecular Acceptors.,” ACS nano. 2020. link Times cited: 17 Abstract: Understanding electronic dynamics in multiexcitonic quantum … read moreAbstract: Understanding electronic dynamics in multiexcitonic quantum dots (QDs) is important for designing efficient systems useful in high power scenarios, such as solar concentrators and multielectron charge transfer. The multiple charge carriers within a QD can undergo undesired Auger recombination events, which rapidly annihilate carriers on picosecond time scales and generate heat from absorbed photons instead of useful work. Compared to the transfer of multiple electrons, the transfer of multiple holes has proven to be more difficult due to slower hole transfer rates. To probe the competition between Auger recombination and hole transfer in CdSe, CdS, and CdSe/CdS QDs of varying sizes, we synthesized a phenothiazine derivative with optimized functionalities for binding to QDs as a hole accepting ligand and for spectroscopic observation of hole transfer. Transient absorption spectroscopy was used to monitor the photoinduced absorption features from both trapped holes and oxidized ligands under excitation fluences where the averaged initial number of excitons in a QD ranged from ∼1 to 19. We observed fluence-dependent hole transfer kinetics that last around 100 ps longer than the predicted Auger recombination lifetimes, and the transfer of up to 3 holes per QD. Theoretical modeling of the kinetics suggests that binding of hole acceptors introduces trapping states significantly different from those in native QDs passivated with oleate ligands. Holes in these modified trap states have prolonged lifetimes, which promotes the hole transfer efficiency. These results highlight the beneficial role of hole-trapping states in devising hole transfer pathways in QD-based systems under multiexcitonic conditions. read less USED (high confidence) S. Goel et al., “Horizons of modern molecular dynamics simulation in digitalized solid freeform fabrication with advanced materials,” Materials Today Chemistry. 2020. link Times cited: 17 USED (high confidence) S. Abdullah, R. Aguirre, X. W. Zhou, and D. Zubia, “Growth Evolution of Polycrystalline CdTe/CdS with Atomic Scale Resolution via Molecular Dynamics,” 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC). 2019. link Times cited: 1 Abstract: A new method to study polycrystalline growth of CdTe layers … read moreAbstract: A new method to study polycrystalline growth of CdTe layers has been developed using Molecular Dynamics (MD). The results show the creation of polycrystalline CdTe/CdS structures that closely recreate the morphology of experimental polycrystalline growth. The growth shows the nucleation and coalescence of grains at early stages for CdS on amorphous CdS and CdTe on polycrystalline CdS. read less USED (high confidence) R. Aguirre et al., “Crystal Growth and Atom Diffusion in (Cu)ZnTe/CdTe via Molecular Dynamics,” IEEE Journal of Photovoltaics. 2018. link Times cited: 4 Abstract: Molecular dynamics (MD) simulations and experimental evapora… read moreAbstract: Molecular dynamics (MD) simulations and experimental evaporation were applied to study the growth of evaporated (Cu)ZnTe on mono- and polycrystalline CdTe. The simulated structures show polytypism and polycrystallinity, including texturing and grain boundaries, diffusion, and other phenomena in excellent qualitative agreement with experimental atomic probe tomography, transmission electron microscope, and secondary ion mass spectrometry. Results show formation of Cu clusters in nonstoichiometric growths even at early stages of deposition. Results also show significantly faster diffusion along defected regions (uncorrelated CdTe grain boundaries) as compared with more highly crystalline areas (high-symmetry grain boundaries and pristine regions). Activation energies and pre-exponential factors of Cu, Zn, and Te diffusion were determined using simulation. The MD model captures crystal growth phenomena with a high degree of fidelity. read less USED (high confidence) M. Yu and S. Kenny, “Modelling the deposition process on the CdTe/CdS interface,” Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms. 2017. link Times cited: 1 USED (high confidence) X. W. Zhou, J. J. Chavez, S. Almeida, and D. Zubia, “Understanding misfit strain releasing mechanisms via molecular dynamics simulations of CdTe growth on 112zinc-blende CdS,” Journal of Applied Physics. 2016. link Times cited: 11 Abstract: Molecular dynamics simulations have been used to analyse mic… read moreAbstract: Molecular dynamics simulations have been used to analyse microstructures of CdTe films grown on {112} surfaces of zinc-blende CdS. Interestingly, CdTe films grow in ⟨331⟩ orientations as opposed to ⟨112⟩ epitaxial orientations. At the CdTe-{331}/CdS-{112} interface, however, there exists an axis that is parallel to the ⟨110⟩ orientation of both CdS and CdTe. It is the direction orthogonal to this ⟨110⟩ that becomes different, being ⟨116⟩ for CdTe and ⟨111⟩ for CdS, respectively. Missing CdTe-{110} planes are found along the ⟨110⟩ axis, suggesting that the misfit strain is released by the conventional misfit dislocation mechanism along this axis. In the orthogonal axis, the misfit strain is found to be more effectively released by the new grain orientation mechanism. Our finding is supported by literature experimental observations of the change of growth direction when Cd0.96Zn0.04Te films are deposited on GaAs. Analyses of energetics clearly demonstrate the cause for the formation of the new orientation, and the insights gained from our studies can help understand the grain structures experimentally observed in lattice mismatched systems. read less USED (high confidence) S. Almeida, J. J. Chavez, X. W. Zhou, and D. Zubia, “Effect of substrate orientation on CdS homoepitaxy by molecular dynamics,” Journal of Crystal Growth. 2016. link Times cited: 4 USED (high confidence) F. van Swol, X. W. Zhou, S. R. Challa, and J. E. Martin, “Heterojunctions of model CdTe/CdSe mixtures,” Modelling and Simulation in Materials Science and Engineering. 2015. link Times cited: 0 Abstract: We report on the strain behavior of compound mixtures of mod… read moreAbstract: We report on the strain behavior of compound mixtures of model group II–VI semiconductors. We use the Stillinger–Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II–VI compounds such as CdTe and CdSe. We employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization to find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. From this we learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response. read less USED (high confidence) J. J. Chavez, X. W. Zhou, D. Ward, J. Cruz-Campa, and D. Zubia, “A molecular dynamics study on defect reduction in thin film Cd1−xZnxTe/CdS solar cells,” 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC). 2014. link Times cited: 1 Abstract: Recently developed molecular dynamics models have been appli… read moreAbstract: Recently developed molecular dynamics models have been applied to study the formation of defects during growth of ZnTe-on-CdS multilayers. Our studies indicated that misfit dislocations are formed during growth, and the dislocation density can be reduced if the ZnTe layer is grown in a nano island configuration as opposed to a continuous film. These results highlight the use of molecular dynamics methods in providing valuable defect formation mechanism insight and guiding experimental efforts to produce high efficiency Cd1-xZnxTe solar cells. read less USED (low confidence) C. Liu, W. Yip, S. To, B. Chen, and J. Xu, “Numerical Investigation on the Effects of Grain Size and Grinding Depth on Nano-Grinding of Cadmium Telluride Using Molecular Dynamics Simulation,” Nanomaterials. 2023. link Times cited: 0 Abstract: Cadmium telluride (CdTe) is known as an important semiconduc… read moreAbstract: Cadmium telluride (CdTe) is known as an important semiconductor material with favorable physical properties. However, as a soft-brittle material, the fabrication of high-quality surfaces on CdTe is quite challenging. To improve the fundamental understanding of the nanoscale deformation mechanisms of CdTe, in this paper, MD simulation was performed to explore the nano-grinding process of CdTe with consideration of the effects of grain size and grinding depth. The simulation results indicate that during nano-grinding, the dominant grinding mechanism could switch from elastic deformation to ploughing, and then cutting as the grinding depth increases. It was observed that the critical relative grain sharpness (RGS) for the transition from ploughing to cutting is greatly influenced by the grain size. Furthermore, as the grinding depth increases, the dominant subsurface damage mechanism could switch from surface friction into slip motion along the <110> directions. Meanwhile, as the grain size increases, less friction-induced damage is generated in the subsurface workpiece, and more dislocations are formed near the machined groove. Moreover, regardless of the grain size, it was observed that the generation of dislocation is more apparent as the dominant grinding mechanism becomes ploughing and cutting. read less USED (low confidence) K. Peng and E. Rabani, “Polaritonic Bottleneck in Colloidal Quantum Dots.,” Nano letters. 2023. link Times cited: 0 Abstract: Controlling the relaxation dynamics of excitons is key to im… read moreAbstract: Controlling the relaxation dynamics of excitons is key to improving the efficiencies of semiconductor-based applications. Confined semiconductor nanocrystals (NCs) offer additional handles to control the properties of excitons, for example, by changing their size or shape, resulting in a mismatch between excitonic gaps and phonon frequencies. This has led to the hypothesis of a significant slowing-down of exciton relaxation in strongly confined NCs, but in practice due to increasing exciton-phonon coupling and rapid multiphonon relaxation channels, the exciton relaxation depends only weakly on the size or shape. Here, we focus on elucidating the nonradiative relaxation of excitons in NCs placed in an optical cavity. We find that multiphonon emission of carrier governs the decay, resulting in a polariton-induced phonon bottleneck with relaxation time scales that are slower by orders of magnitude compared to the cavity-free case, while the photon fraction plays a secondary role. read less USED (low confidence) N. A. Pike and R. Pachter, “Fitting the charged-optimized many-body potential for the Al-O-Se-Zn system,” Computational Materials Science. 2023. link Times cited: 0 USED (low confidence) Y. Li, B. Gu, A. Diaz, S. Phillpot, D. McDowell, and Y. Chen, “Dislocation formation in the heteroepitaxial growth of PbSe/PbTe systems,” Acta Materialia. 2023. link Times cited: 2 USED (low confidence) A. Islam, M. S. Hasan, M. S. Islam, A. G. Bhuiyan, C. Stampfl, and J. Park, “Crystal orientation-dependent tensile mechanical behavior and deformation mechanisms of zinc-blende ZnSe nanowires,” Scientific Reports. 2023. link Times cited: 0 USED (low confidence) K. Lin, D. Jasrasaria, J. Yoo, M. Bawendi, H. Utzat, and E. Rabani, “Theory of Photoluminescence Spectral Line Shapes of Semiconductor Nanocrystals.,” The journal of physical chemistry letters. 2022. link Times cited: 3 Abstract: Single-molecule photoluminescence (PL) spectroscopy of semic… read moreAbstract: Single-molecule photoluminescence (PL) spectroscopy of semiconductor nanocrystals (NCs) reveals the nature of exciton-phonon interactions in NCs. Understanding the homogeneous spectral line shapes and their temperature dependence remains an open problem. Here, we develop an atomistic model to describe the PL spectrum of NCs, accounting for excitonic effects, phonon dispersion relations, and exciton-phonon couplings. We validate our model using single-NC measurements on CdSe/CdS NCs from T = 4 to 290 K, and we find that the slightly asymmetric main peak at low temperatures is comprised of a narrow zero-phonon line (ZPL) and acoustic phonon sidebands. Furthermore, we identify the specific phonon modes that give rise to the optical phonon sidebands. At temperatures above 200 K, the spectral line width shows a stronger dependence upon the temperature, which we demonstrate to be correlated with higher order exciton-phonon couplings. We also identify the line width dependence upon reorganization energy, NC core sizes, and shell thicknesses. read less USED (low confidence) C. Xu et al., “Anisotropic mechanical responses and plastic deformation mechanisms of cadmium telluride under indentations,” Applied Physics A. 2022. link Times cited: 2 USED (low confidence) Y. Li, Z. Zheng, A. Diaz, S. Phillpot, D. McDowell, and Y. Chen, “Resonant interaction between phonons and PbTe/PbSe (001) misfit dislocation networks,” Acta Materialia. 2022. link Times cited: 4 USED (low confidence) S. Abdullah, X. W. Zhou, R. Aguirre, and D. Zubia, “A computational approach to analyze grain structures of semiconductor compound films: Case study of CdTe/CdS multilayers,” MRS Advances. 2022. link Times cited: 0 Abstract: Grain structures impact the performance of semiconductor dev… read moreAbstract: Grain structures impact the performance of semiconductor devices. Molecular dynamics has been successfully applied to simulate the growth of semiconductor compounds, reproducing the experimentally observed complex zincblende and wurtzite grains. However, methodologies to characterize the simulated grain structures are still not mature, especially for semiconductors. This limits the usefulness of simulations in material optimization. In this work, the grain tracking algorithm originally developed by Panzarino et al. has been utilized to analyze the CdTe/CdS films obtained from molecular dynamics simulations. This work demonstrates that the parameters obtained from the polyhedral template matching algorithm in OVITO can be used to calculate the orientation of each grain. This provides a variety of useful information such as grain domains, grain orientations, plane indices, and sample texture. Moreover, dynamic analysis of microstructure evolution can be performed to understand grain growth mechanisms and kinetics. There are other useful features that are not included in the current tool such as identification and tracking of point defects (especially vacancies at grain boundaries). Nonetheless, the current approach is useful and our CdTe/CdS results provide input for further computational studies to relate grain structures to physical, chemical, mechanical, and electronic properties. read less USED (low confidence) A. Islam, M. S. Hasan, M. S. Islam, and J. Park, “Chirality, temperature, and vacancy effects on mechanical behavior of monolayer zinc-sulfide,” Computational Materials Science. 2021. link Times cited: 3 USED (low confidence) C. Xu, F.-ming Liu, C. Liu, P. Wang, and H. Liu, “Orientation Dependent Mechanical Responses and Plastic Deformation Mechanisms of ZnSe Nano Films under Nanoindentation,” Nanomaterials. 2021. link Times cited: 3 Abstract: Although ZnSe has been widely studied due to its attractive … read moreAbstract: Although ZnSe has been widely studied due to its attractive electronic and optoelectronic properties, limited data on its plastic deformations are available. Through molecular dynamics simulations, we have investigated the indentations on the (001), (110), and (111) planes of ZnSe nano films. Our results indicate that the elastic modulus, incipient plasticity, elastic recovery ratio, and the structural evolutions during the indenting process of ZnSe nano films show obvious anisotropy. To analyze the correlation of structural evolution and mechanical responses, the atomic displacement vectors, atomic arrangements, and the dislocations of the indented samples are analyzed. Our simulations revealed that the plastic deformations of the indented ZnSe nano films are dominated by the nucleation and propagation of 1/2<110> type dislocations, and the symmetrically distributed prismatic loops emitted during the indenting process are closely related with the mechanical properties. By studying the evolutions of microstructures, the formation process of the dislocations, as well as the formation mechanisms of the emitted prismatic loops under the indented crystalline planes are discussed. The results presented in this work not only provide an answer for the questions about indentation responses of ZnSe nano films, but also offer insight into its plastic deformation mechanisms. read less USED (low confidence) J. Chen and X. Zhang, “Thermal resistance and thermal rectification of silicon device with triangular pores: A molecular dynamics study,” Physics Letters A. 2021. link Times cited: 1 USED (low confidence) P. Hu, S. Wang, and Y. Zhuo, “Research on operation parameters and properties of flue gas on adsorption of As2O3 by γ-Al2O3: An experiment and simulation study,” Process Safety and Environmental Protection. 2021. link Times cited: 10 USED (low confidence) A. Islam, M. S. Islam, M. R. Islam, C. Stampfl, and J. Park, “Thermal transport in monolayer zinc-sulfide: effects of length, temperature and vacancy defects,” Nanotechnology. 2021. link Times cited: 5 Abstract: Of late, atomically thin two-dimensional zinc-sulfide (2D-Zn… read moreAbstract: Of late, atomically thin two-dimensional zinc-sulfide (2D-ZnS) shows great potential for advanced nanodevices and as a substitute to graphene and transition metal di-chalcogenides owing to its exceptional optical and electronic properties. However, the functional performance of nanodevices significantly depends on the effective heat management of the system. In this paper, we explored the thermal transport properties of 2D-ZnS through molecular dynamics simulations. The impact of length, temperature, and vacancy defects on the thermal properties of 2D-ZnS are systematically investigated. We found that the thermal conductivity (TC) rises monotonically with increasing sheet length, and the bulk TC of ∼30.67 W mK−1 is explored for an infinite length ZnS. Beyond room temperature (300 K), the TC differs from the usual 1/T rule and displays an abnormal, slowly declining behavior. The point vacancy (PV) shows the largest decrease in TC compared to the bi vacancy (BV) defects. We calculated phonon modes for various lengths, temperatures, and vacancies to elucidate the TC variation. Conversely, quantum corrections are used to avoid phonon modes’ icing effects on the TC at low temperatures. The obtained phonon density of states (PDOS) shows a softening and shrinking nature with increasing temperature, which is responsible for the anomaly in the TC at high temperatures. Owing to the increase of vacancy concentration, the PDOS peaks exhibit a decrease for both types of defects. Moreover, the variation of the specific heat capacity and entropy with BV and PV signify our findings of 2D-ZnS TC at diverse concentrations along with the different forms of vacancies. The results elucidated in this study will be a guide for efficient heat management of ZnS-based optoelectronic and nano-electronic devices. read less USED (low confidence) M. Rahman, E. Chowdhury, D. A. Redwan, and S. Hong, “Computational characterization of thermal and mechanical properties of single and bilayer germanene nanoribbon,” Computational Materials Science. 2021. link Times cited: 13 USED (low confidence) N. Hew, D. Spagnoli, and L. Faraone, “Dislocation core energies of the 0° perfect, 60° perfect, 30° partial, and 90° partial dislocations in CdTe, HgTe, and ZnTe: A molecular statics and elasticity theory analysis,” Materials today communications. 2021. link Times cited: 3 USED (low confidence) J. C. Ondry, J. Philbin, M. Lostica, E. Rabani, and A. Alivisatos, “Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices.,” ACS nano. 2020. link Times cited: 28 Abstract: By combining colloidal nanocrystal synthesis, self-assembly,… read moreAbstract: By combining colloidal nanocrystal synthesis, self-assembly, and solution phase epitaxial growth techniques, we developed a general method for preparing single dot thick atomically attached quantum dot (QD) superlattices with high-quality translational and crystallographic orientational order along with state-of-the-art uniformity in the attachment thickness. The procedure begins with colloidal synthesis of hexagonal prism shaped core/shell QDs (e.g., CdSe/CdS), followed by liquid subphase self-assembly and immobilization of superlattices on a substrate. Solution phase epitaxial growth of additional semiconductor material fills in the voids between the particles, resulting in a QD-in-matrix structure. The photoluminescence emission spectra of the QD-in-matrix structure retains characteristic 0D electronic confinement. Importantly, annealing of the resulting structures removes inhomogeneities in the QD-QD inorganic bridges, which our atomistic electronic structure calculations demonstrate would otherwise lead to Anderson-type localization. The piecewise nature of this procedure allows one to independently tune the size and material of the QD core, shell, QD-QD distance, and the matrix material. These four choices can be tuned to control many properties (degree of quantum confinement, quantum coupling, band alignments, etc.) depending on the specific applications. Finally, cation exchange reactions can be performed on the final QD-in-matrix, as demonstrated herein with a CdSe/CdS to HgSe/HgS conversion. read less USED (low confidence) D. P. Rai, A. Laref, M. Khuili, S. Al-Qaisi, T. Vu, and D. D. Vo, “Electronic, magnetic and optical properties of monolayer (ML) hexagonal ZnSe on vacancy defects at Zn sites from DFT-1/2 approach,” Vacuum. 2020. link Times cited: 13 USED (low confidence) J. Philbin and E. Rabani, “Auger Recombination Lifetime Scaling for Type-I and Quasi-Type-II Core/Shell Quantum Dots.,” The journal of physical chemistry letters. 2020. link Times cited: 22 Abstract: Having already achieved near-unity quantum yields, with prom… read moreAbstract: Having already achieved near-unity quantum yields, with promising properties for light-emitting diode, lasing, and charge separation applications, colloidal core/shell quantum dots have great technological potential. The shell thickness and band alignment of the shell and core materials are known to influence the efficiency of these devices. In many such applications, a key to improving the efficiency requires a deep understanding of multiexcitonic states. Herein, we elucidate the shell thickness and band alignment dependencies of the biexciton Auger recombination lifetime for quasi-type-II CdSe/CdS and type-I CdSe/ZnS core/shell quantum dots. We find that the biexciton Auger recombination lifetime increases with the total nanocrystal volume for quasi-type-II CdSe/CdS core/shell quantum dots and is independent of the shell thickness for type-I CdSe/ZnS core/shell quantum dots. In order to perform these calculations and compute Auger recombination lifetimes, we developed a low-scaling approach based on the stochastic resolution of identity. The numerical approach provided a framework to study the scaling of the biexciton Auger recombination lifetimes in terms of the shell thickness dependencies of the exciton radii, Coulomb couplings, and density of final states in quasi-type-II CdSe/CdS and type-I CdSe/ZnS core/shell quantum dots. read less USED (low confidence) B. Chettri et al., “Induced ferromagnetism in bilayer hexagonal Boron Nitride (h-BN) on vacancy defects at B and N sites,” arXiv: Materials Science. 2020. link Times cited: 16 USED (low confidence) R. Khadka, N. Baishnab, G. Opletal, and R. Sakidja, “Study of amorphous boron carbide (a-BxC) materials using Molecular Dynamics (MD) and Hybrid Reverse Monte Carlo (HRMC),” Journal of Non-crystalline Solids. 2020. link Times cited: 5 USED (low confidence) H. Abbas and J. Hahn, “Crystallization mechanism of liquid tellurium from classical molecular dynamics simulation,” Materials Chemistry and Physics. 2020. link Times cited: 6 USED (low confidence) X. W. Zhou, “Impact of Molecular Dynamics Simulations on Research and Development of Semiconductor Materials,” MRS Advances. 2019. link Times cited: 2 Abstract: Atomic scale defects critically limit performance of semicon… read moreAbstract: Atomic scale defects critically limit performance of semiconductor materials. To improve materials, defect effects and defect formation mechanisms must be understood. In this paper, we demonstrate multiple examples where molecular dynamics simulations have effectively addressed these issues that were not well addressed in prior experiments. In the first case, we report our recent progress on modelling graphene growth, where we found that defects in graphene are created around periphery of islands throughout graphene growth, not just in regions where graphene islands impinge as believed previously. In the second case, we report our recent progress on modelling TlBr, where we discovered that under an electric field, edge dislocations in TlBr migrate in both slip and climb directions. The climb motion ejects extensive vacancies that can cause the rapid aging of the material seen in experiments. In the third case, we discovered that the growth of InGaN films on (0001) surfaces suffers from a serious polymorphism problem that creates enormous amounts of defects. Growth on (1120) surfaces, on the other hand, results in single crystalline wurtzite films without any of these defects. In the fourth case, we first used simulations to derive dislocation energies that do not possess any noticeable statistical errors, and then used these error-free methods to discover possible misuse of misfit dislocation theory in past thin film studies. Finally, we highlight the significance of molecular dynamics simulations in reducing defects in the design space of nanostructures. read less USED (low confidence) J. C. Ondry et al., “Resilient Pathways to Atomic Attachment of Quantum Dot Dimers and Artificial Solids from Faceted CdSe Quantum Dot Building Blocks.,” ACS nano. 2019. link Times cited: 25 Abstract: The goal of this work is to identify favored pathways for pr… read moreAbstract: The goal of this work is to identify favored pathways for preparation of defect resilient attached wurtzite CdX (X = S, Se, Te) nanocrystals. We seek guidelines for oriented attachment of faceted nanocrystals that are most likely to yield pairs of nanocrystals with either few or no electronic defects, or electronic defects that are in and of themselves desirable and stable. Using a combination of in-situ high resolution transmission electron microscopy (HRTEM) and electronic structure calculations, we evaluate the relative merits of atomic attachment of wurtzite CdSe nanocrystals on the {11 ̅00} or {112 ̅0} family of facets. Pairwise attachment on either facet can lead to perfect interfaces, provided the nanocrystal facets are perfectly flat and the angles between the nanocrystals can adjust during the assembly. Considering defective attachment, we observe for {11 ̅00} facet attachment that only one type of edge dislocation forms, creating deep hole traps. For {112 ̅0} facet attachment, we observe that four distinct types of extended defects form, some of which lead to deep hole traps while others only to shallow hole traps. HRTEM movies of the dislocation dynamics show that dislocations at {11 ̅00} interfaces can be removed, albeit slowly. Whereas only some extended defects at {112 ̅0} interfaces could be removed, others were trapped at the interface. Based on these insights, we identify the most resilient pathways to atomic attachment of pairs of wurtzite CdX nanocrystals and consider how these insights can translate to creation of electronically useful materials from quantum dots with other crystal structures. read less USED (low confidence) C. Chen, P. Song, F. Meng, P. Ou, X. Liu, and J. Song, “Predictive modeling of misfit dislocation induced strain relaxation effect on self-rolling of strain-engineered nanomembranes,” Applied Physics Letters. 2018. link Times cited: 2 Abstract: Combining atomistic simulations and continuum modeling, the … read moreAbstract: Combining atomistic simulations and continuum modeling, the effects of misfit dislocations on strain relaxation and subsequently self-rolling of strain-engineered nanomembranes have been investigated. Two representative material systems including (GaN/In0.5Ga0.5N) of wurtzite lattice and II–VI materials (CdTe/CdTe0.5S0.5) of zinc-blend lattice were considered. The atomistic characteristics of dislocation and the resulting lattice distorting were first determined by generalized-stacking-fault energy profile and disregistry function obtained through Peierls-Nabarro model. Those properties were then used to calculate the accurate mismatch strain of those nanomembranes with the presence of dislocations, and as inputs into von-Karman shell theory to quantitatively evaluate the effects on self-rolling curvature and anisotropy. The theoretical results were further confirmed by atomistic simulations of different crystal geometries and dislocation configurations. Our results provide essential theoretical insights ... read less USED (low confidence) T. Majdi, S. Pal, A. Hafreager, S. Murad, R. Sahu, and I. Puri, “Altering thermal transport by strained-layer epitaxy,” Applied Physics Letters. 2018. link Times cited: 4 Abstract: Since strain changes the interatomic spacing of matter and a… read moreAbstract: Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain can modify the thermal conductivity k of a material. We show how the strain induced by heteroepitaxy is a passive mechanism to change k in a thin film. Molecular dynamics simulations of the deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain in the conductivity of a deposited film. ZnTe films grow strain-free on lattice-matched ZnTe substrates, but similar thin films grown on a lattice-mismatched CdTe substrate exhibit ∼6% biaxial in-plane tensile strain and ∼7% uniaxial out-of-plane compressive strain. In the T = 700 K–1100 K temperature range, the conductivities of strained ZnTe layers decrease to ∼60% of their unstrained values. The resulting understanding of dk/dT shows that strain engineering can be used to alter the performance of a thermal rectifier and also provides a framework for enhancing thermoelectric devices. read less USED (low confidence) B. Bonef et al., “High spatial resolution correlated investigation of Zn segregation to stacking faults in ZnTe/CdSe nanostructures,” Applied Physics Letters. 2018. link Times cited: 4 Abstract: The correlative use of atom probe tomography (APT) and energ… read moreAbstract: The correlative use of atom probe tomography (APT) and energy dispersive x-ray spectroscopy in scanning transmission electron microscopy (STEM) allows us to characterize the structure of ZnTe/CdSe superlattices at the nanometre scale. Both techniques reveal the segregation of zinc along [111] stacking faults in CdSe layers, which is interpreted as a manifestation of the Suzuki effect. Quantitative measurements reveal a zinc enrichment around 9 at. % correlated with a depletion of cadmium in the stacking faults. Raw concentration data were corrected so as to account for the limited spatial resolution of both STEM and APT techniques. A simple calculation reveals that the stacking faults are almost saturated in Zn atoms (∼66 at. % of Zn) at the expense of Cd that is depleted. read less USED (low confidence) X. Qian, X. Gu, and R. Yang, “Thermal conductivity modeling of hybrid organic-inorganic crystals and superlattices,” Nano Energy. 2017. link Times cited: 31 USED (low confidence) R. Aguirre, J. J. Chavez, X. W. Zhou, and D. Zubia, “High Fidelity Polycrystalline CdTe/CdS Heterostructures via Molecular Dynamics,” MRS Advances. 2017. link Times cited: 3 Abstract: Molecular dynamics simulations of polycrystalline growth of … read moreAbstract: Molecular dynamics simulations of polycrystalline growth of CdTe/CdS heterostructures have been performed. First, CdS was deposited on an amorphous CdS substrate, forming a polycrystalline film. Subsequently, CdTe was deposited on top of the polycrystalline CdS film. Cross-sectional images show grain formation at early stages of the CdS growth. During CdTe deposition, the CdS structure remains almost unchanged. Concurrently, CdTe grain boundary motion was detected after the first 24.4 nanoseconds of CdTe deposition. With the elapse of time, this grain boundary pins along the CdS/CdTe interface, leaving only a small region of epitaxial growth. CdTe grains are larger than CdS grains in agreement with experimental observations in the literature. Crystal phase analysis shows that zinc blende structure dominates over the wurtzite structure inside both CdS and CdTe grains. Composition analysis shows Te and S diffusion to the CdS and CdTe films, respectively. These simulated results may stimulate new ideas for studying and improving CdTe solar cell efficiency. read less USED (low confidence) Q. Xiang et al., “Deformation mechanisms and twin boundary effects in cadmium telluride under nanoindentation,” Ceramics International. 2017. link Times cited: 4 USED (low confidence) X. W. Zhou, J. J. Chavez, and D. Zubia, “Molecular Dynamics Analysis of Nanostructures.” 2016. link Times cited: 0 USED (low confidence) A. Kelley, “Comparison of three empirical force fields for phonon calculations in CdSe quantum dots.,” The Journal of chemical physics. 2016. link Times cited: 11 Abstract: Three empirical interatomic force fields are parametrized us… read moreAbstract: Three empirical interatomic force fields are parametrized using structural, elastic, and phonon dispersion data for bulk CdSe and their predictions are then compared for the structures and phonons of CdSe quantum dots having average diameters of ˜2.8 and ˜5.2 nm (˜410 and ˜2630 atoms, respectively). The three force fields include one that contains only two-body interactions (Lennard-Jones plus Coulomb), a Tersoff-type force field that contains both two-body and three-body interactions but no Coulombic terms, and a Stillinger-Weber type force field that contains Coulombic interactions plus two-body and three-body terms. While all three force fields predict nearly identical peak frequencies for the strongly Raman-active "longitudinal optical" phonon in the quantum dots, the predictions for the width of the Raman peak, the peak frequency and width of the infrared absorption peak, and the degree of disorder in the structure are very different. The three force fields also give very different predictions for the variation in phonon frequency with radial position (core versus surface). The Stillinger-Weber plus Coulomb type force field gives the best overall agreement with available experimental data. read less USED (low confidence) X. W. Zhou, M. E. Foster, R. Jones, P. Yang, H. Fan, and F. Doty, “A modified Stillinger-Weber potential for TlBr and its polymorphic extension,” Journal of Materials Science Research. 2015. link Times cited: 6 Abstract: TlBr is promising for g- and x- radiation detection, but suf… read moreAbstract: TlBr is promising for g- and x- radiation detection, but suffers from rapid performance degradation under the operating external electric fields. To enable molecular dynamics (MD) studies of this degradation, we have developed a Stillinger-Weber type of TlBr interatomic potential. During this process, we have also addressed two problems of wider interests. First, the conventional Stillinger-Weber potential format is only applicable for tetrahedral structures (e.g., diamond-cubic, zinc-blende, or wurtzite). Here we have modified the analytical functions of the Stillinger-Weber potential so that it can now be used for other crystal structures. Second, past modifications of interatomic potentials cannot always be applied by a broad community because any new analytical functions of the potential would require corresponding changes in the molecular dynamics codes. Here we have developed a polymorphic potential model that simultaneously incorporates Stillinger-Weber, Tersoff, embedded-atom method, and any variations (i.e., modified functions) of these potentials. We have implemented this polymorphic model in MD code LAMMPS, and demonstrated that our TlBr potential enables stable MD simulations under external electric fields. read less USED (low confidence) Y. Wu, R.-B. Li, J. Xiao, and Y. Jiang, “Crystallization in Supercooled BCC-Vanadium, HCP-Zinc and FCC-Aluminum.” 2015. link Times cited: 0 USED (low confidence) J. Farrell and D. Wales, “Clusters of coarse-grained water molecules.,” The journal of physical chemistry. A. 2014. link Times cited: 4 Abstract: Global optimization for molecular clusters can be significan… read moreAbstract: Global optimization for molecular clusters can be significantly more difficult than for atomic clusters because of the coupling between orientational and translational degrees of freedom. A coarse-grained representation of the potential can reduce the complexity of this problem, while retaining the essential features of the intermolecular interactions. In this study, we use a basin-hopping algorithm to locate putative global minima for clusters of coarse-grained water molecules modeled using a monatomic water potential for cluster sizes 3 ≤ N ≤ 55. We characterize these structures and identify structural trends using ideas from graph theory. The agreement with atomistic results and experiment is rather patchy, which we attribute to the tetrahedral bias in the three-body potential that results in too few nearest neighbor contacts and premature emergence of bulk-like structure. In spite of this issue, the results offer further useful insight into the relationship between the structure of clusters and bulk phases, and the mathematical form of a widely used model potential. read less USED (low confidence) D. Nath and R. Das, “Experimental (XRD) and theoretical (DFT) analysis for understanding the influence of SHI irradiation on the stacking fault energy in CdSe nanocrystals,” Journal of Alloys and Compounds. 2021. link Times cited: 4 USED (low confidence) R. Jones, C. Weinberger, S. Coleman, and G. Tucker, “Introduction to Atomistic Simulation Methods.” 2016. link Times cited: 1 NOT USED (high confidence) D. Jasrasaria and E. Rabani, “Interplay of Surface and Interior Modes in Exciton-Phonon Coupling at the Nanoscale.,” Nano letters. 2021. link Times cited: 6 Abstract: Exciton-phonon coupling (EXPC) plays a key role in the optoe… read moreAbstract: Exciton-phonon coupling (EXPC) plays a key role in the optoelectronic properties of semiconductor nanocrystals (NCs), but a microscopic picture of EXPC is still lacking, particularly regarding the magnitude and scaling with NC size, the dependence on phonon frequency, and the role of the NC surface. The computational complexity associated with accurately describing excitons and phonons has limited previous theoretical studies of EXPC to small NCs, noninteracting electron-hole models, and/or a small number of phonon modes. Here, we develop an atomistic approach for describing EXPC in NCs of experimentally relevant sizes. We validate our approach by calculating the reorganization energies, a measure of EXPC, for CdSe and CdSe-CdS core-shell NCs, finding good agreement with experimental measurements. We demonstrate that exciton formation distorts the NC lattice primarily along the coordinates of low-frequency acoustic modes. Modes at the NC surface play a significant role in smaller NCs while interior modes dominate for larger systems. read less NOT USED (high confidence) E. Chowdhury, M. Rahman, R. Jayan, and M. M. Islam, “Atomistic investigation on the mechanical properties and failure behavior of zinc-blende cadmium selenide (CdSe) nanowire,” Computational Materials Science. 2021. link Times cited: 2 NOT USED (high confidence) C. Chen et al., “Vacancy-assisted core transformation and mobility modulation of a-type edge dislocations in wurtzite GaN,” Journal of Physics D: Applied Physics. 2019. link Times cited: 3 Abstract: In this study, core structure dependent dislocation dynamics… read moreAbstract: In this study, core structure dependent dislocation dynamics of a-type edge dislocation in three slip systems (basal, prismatic and pyramidal) of wurtzite GaN have been investigated using classical molecular dynamics simulations. All potential a-type edge dislocation cores in the shuffle and glide planes of the three slip systems have been identified, and the corresponding dislocation dynamics were examined. Our calculations reveal that for all of the three slip systems, all of the shuffle cores are planar glissile and mobile, while being non-planar sessile and immobile for all of the glide cores. We further show that vacancy can be used to activate the motion of glide cores via core transition from glide to shuffle, which is also valid for AlN and InN. The critical shear stresses for the motion of glide cores are also determined at various vacancy concentrations. Our study clarifies core structure dependent dislocation dynamics characteristics and provides ways in tuning dislocation motions in wurtzite crystals. read less NOT USED (high confidence) H. Hieu et al., “Structural and Thermomechanical Properties of Zincblende-Type ZnX (X = S, Se, Te),” Journal of Electronic Materials. 2019. link Times cited: 1 NOT USED (high confidence) M. Vohra, A. Nobakht, S. Shin, and S. Mahadevan, “Uncertainty quantification in non-equilibrium molecular dynamics simulations of thermal transport,” International Journal of Heat and Mass Transfer. 2018. link Times cited: 14 NOT USED (high confidence) M. Wen, S. Shirodkar, P. Plecháč, E. Kaxiras, R. Elliott, and E. Tadmor, “A force-matching Stillinger-Weber potential for MoS2: Parameterization and Fisher information theory based sensitivity analysis,” Journal of Applied Physics. 2017. link Times cited: 25 Abstract: Two-dimensional molybdenum disulfide (MoS2) is a promising m… read moreAbstract: Two-dimensional molybdenum disulfide (MoS2) is a promising material for the next generation of switchable transistors and photodetectors. In order to perform large-scale molecular simulations of the mechanical and thermal behavior of MoS2-based devices, an accurate interatomic potential is required. To this end, we have developed a Stillinger-Weber potential for monolayer MoS2. The potential parameters are optimized to reproduce the geometry (bond lengths and bond angles) of MoS2 in its equilibrium state and to match as closely as possible the forces acting on the atoms along a dynamical trajectory obtained from ab initio molecular dynamics. Verification calculations indicate that the new potential accurately predicts important material properties including the strain dependence of the cohesive energy, the elastic constants, and the linear thermal expansion coefficient. The uncertainty in the potential parameters is determined using a Fisher information theory analysis. It is found that the parameters are... read less NOT USED (high confidence) X. W. Zhou, R. Jones, and K. Chu, “Polymorphic improvement of Stillinger-Weber potential for InGaN,” Journal of Applied Physics. 2017. link Times cited: 4 Abstract: A Stillinger-Weber potential is computationally very efficie… read moreAbstract: A Stillinger-Weber potential is computationally very efficient for molecular dynamics simulations. Despite its simple mathematical form, the Stillinger-Weber potential can be easily parameterized to ensure that crystal structures with tetrahedral bond angles (e.g., diamond-cubic, zinc-blende, and wurtzite) are stable and have the lowest energy. As a result, the Stillinger-Weber potential has been widely used to study a variety of semiconductor elements and alloys. When studying an A-B binary system, however, the Stillinger-Weber potential is associated with two major drawbacks. First, it significantly overestimates the elastic constants of elements A and B, limiting its use for systems involving both compounds and elements (e.g., an A/AB multilayer). Second, it prescribes equal energy for zinc-blende and wurtzite crystals, limiting its use for compounds with large stacking fault energies. Here, we utilize the polymorphic potential style recently implemented in LAMMPS to develop a modified Stillinger-Weber potential for InGaN that overcomes these two problems.A Stillinger-Weber potential is computationally very efficient for molecular dynamics simulations. Despite its simple mathematical form, the Stillinger-Weber potential can be easily parameterized to ensure that crystal structures with tetrahedral bond angles (e.g., diamond-cubic, zinc-blende, and wurtzite) are stable and have the lowest energy. As a result, the Stillinger-Weber potential has been widely used to study a variety of semiconductor elements and alloys. When studying an A-B binary system, however, the Stillinger-Weber potential is associated with two major drawbacks. First, it significantly overestimates the elastic constants of elements A and B, limiting its use for systems involving both compounds and elements (e.g., an A/AB multilayer). Second, it prescribes equal energy for zinc-blende and wurtzite crystals, limiting its use for compounds with large stacking fault energies. Here, we utilize the polymorphic potential style recently implemented in LAMMPS to develop a modified Stillinger-Weber... read less NOT USED (high confidence) A. Takahashi, A. Seko, and I. Tanaka, “Linearized machine-learning interatomic potentials for non-magnetic elemental metals: Limitation of pairwise descriptors and trend of predictive power.,” The Journal of chemical physics. 2017. link Times cited: 20 Abstract: Machine-learning interatomic potential (MLIP) has been of gr… read moreAbstract: Machine-learning interatomic potential (MLIP) has been of growing interest as a useful method to describe the energetics of systems of interest. In the present study, we examine the accuracy of linearized pairwise MLIPs and angular-dependent MLIPs for 31 elemental metals. Using all of the optimal MLIPs for 31 elemental metals, we show the robustness of the linearized frameworks, the general trend of the predictive power of MLIPs, and the limitation of pairwise MLIPs. As a result, we obtain accurate MLIPs for all 31 elements using the same linearized framework. This indicates that the use of numerous descriptors is the most important practical feature for constructing MLIPs with high accuracy. An accurate MLIP can be constructed using only pairwise descriptors for most non-transition metals, whereas it is very important to consider angular-dependent descriptors when expressing interatomic interactions of transition metals. read less NOT USED (high confidence) X. W. Zhou and R. Jones, “A Stillinger-Weber Potential for InGaN,” Journal of Materials Science Research. 2017. link Times cited: 9 Abstract: Reducing defects in InGaN films deposited on GaN substrates … read moreAbstract: Reducing defects in InGaN films deposited on GaN substrates has been critical to fill the “green” gap for solid-state lighting applications. To enable researchers to use molecular dynamics vapor deposition simulations to explores ways to reduce defects in InGaN films, we have developed and characterized a Stillinger-Weber potential for InGaN. We show that this potential reproduces the experimental atomic volume, cohesive energy, and bulk modulus of the equilibrium wurtzite / zinc-blende phases of both InN and GaN. Most importantly, the potential captures the stability of the correct phase of InGaN compounds against a variety of other elemental, alloy, and compound configurations. This is validated by the potential’s ability to predict crystalline growth of stoichiometric wurtzite and zinc-blende InxGa1-xN compounds during vapor deposition simulations where adatoms are randomly injected to the growth surface. read less NOT USED (high confidence) X. W. Zhou, R. Jones, and J. Gruber, “Molecular dynamics simulations of substitutional diffusion,” Computational Materials Science. 2017. link Times cited: 23 NOT USED (high confidence) E. Voyiatzis and M. Böhm, “Atomic and global mechanical properties of systems described by the Stillinger–Weber potential,” Journal of Physics: Condensed Matter. 2016. link Times cited: 0 Abstract: Analytical expressions for the stress and elasticity tensors… read moreAbstract: Analytical expressions for the stress and elasticity tensors of materials, in which the interactions are described by the Stillinger–Weber potential, are derived in the context of the stress fluctuation formalism. The derived formulas can be used both in Monte Carlo and molecular dynamics simulations. As an example of possible applications, they are employed to calculate the influence of the temperature and system size on the mechanical properties of crystalline cubic boron nitride. The system has been studied by molecular dynamics simulations. The computed mechanical properties are in good agreement with available experimental data and first principle calculations. In the studied crystalline cubic boron nitride system, the employed formalism is of higher accuracy than the ‘small-strain’ non-equilibrium method. The dominant contributions to the elastic constants stem from the Born and stress fluctuation terms. An increase in the system size reduces the statistical uncertainties in the computation of the mechanical properties. A rise of the temperature leads to a slight increase in the observed uncertainties. The derived expressions for the stress and elasticity tensors are further decomposed into sums of atomic level stress and atomic level elasticity tensors. The developed factorization enables us (i) to quantify the contribution of the various chemical groups, in the case under consideration of the different atoms, to the observed mechanical properties and (ii) to determine the elastic constants with reduced computational uncertainties. The reason is that the exact values of some terms of the proposed factorization can be determined theoretically beforehand. Thus, they can be substituted in the derived formulas leading to an enhanced convergence. read less NOT USED (high confidence) X. W. Zhou et al., “An atomistically validated continuum model for strain relaxation and misfit dislocation formation,” Journal of The Mechanics and Physics of Solids. 2016. link Times cited: 21 NOT USED (high confidence) S. Schreyeck et al., “Kinetic limitation of chemical ordering in Bi2Te3−xSex layers grown by molecular beam epitaxy,” Journal of Physics: Condensed Matter. 2016. link Times cited: 4 Abstract: We study the chemical ordering in Bi2Te3−xSex grown by molec… read moreAbstract: We study the chemical ordering in Bi2Te3−xSex grown by molecular beam epitaxy on Si substrates. We produce films in the full composition range from x = 0 to 3, and determine their material properties using energy dispersive x-ray spectroscopy, x-ray diffraction and Raman spectroscopy. By fitting the parameters of a kinetic growth model to these results, we obtain a consistent description of growth at a microscopic level. Our main finding is that despite the incorporation of Se in the central layer being much more probable than that of Te, the formation of a fully ordered Te–Bi–Se–Bi–Te layer is prevented by kinetic of the growth process. Indeed, the Se concentration in the central layer of Bi2Te2Se1 reaches a maximum of only ≈75% even under ideal growth conditions. A second finding of our work is that the intensity ratio of the 0 0 12 and 0 0 6 x-ray reflections serves as an experimentally accessible quantitative measure of the degree of ordering in these films. read less NOT USED (high confidence) Z. Fan, “Molecular Simulations of Nanoscale Transformations in Ionic Semiconductor Nanocrystals.” 2016. link Times cited: 0 Abstract: The aim of the study described in this thesis is to obtain a… read moreAbstract: The aim of the study described in this thesis is to obtain a profound understanding of transformations in NCs at the atomic level, by performing molecular simulations for such transformations, and by comparing the simulation results with available experimental high resolution transmission electron microscopy (HRTEM) data to validate the simulations and to reveal underlying physical mechanisms. These transformations include structural and morphological transitions and cation exchange processes in ionic nanocrystals (II-VI and IV-VI semiconductors). The main simulation method used is classical Molecular Dynamics (MD) simulation. First principles density functional theory (DFT) calculations were used to develop empirical force fields that are able to accurately reproduce phase transitions. Using these newly developed force fields, large scaled classical MD simulations were carried out and linked to HRTEM experiments. The partially charged rigid ion model (PCRIM) was chosen for the force fields. This PCRIM approach has a simple functional form with a few number of parameters and has a clear physical meaning for ionic crystals. To simulate cation exchange in colloidal NC systems at the NC/solution interface, we used a combination of all-atom force fields and a coarse-grained model. In Chapter 2, an ab-initio based force field for ZnO is developed within the framework of the PCRIM approach. The values of the partial charges were determined by Bader charge analysis of DFT calculations on various ZnO phases. Beside Coulombic interactions, only short-ranged pairwise interatomic interactions were included. An initial guess of the parameters of the short-ranged pair potentials were first obtained by the lattice inversion method. The parameters were further adjusted by an ab-initio potential surface fitting procedure. The new ZnO force field has a very simple functional form is able to accurately reproduce several important physical properties of ZnO materials. These physical properties include the lattice parameters and phase stability of several ZnO polymorphs, as well as the elastic constants, bulk moduli, phonon dispersion, and melting points of wurtzite ZnO. The transition pressure of the wurtzite-to-rocksalt transition calculated with the force field equals 12.3 GPa, in agreement with experimental measurements and DFT calculations. A wurtzite-to-honeycomb phase transition is predicted at an uniaxial pressure of 8.8 GPa. We found a rational and effective way to derive force fields with simple functional forms for accurate simulations of phase transitions in ionic crystals. In Chapter 3, we developed a transferable force field for CdS-CdSe-PbSPbSe solid systems. The selection of the force field and the fitting procedure are similar to that of the ZnO force field in Chapter 2. The challenges when developing this force field were to maintain the transferability of this force field for four materials (CdS, CdSe, PbS, and PbSe) and to describe their mixed phases. This was solved by assuming that different cations/anions have the same values of the partial charges, and that shortranged interatomic interactions between two cations/anions are the same in different materials. For the mixed phases, DFT calculations of the mixed phases were included in both the training and validation sets. This work is the first step for further simulation studies of these II-VI and IV-VI semiconductor NCs and heteronanocrystals (HNCs). In Chapter 4, a thermally induced morphological and structural transition of CdSe NCs was investigated using MD simulations. In MD simulations, a CdSe nanosphere with the ZB structure transforms into a tetrapodlike morphology at 800 K. In a CdSe tetrapod, four WZ legs attach to the {111} facets of a tetrahedral ZB core. This transformation is achieved by a layer-by-layer slip of the ZB-{111} bilayer. Simulations show that the slips are mediated by the formation of Cd vacancies on the surface of the NCs to overcome the potentially large energy barriers associated with slip. The morphology of the annealed NCs is found to be temperature and size-dependent. An octapod-like morphology is found in NCs with a relatively large NC size and in a certain range of the heating temperature. Surprisingly, nanoscale transformations of CdSe NCs have been directly observed in HRTEM in situ heating experiments. Our findings provide a simple method to modify the morphology of ionic NCs and can potentially be used in the synthesis of branched NCs. The cation exchange process of PbSe/CdSe HNCs has been investigated by HRTEM in situ heating experiments in combination with MD simulations and DFT calculations in Chapter 5. In the HRTEM experiments, we bserved that Cd atoms in PbSe/CdSe nanodumbbells (CdSe rods with one or two PbSe tip(s)) are replaced by Pb atoms. The exchange rate depends on the heating temperature and the amount of Pb atoms present in the system. Sometimes, fully converted PbSe nanodumbells can be observed. MD simulations were performed to investigate the mechanism of this cation exchange process. It was found that the the CdSe domains near the PbSe/CdSe interfaces have significant structural disorder. These findings are in line with the experimental observation that the exchange process proceeds in a layer-by-layer fashion along the WZ- direction. We concluded that cation exchange in PbSe/CdSe HNCs is mediated by the local structural disorder which enables the formation of vacancies and accelerated the motion of cations. In Chapter 6, a coarse-grained psuedoligand model was introduced to simulate cation exchange in PbS colloidal NCs taking into account the cation-solvent interactions. Modelling colloidal NC systems including interactions with the solvent has long been a challenge due to the large system size and long time scales. Here, we incorporated the effects of ligands and solvents into negatively charged large spherical coarse-grained psuedoligands. MD simulations combining coarse-grained and all-atom models can successfully reproduce the cation exchange process in PbS colloidal NCs. Simulations show that the exchange rate and system equilibrium can be controlled by the temperature and by changing ligands. The exchange process is directly related to vacancy formation and the high mobility of Cd ions at the PbS/CdS interface. Our simulations also predict that high-pressure conditions will be beneficial for achieving fast exchange at elevated temperatures. Our coarse-grained model can be easily extended to other systems for the computational investigation of transformations in nanostructures. read less NOT USED (high confidence) F. van Swol, X. W. Zhou, S. R. Challa, and J. E. Martin, “Thermodynamic properties of model CdTe/CdSe mixtures,” Molecular Simulation. 2016. link Times cited: 3 Abstract: We report on the thermodynamic properties of binary compound… read moreAbstract: We report on the thermodynamic properties of binary compound mixtures of model groups II–VI semiconductors. We use the recently introduced Stillinger–Weber Hamiltonian to model binary mixtures of CdTe and CdSe. We use molecular dynamics simulations to calculate the volume and enthalpy of mixing as a function of mole fraction. The lattice parameter of the mixture closely follows Vegard's law: a linear relation. This implies that the excess volume is a cubic function of mole fraction. A connection is made with hard sphere models of mixed fcc and zincblende structures. The potential energy exhibits a positive deviation from ideal soluton behaviour; the excess enthalpy is nearly independent of temperatures studied (300 and 533 K) and is well described by a simple cubic function of the mole fraction. Using a regular solution approach (combining non-ideal behaviour for the enthalpy with ideal solution behaviour for the entropy of mixing), we arrive at the Gibbs free energy of the mixture. The Gibbs free energy results indicate that the CdTe and CdSe mixtures exhibit phase separation. The upper consolute temperature is found to be 335 K. Finally, we provide the surface energy as a function of composition. It roughly follows ideal solution theory, but with a negative deviation (negative excess surface energy). This indicates that alloying increases the stability, even for nano-particles. read less NOT USED (high confidence) W.-T. Xu, L. Zhu, Y. Cai, G. Zhang, and B. Li, “Direction dependent thermal conductivity of monolayer phosphorene: parameterization of Stillinger-Weber potential and molecular dynamics study,” arXiv: Mesoscale and Nanoscale Physics. 2015. link Times cited: 70 Abstract: A Stillinger-Weber interatomic potential is parameterized fo… read moreAbstract: A Stillinger-Weber interatomic potential is parameterized for phosphorene. It well reproduces the crystal structure, cohesive energy and phonon dispersion predicted by first-principles calculations. The thermal conductivity of phosphorene is further explored by equilibrium molecular dynamics simulations adopting the optimal set of potential parameters. At room temperature, the intrinsic thermal conductivities along zigzag and armchair directions are about 152.7 and 33.0 W/mK, respectively, with a large anisotropy ratio of five. The remarkably directional dependence of thermal conductivity in phosphorene, consistent with previous reports, is mainly due to the strong anisotropy of phonon group velocities, and weak anisotropy of phonon lifetimes as revealed by lattice dynamics calculations. Moreover, the effective phonon mean free paths at zigzag and armchair directions are about 141.4 and 43.4nm, respectively. read less NOT USED (high confidence) B. Bonef et al., “Atomic arrangement at ZnTe/CdSe interfaces determined by high resolution scanning transmission electron microscopy and atom probe tomography,” Applied Physics Letters. 2015. link Times cited: 15 Abstract: High resolution scanning transmission electron microscopy an… read moreAbstract: High resolution scanning transmission electron microscopy and atom probe tomography experiments reveal the presence of an intermediate layer at the interface between two binary compounds with no common atom, namely, ZnTe and CdSe for samples grown by Molecular Beam Epitaxy under standard conditions. This thin transition layer, of the order of 1 to 3 atomic planes, contains typically one monolayer of ZnSe. Even if it occurs at each interface, the direct interface, i.e., ZnTe on CdSe, is sharper than the reverse one, where the ZnSe layer is likely surrounded by alloyed layers. On the other hand, a CdTe-like interface was never observed. This interface knowledge is crucial to properly design superlattices for optoelectronic applications and to master band-gap engineering. read less NOT USED (high confidence) X. Zhou, M. E. Foster, F. Swol, J. E. Martin, and B. M. Wong, “Analytical Bond-Order Potential for the Cd–Te–Se Ternary System,” Journal of Physical Chemistry C. 2014. link Times cited: 13 NOT USED (high confidence) X. W. Zhou, J. J. Chavez, J. Cruz-Campa, and D. Zubia, “Towards model-guided defect reduction in Cd1−xZnxTe/CdS solar cells: Development of molecular dynamics models,” 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC). 2014. link Times cited: 0 Abstract: Cd1-xZnxTe/CdS solar cells are currently limited by material… read moreAbstract: Cd1-xZnxTe/CdS solar cells are currently limited by material defects. While nano-structuring promises further defect reductions, the materials synthesis and characterization become more challenging. Molecular dynamics models capable of growth simulations enable defects to be explored without assumptions, and can therefore guide nanoscale experiments. Such models are difficult to develop, and are not routinely available in literature for semiconductor compounds. To fill this gap, we have developed growth simulation enabling Stillinger-Weber and bond-order potentials. These new models begin to enable molecular dynamics to be used to explore nano-structured Cd1-xZnxTe/CdS solar cells with reduced defects. read less NOT USED (high confidence) X. Hu, R. Ciaglia, F. Pietrucci, G. A. Gallet, and W. Andreoni, “DFT-derived reactive potentials for the simulation of activated processes: the case of CdTe and CdTe:S.,” The journal of physical chemistry. B. 2014. link Times cited: 2 Abstract: We introduce a new ab initio derived reactive potential for … read moreAbstract: We introduce a new ab initio derived reactive potential for the simulation of CdTe within density functional theory (DFT) and apply it to calculate both static and dynamical properties of a number of systems (bulk solid, defective structures, liquid, surfaces) at finite temperature. In particular, we also consider cases with low sulfur concentration (CdTe:S). The analysis of DFT and classical molecular dynamics (MD) simulations performed with the same protocol leads to stringent performance tests and to a detailed comparison of the two schemes. Metadynamics techniques are used to empower both Car-Parrinello and classical molecular dynamics for the simulation of activated processes. For the latter, we consider surface reconstruction and sulfur diffusion in the bulk. The same procedures are applied using previously proposed force fields for CdTe and CdTeS materials, thus allowing for a detailed comparison of the various schemes. read less NOT USED (definite) B. Li et al., “Pressure compression of CdSe nanoparticles into luminescent nanowires,” Science Advances. 2017. link Times cited: 55 Abstract: Pressure overcomes balanced particle interactions and enable… read moreAbstract: Pressure overcomes balanced particle interactions and enables fine-tuning of nanoparticle lattice, forming new luminescent nanowires. Oriented attachment (OA) of synthetic nanocrystals is emerging as an effective means of fabricating low-dimensional nanoscale materials. However, OA relies on energetically favorable nanocrystal facets to grow nanostructured materials. Consequently, nanostructures synthesized through OA are generally limited to a specific crystal facet in their final morphology. We report our discovery that high-pressure compression can induce consolidation of spherical CdSe nanocrystal arrays, leading to unexpected one-dimensional semiconductor nanowires that do not exhibit the typical crystal facet. In particular, in situ high-pressure synchrotron x-ray scattering, optical spectroscopy, and high-resolution transmission electron microscopy characterizations indicate that by manipulating the coupling between nanocrystals through external pressure, a reversible change in nanocrystal assemblies and properties can be achieved at modest pressure. When pressure is increased above a threshold, these nanocrystals begin to contact one another and consolidate, irreversibly forming one-dimensional luminescent nanowires. High-fidelity molecular dynamics (MD) methods were used to calculate surface energies and simulate compression and coalescence mechanisms of CdSe nanocrystals. The MD results provide new insight into nanowire assembly dynamics and phase stability of nanocrystalline structures. read less NOT USED (definite) Z. Fan et al., “A transferable force field for CdS-CdSe-PbS-PbSe solid systems.,” The Journal of chemical physics. 2014. link Times cited: 19 Abstract: A transferable force field for the PbSe-CdSe solid system us… read moreAbstract: A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., "Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth," Nano Lett. 14, 3661-3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange. read less
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