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.
59 Citations (19 used)
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USED (high confidence) J. Dawson, H. Chen, and I. Tanaka, “First-principles calculations of oxygen vacancy formation and metallic behavior at a β-MnO2 grain boundary.,” ACS applied materials & interfaces. 2015. link Times cited: 45 Abstract: Nanostructured MnO2 is renowned for its excellent energy sto… read moreAbstract: Nanostructured MnO2 is renowned for its excellent energy storage capability and high catalytic activity. While the electronic and structural properties of MnO2 surfaces have received significant attention, the properties of the grain boundaries (GBs) and their contribution to the electrochemical performance of the material remains unknown. Through density functional theory (DFT) calculations, the structure and electronic properties of the β-MnO2 Σ 5(210)/[001] GB are studied. Our calculations show this low energy GB has a significantly reduced band gap compared to the pristine material and that the formation of oxygen vacancies produces spin-polarized states that further reduce the band gap. Calculated formation energies of oxygen vacancy defects and Mn reduction at the GB core are all lower than the equivalent bulk value and in some cases lower than values recently calculated for β-MnO2 surfaces. Oxygen vacancy formation is also shown to produce a metallic behavior at the GB with defect charge distributed over a number of oxygen and manganese sites. The low energies of oxygen defect formation and the potential creation of conductive GB pathways are likely to be important to the electrochemical performance of β-MnO2. read less USED (high confidence) A. Barnard, “Modelling of nanoparticles: approaches to morphology and evolution,” Reports on Progress in Physics. 2010. link Times cited: 171 Abstract: As we learn more about the physics, chemistry and engineerin… read moreAbstract: As we learn more about the physics, chemistry and engineering of materials at the nanoscale, we find that the development of a complete understanding is not (in general) possible using one technique alone. Computer simulations provide a very valuable addition to our scientific repertoire, but it is not immediately intuitive which of the many methods available are right for a given problem. In this paper, various computational approaches are described as they apply to the study of the structure and formation of discrete inorganic nanoparticles. To illustrate how these methods are best used, results of studies from many research groups are reviewed, and informal case studies are constructed on carbon, titania and gold nanoparticles. read less USED (high confidence) T. Sayle, P. Ngoepe, and D. Sayle, “Simulating mechanical deformation in nanomaterials with application for energy storage in nanoporous architectures.,” ACS nano. 2009. link Times cited: 24 Abstract: Central to porous nanomaterials, with applications spanning … read moreAbstract: Central to porous nanomaterials, with applications spanning catalysts to fuel cells is their (perceived) "fragile" structure, which must remain structurally intact during application lifespan. Here, we use atomistic simulation to explore the mechanical strength of a porous nanomaterial as a first step to characterizing the structural durability of nanoporous materials. In particular, we simulate the mechanical deformation of mesoporous Li-MnO(2) under stress using molecular dynamics simulation. Specifically, such rechargeable Li-ion battery materials suffer volume changes during charge/discharge cycles as Li ions are repeatedly inserted and extracted from the host beta-MnO(2) causing failure as a result of localized stress. However, mesoporous beta-MnO(2) does not suffer structural collapse during cycling. To explain this behavior, we generate a full atomistic model of mesoporous beta-MnO(2) and simulate localized stress associated with charge/discharge cycles. We calculate that mesoporous beta-MnO(2) undergoes a volume expansion of about 16% when Li is fully intercalated, which can only be sustained without structural collapse, if the nanoarchitecture is symmetrically porous, enabling elastic deformation during intercalation. Conversely, we predict that unsymmetric materials, such as nanoparticulate beta-MnO(2), deform plastically, resulting in structural collapse of (Li) storage sites and blocked transport pathways; animations revealing elastic and plastic deformation mechanisms under mechanical load and crystallization of mesoporous Li-MnO(2) are presented at the atomistic level. read less USED (high confidence) T. Sayle, S. C. Parker, and D. Sayle, “Oxygen transport in unreduced, reduced and Rh(III)-doped CeO2 nanocrystals.,” Faraday discussions. 2007. link Times cited: 21 Abstract: Ceria, CeO2, based materials are a major (active) component … read moreAbstract: Ceria, CeO2, based materials are a major (active) component of exhaust catalysts and promising candidates for solid oxide fuel cells. In this capacity, oxygen transport through the material is pivotal. Here, we explore whether oxygen transport is influenced (desirably increased) compared with transport within the bulk parent material by traversing to the nanoscale. In particular, atomistic models for ceria nanocrystals, including perfect: CeO2; reduced: CeO1.95 and doped: Rh0.1Ce0.9O1.95, have been generated. The nanocrystals were about 8 nm in diameter and each comprised about 16,000 atoms. Oxygen transport can also be influenced, sometimes profoundly, by microstructural features such as dislocations and grain-boundaries. However, these are difficult to generate within an atomistic model using, for example, symmetry operations. Accordingly, we crystallised the nanocrystals from an amorphous precursor, which facilitated the evolution of a variety of microstructures including: twin-boundaries and more general grain-boundaries and grain-junctions, dislocations and epitaxy, isolated and associated point defects. The shapes of the nanocrystals are in accord with HRTEM data and comprise octahedral morphologies with {111} surfaces, truncated by (dipolar) {100} surfaces together with a complex array of steps, edges and corners. Oxygen transport data was then calculated using these models and compared with data calculated previously for CeO1.97/ YSZ thin films and the (bulk) parent material, CeO197. Oxygen transport was calculated to increase in the order: CeO2 nanocrystal < (reduced) CeO1.95 nanocrystal approximately Rh0.1Ce0.9O1.95 nanocrystal < CeO1.97/YSZ thin film < (reduced) CeO1.97 (bulk) parent material; the mechanism was determined to be primarily vacancy driven. Our findings indicate that reducing one- (thin film) or especially three- (nanocrystal) dimensions to the nanoscale may prove deleterious to oxygen transport. Conversely, we observed dynamic evolution and annihilation of surface vacancies via surface oxygens migrating to the bulk of the nanocrystal; the vacancies left are then filled by other oxygens moving to the surface. Coupled with previous simulation studies, in which we calculated that oxygen extraction from the surface of a ceria nanocrystal was energetically easier compared with the bulk surface, our calculations predict that ceria nanocrystals would facilitate effective oxidative catalysis. This study describes framework simulation procedures, which can be used in partnership with experiment, to explore transport in nanocrystalline ionic systems, which include complex microstructures. Such data can provide predictions for experiment or help reduce the number of experiments required. read less USED (low confidence) T. Mogashoa, R. Ledwaba, and P. Ngoepe, “Analysing the Implications of Charging on Nanostructured Li2MnO3 Cathode Materials for Lithium-Ion Battery Performance,” Materials. 2022. link Times cited: 0 Abstract: Capacity degradation and voltage fade of Li2MnO3 during cycl… read moreAbstract: Capacity degradation and voltage fade of Li2MnO3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li2MnO3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li2−xMnO3−x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn2O4, Li2MnO3, and LiMnO2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18–25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li1.00MnO2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li2MnO3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen. read less USED (low confidence) A. G. Newton and K. Kwon, “Classical mechanical simulations of layer- and tunnel-structured manganese oxide minerals,” Geochimica et Cosmochimica Acta. 2020. link Times cited: 12 USED (low confidence) R. Ledwaba, D. Sayle, and P. Ngoepe, “Atomistic Simulation and Characterization of Spinel Li1+xMn2O4 (0 ≤ x ≤ 1) Nanoparticles.” 2020. link Times cited: 10 Abstract: Lithium-ion batteries, comprising nanoparticulate Ni–Mn–Co (… read moreAbstract: Lithium-ion batteries, comprising nanoparticulate Ni–Mn–Co (NMC) cathodes that have been used to power electric vehicles, can be improved by blending NMC with Li–Mn–O (LMO). However, LMO undergoes ... read less USED (low confidence) B. Shibiri, R. Ledwaba, and P. Ngoepe, “Discharge induced structural variation of simulated bulk Li1+xMn2O4 (0 ≤ x ≤ 1),” Optical Materials. 2019. link Times cited: 3 USED (low confidence) A. G. Newton and K. Kwon, “Molecular simulations of hydrated phyllomanganates,” Geochimica et Cosmochimica Acta. 2018. link Times cited: 9 USED (low confidence) M. Matshaba, D. Sayle, T. Sayle, and P. Ngoepe, “Amorphisation and recrystallisation study of lithium intercalation into TiO2 nano-architecture.,” IOP Conference Series: Materials Science and Engineering. 2017. link Times cited: 0 Abstract: Titanium dioxide is playing an increasingly significant role… read moreAbstract: Titanium dioxide is playing an increasingly significant role in easing environmental and energy concerns. Its rich variety of polymorphic crystal structures has facilitated a wide range of applications such as photo-catalysis, photo-splitting of water, photoelectrochromic devices, insulators in metal oxide, semiconductors devices, dye sensitized solar cells (DSSCs) (energy conversions), rechargeable lithium batteries (electrochemical storage). The complex structural aspects in nano TiO2, are elucidated by microscopic visualization and quantification of the microstructure for electrode materials, since cell performance and various aging mechanisms depend strongly on the appearance and changes in the microstructure. Recent studies on MnO2 have demonstrated that amorphisation and recrystallisation simulation method can adequately generate various nanostructures, for Li-ion battery compounds. The method was also previously employed to produce nano-TiO2. In the current study, the approach is used to study lithiated nanoporous structure for TiO2 which have been extensively studied experimentally, as mentioned above. Molecular graphic images showing microstructural features, including voids and channels have accommodated lithium’s during lithiation and delithiation. Preliminary lithiation of TiO2 will be considered. read less USED (low confidence) S. Kerisit, A. Chaka, T. Droubay, and E. Ilton, “Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed Mn/Ti Oxides,” Journal of Physical Chemistry C. 2014. link Times cited: 14 Abstract: Mixed Mn/Ti oxides present attractive physicochemical proper… read moreAbstract: Mixed Mn/Ti oxides present attractive physicochemical properties such as their ability to accommodate Li for application in Li-ion batteries. In this work, atomic parameters for Mn were developed to extend an existing shell model of the Li–Ti–O system and allow simulations of pure and lithiated Mn and mixed Mn/Ti oxide polymorphs. The shell model yielded good agreement with experimentally derived structures (i.e., lattice parameters and interatomic distances) and represented an improvement over existing potential models. The shell model was employed in molecular dynamics (MD) simulations of Li diffusion in the 1 × 1 c-direction channels of LixMn1–yTiyO2 with the rutile structure, where 0 ≤ x ≤ 0.25 and 0 ≤ y ≤ 1. In the infinite dilution limit, the arrangement of Mn and Ti ions in the lattice was found to have a significant effect on the activation energy for Li diffusion in the c channels due to the destabilization of half of the interstitial octahedral sites. Anomalous diffusion was demonstrated for Li ... read less USED (low confidence) D. Tompsett and M. Islam, “Electrochemistry of Hollandite α-MnO2: Li-Ion and Na-Ion Insertion and Li2O Incorporation,” Chemistry of Materials. 2013. link Times cited: 164 Abstract: MnO2 is attracting considerable interest in the context of r… read moreAbstract: MnO2 is attracting considerable interest in the context of rechargeable batteries, supercapacitors, and Li–O2 battery applications. This work investigates the electrochemical properties of hollandite α-MnO2 using density functional theory with Hubbard U corrections (DFT+U). The favorable insertion sites for Li-ion and Na-ion insertion are determined, and we find good agreement with measured experimental voltages. By explicit calculation of the phonons we suggest multiple insertion sites are accessible in the dilute limit. Significant structural changes in α-(Li,Na)xMnO2 during ion insertion are demonstrated by determining the low energy structures. The significant distortions to the unit cell and Mn coordination are likely to be active in causing the observed degradation of α-MnO2 with cycling. The presence of Li2O in the structure reduces these distortions significantly and is the probable cause for the good experimental cycling stability of α-[0.143Li2O]-MnO2. However, the presence of Na2O is less effec... read less USED (low confidence) D. Tompsett, S. C. Parker, P. Bruce, and M. Islam, “Nanostructuring of β-MnO2: The Important Role of Surface to Bulk Ion Migration,” Chemistry of Materials. 2013. link Times cited: 93 Abstract: Manganese oxide materials are attracting considerable intere… read moreAbstract: Manganese oxide materials are attracting considerable interest for clean energy storage applications such as rechargeable Li ion and Li−air batteries and electrochemical capacitors. The electrochemical behavior of nanostructured mesoporous β-MnO2 is in sharp constrast to the bulk crystalline system, which can intercalate little or no lithium; this is not fully understood on the atomic scale. Here, the electrochemical properties of β-MnO2 are investigated using density functional theory with Hubbard U corrections (DFT+U). We find good agreement between the measured experimental voltage, 3.0 V, and our calculated value of 3.2 V. We consider the pathways for lithium migration and find a small barrier of 0.17 eV for bulk β-MnO2, which is likely to contribute to its good performance as a lithium intercalation cathode in the mesoporous form. However, by explicit calculation of surface to bulk ion migration, we find a higher barrier of >0.6 eV for lithium insertion at the (101) surface that dominates the equilibrium morphology. This is likely to limit the practical use of bulk samples, and demonstrates the quantitative importance of surface to bulk ion migration in Li ion cathodes and supercapacitors. On the basis of the calculation of the electrostatic potential near the surface, we propose an efficient method to screen systems for the importance of surface migration effects. Such insight is valuable for the future optimization of manganese oxide nanomaterials for energy storage devices. read less USED (low confidence) J. Anwar and D. Zahn, “Uncovering molecular processes in crystal nucleation and growth by using molecular simulation.,” Angewandte Chemie. 2011. link Times cited: 216 Abstract: Exploring nucleation processes by molecular simulation provi… read moreAbstract: Exploring nucleation processes by molecular simulation provides a mechanistic understanding at the atomic level and also enables kinetic and thermodynamic quantities to be estimated. However, whilst the potential for modeling crystal nucleation and growth processes is immense, there are specific technical challenges to modeling. In general, rare events, such as nucleation cannot be simulated using a direct "brute force" molecular dynamics approach. The limited time and length scales that are accessible by conventional molecular dynamics simulations have inspired a number of advances to tackle problems that were considered outside the scope of molecular simulation. While general insights and features could be explored from efficient generic models, new methods paved the way to realistic crystal nucleation scenarios. The association of single ions in solvent environments, the mechanisms of motif formation, ripening reactions, and the self-organization of nanocrystals can now be investigated at the molecular level. The analysis of interactions with growth-controlling additives gives a new understanding of functionalized nanocrystals and the precipitation of composite materials. read less USED (low confidence) R. R. Maphanga, D. Sayle, T. Sayle, and P. Ngoepe, “Amorphization and recrystallization study of lithium insertion into manganese dioxide.,” Physical chemistry chemical physics : PCCP. 2011. link Times cited: 17 Abstract: Various polymorphs of MnO(2) are widely used as electrode ma… read moreAbstract: Various polymorphs of MnO(2) are widely used as electrode materials in Li/MnO(2) batteries. Electrolytic manganese dioxide (EMD) is the most electrochemically active form of MnO(2) and is very difficult to characterize. Their structural details are still largely unknown owing to the poor quality of X-ray diffraction (XRD) patterns obtained from most MnO(2) samples. Simulated amorphisation and crystallization technique was used to derive microstructural models for Li-MnO(2) which included most microstructural details that one would expect to find in the real material. Specifically, pyrolusite-MnO(2), comprising about 25,000 atoms, was amorphised (strain-induced) under molecular dynamics (MD) and different concentrations of lithium ions were inserted. Each system was then crystallized under MD simulation. The resulting models conformed to the pyrolusite polymorph, with microstructural features including: extensive micro-twinning and more general grain-boundaries, stacking faults, dislocations and isolated point defects and defect clusters. Molecular graphical images, showing the atom positions for the microstructural features together with simulated XRD patterns they give rise to, are presented and compared with measured XRD. The calculated XRD are in accord with experiment thus validating the structural models. read less USED (low confidence) R. R. Maphanga, S. C. Parker, and P. Ngoepe, “Atomistic simulation of the surface structure of electrolytic manganese dioxide,” Surface Science. 2009. link Times cited: 34 USED (low confidence) T. Sayle, C. Catlow, R. Maphanga, P. Ngoepe, and D. Sayle, “Evolving microstructure in MnO 2 using amorphisation and recrystallisation,” Journal of Crystal Growth. 2006. link Times cited: 12 USED (low confidence) D. Sayle and T. Sayle, “Atomistic Models and Molecular Dynamics.” 2006. link Times cited: 1 Abstract: Here we show how atomistic computer simulation can help expe… read moreAbstract: Here we show how atomistic computer simulation can help experiment unravel the rich structural complexity of oxide nanomaterials and, ultimately, aid the fabrication of nanomaterials with improved, tuneable or indeed new properties. We first explore the simulation methodologies: energy minimisation, monte-carlo, genetic algorithms and molecular dynamics together with the potential models used to describe the interactions between metal and oxide ions. These tools can be used to generate realistic structures that include all the essential microstructural features observed experimentally, such as surface structure (morphology, surface energy, faceting, surface steps, corners and edges), grain-boundaries and dislocations, intrinsic and extrinsic point defects and epitaxy. We show how the theoretician is able to capture all these (experimentally observed) structural details by attempting to simulate crystallisation. Equipped with realistic models, important properties can be calculated, including: electronic, chemical (catalytic activity, ionic diffusion and conductivity) and mechanical (hardness, elastic constants). This is illustrated by calculating the ease of oxygen extraction from the surface of a CeO2 nanocrystal compared with the bulk parent material with implications for oxidative catalysis. Throughout this chapter we emphasise the importance of molecular graphics – a much maligned and underrated tool – but without which, the generation of much of the simulation and experimental data would not have been possible. read less USED (low confidence) D. Hlungwani, R. Ledwaba, and P. Ngoepe, “Simulated synthesis and atomic-level structural characterization of LiNi2O4,” MATEC Web of Conferences. 2023. link Times cited: 0 Abstract: LiMn2O4 is a promising cathode material for advancing lithiu… read moreAbstract: LiMn2O4 is a promising cathode material for advancing lithium-ion batteries due to its high-rate capabilities and high operating voltages. However, it suffers capacity fading due to the loss of manganese and lattice instabilities linked to Mn3+ during cycling. The simulated synthesis technique has been used to generate LiNi2O4 models rich in microstructural features that evolve during the crystal growth process. The microstructural features can be linked to the electrochemical performance and properties of LiNi2O4, which will guide the doping of LiMn2O4 spinel with Ni. Substitution of a small amount of manganese with nickel has been proposed as one of the solutions for reducing capacity loss. The LiNi2O4 spinel structure was synthesized successfully with the simulated amorphization and recrystallization technique. The RDF functions indicated the average Ni – O bond length of ~1.925 Å which is comparable to the Ni – O average bond length of ~1.923 Å synthesized by Thomas M.G.SR and co-workers. read less NOT USED (low confidence) J. C. M. Madrid and K. Ghuman, “Disorder in energy materials and strategies to model it,” Advances in Physics: X. 2021. link Times cited: 1 Abstract: ABSTRACT The functionality of the materials used for energy … read moreAbstract: ABSTRACT The functionality of the materials used for energy applications is critically determined by the physical properties of small active regions such as dopants, dislocations, interfaces, grain boundaries, etc. The capability to manipulate and utilize the inevitable disorder in materials, whether due to the finite-dimensional defects (such as vacancies, dopants, grain boundaries) or due to the complete atomic randomness (as in amorphous materials), can bring innovation in designing energy materials. With the increase in computational material science capabilities, it is now possible to understand the complexity present in materials due to various degrees of disorder resulting in pathways required for optimizing their efficiencies. This article provides a critical overview of such computational advancements specifically for designing realistic materials with various types of disorders for sustainable energy applications such as catalysts and electrochemical devices. The ultimate goal is to gain a thorough knowledge of the traditional approaches (implemented via tools such as density functional theory, and molecular dynamics) as well as modern approaches such as machine learning that exist for modeling the disorder present in materials, thereby identify the future opportunities for energy materials design and discovery. Graphical abstract read less NOT USED (low confidence) L. M. Morgan, M. Molinari, A. Corrias, and D. Sayle, “Protecting Ceria Nanocatalysts-The Role of Sacrificial Barriers.,” ACS applied materials & interfaces. 2018. link Times cited: 6 Abstract: Forces acting on a functional nanomaterial during operation … read moreAbstract: Forces acting on a functional nanomaterial during operation can cause plastic deformation and extinguish desirable catalytic activities. Here, we show that sacrificial materials, introduced into the catalytic composite device, can absorb some of the imposed stress and protect the structural integrity and hence the activity of the functional component. Specifically, we use molecular dynamics to simulate uniaxial stress on a ceria (CeO2) nanocube, an important functional material with respect to oxidative catalysis, such as the conversion of CO to CO2. We predict that the nanocube, protected by a "soft" BaO or "hard" MgO sacrificial barrier, is able to withstand 40.1 or 26.5 GPa, respectively, before plastic deformation destroys the structure irreversibly; the sacrificial materials, BaO and MgO, capture 71 and 54% of the stress, respectively. In comparison, the unprotected nanoceria catalyst deforms plastically at only 2.5 GPa. Furthermore, modeling reveals the deformation mechanisms and the importance of microstructural features, insights that are difficult to measure experimentally. read less NOT USED (low confidence) Y.-F. Li, S. Zhu, and Z. Liu, “Reaction Network of Layer-to-Tunnel Transition of MnO2.,” Journal of the American Chemical Society. 2016. link Times cited: 104 Abstract: As a model system of 2-D oxide material, layered δ-MnO2 has … read moreAbstract: As a model system of 2-D oxide material, layered δ-MnO2 has important applications in Li ion battery systems. δ-MnO2 is also widely utilized as a precursor to synthesize other stable structure variants in the MnO2 family, such as α-, β-, R-, and γ-phases, which are 3-D interlinked structures with different tunnels. By utilizing the stochastic surface walking (SSW) pathway sampling method, we here for the first time resolve the atomistic mechanism and the kinetics of the layer-to-tunnel transition of MnO2, that is, from δ-MnO2 to the α-, β-, and R-phases. The SSW sampling determines the lowest-energy pathway from thousands of likely pathways that connects different phases. The reaction barriers of layer-to-tunnel phase transitions are found to be low, being 0.2-0.3 eV per formula unit, which suggests a complex competing reaction network toward different tunnel phases. All the transitions initiate via a common shearing and buckling movement of the MnO2 layer that leads to the breaking of the Mn-O framework and the formation of Mn(3+) at the transition state. Important hints are thus gleaned from these lowest-energy pathways: (i) the large pore size product is unfavorable for the entropic reason; (ii) cations are effective dopants to control the kinetics and selectivity in layer-to-tunnel transitions, which in general lowers the phase transition barrier and facilitates the creation of larger tunnel size; (iii) the phase transition not only changes the electronic structure but also induces the macroscopic morphology changes due to the interfacial strain. read less NOT USED (low confidence) S. Woodley, “Nanoclusters and nanoparticles.” 2016. link Times cited: 7 Abstract: Interest in the synthesis and characterization of nanopartic… read moreAbstract: Interest in the synthesis and characterization of nanoparticles has been driven in part by their increasing use in a wide range of applications in electronics, energy conversion, and catalysis, where their large surface-area-to-volume ratio is beneficial [1]. Three interesting examples are vanadia, titania, and silver-based particles. The vanadium dioxide and titanium dioxide–based particles are tuned to absorb light within a certain range of frequencies, which are used in smart windows and sunscreen lotions, respectively. Silver nanoparticles, which have antibacterial properties, are useful in combating infections once the particles are incorporated in materials used in medical devices and hospital equipment; and they are exploited in our everyday life: in socks and shoes to help prevent odours. Moreover, interest in nanoparticles is driven by the need to understand and gain insight into the atomic mechanism of crystal nucleation and the early stages of crystal growth; see, for example, the perspective article on modeling nanoclusters and nucleation by Catlow et al. [2] and the review on experimental and computational studies of ZnS nanostructures by Hamad et al. [3]. By definition, nanoparticles are particles between 1 and 100 nm in size. Reducing the size of the particle—by the removal of atoms as opposed to varying applied pressure—can lead to a structural phase change and, in some cases, to an atomic structure that differs dramatically from that of the bulk phase(s). Nanoparticles at the bottom of this range or below, composed of less than ~100 atoms, are referred to as nanoclusters. The structural diversity at the nanoscale is well demonstrated by zinc sulfide, a wide bandgap semiconductor that is used in optoelectronics and as a photocatalyst. In bulk, ZnS can adopt either the sphalerite (cubic) or wurtzite (hexagonal) structure. The two phases coexist in nature, but sphalerite is the most stable bulk form under ambient conditions, whereas for smaller nanoparticles, the wurtzite phase becomes more thermodynamically stable [4]; moreover, nanoparticles with mixed cubic and hexagonal stacking have been synthesized [5]. For the smallest particles, or nanoclusters of ZnS, the atomic structures no longer resemble a cut taken from any bulk phase; see later. Such nanoclusters are readily created by either laser ablation of the bulk structure or nucleation in solution [6–8]. Critically, for particles with sizes below 5 and 10 nm, no clear diffraction patterns are obtainable, and accurate structure determination of these small particles using standard x-ray diffraction techniques starts to fail. Diffraction techniques require a target of sufficient size, a large single crystal or a powder formed of smaller crystals (ideally all with the same crystalline phase). Structure determination of nanoclusters currently relies on computational techniques to predict the atomic structure for each size as the structure is dependent upon the number of atoms. Matching observed and predicted properties gives confidence in the current structural predictions. read less NOT USED (low confidence) A. Erlebach, H.-D. Kurland, J. Grabow, F. Müller, and M. Sierka, “Structure evolution of nanoparticulate Fe2O3.,” Nanoscale. 2015. link Times cited: 32 Abstract: The atomic structure and properties of nanoparticulate Fe2O3… read moreAbstract: The atomic structure and properties of nanoparticulate Fe2O3 are characterized starting from its smallest Fe2O3 building unit through (Fe2O3)n clusters to nanometer-sized Fe2O3 particles. This is achieved by combining global structure optimizations at the density functional theory level, molecular dynamics simulations by employing tailored, ab initio parameterized interatomic potential functions and experiments. With the exception of nearly tetrahedral, adamantane-like (Fe2O3)2 small (Fe2O3)n clusters assume compact, virtually amorphous structures with little or no symmetry. For n = 2-5 (Fe2O3)n clusters consist mainly of two- and three-membered Fe-O rings. Starting from n = 5 they increasingly assume tetrahedral shape with the adamantane-like (Fe2O3)2 unit as the main building block. However, the small energy differences between different isomers of the same cluster-size make precise structural assignment for larger (Fe2O3)n clusters difficult. The tetrahedral morphology persists for Fe2O3 nanoparticles with up to 3 nm in diameter. Simulated crystallization of larger nanoparticles with diameters of about 5 nm demonstrates pronounced melting point depression and leads to formation of ε-Fe2O3 single crystals with hexagonal morphology. This finding is in excellent agreement with the results obtained for Fe2O3 nanopowders generated by laser vaporization and provides the first direct indication that ε-Fe2O3 may be thermodynamically the most stable phase in this size regime. read less NOT USED (low confidence) T. Sayle, F. Caddeo, N. Monama, K. Kgatwane, P. Ngoepe, and D. Sayle, “Origin of electrochemical activity in nano-Li2MnO3; stabilization via a ’point defect scaffold’.,” Nanoscale. 2015. link Times cited: 18 Abstract: Molecular dynamics (MD) simulations of the charging of Li2Mn… read moreAbstract: Molecular dynamics (MD) simulations of the charging of Li2MnO3 reveal that the reason nanocrystalline-Li2MnO3 is electrochemically active, in contrast to the parent bulk-Li2MnO3, is because in the nanomaterial the tunnels, in which the Li ions reside, are held apart by Mn ions, which act as a pseudo 'point defect scaffold'. The Li ions are then able to diffuse, via a vacancy driven mechanism, throughout the nanomaterial in all spatial dimensions while the 'Mn defect scaffold' maintains the structural integrity of the layered structure during charging. Our findings reveal that oxides, which comprise cation disorder, can be potential candidates for electrodes in rechargeable Li-ion batteries. Moreover, we propose that the concept of a 'point defect scaffold' might manifest as a more general phenomenon, which can be exploited to engineer, for example, two or three-dimensional strain within a host material and can be fine-tuned to optimize properties, such as ionic conductivity. read less NOT USED (low confidence) H. Liu, X. Ma, L. Li, Z. Hu, P. Guo, and Y. Jiang, “The catalytic pyrolysis of food waste by microwave heating.,” Bioresource technology. 2014. link Times cited: 103 NOT USED (low confidence) H. Naderi, M. Ara, H. Zebarjadan, J. Saydi, and A. Javidan, “Nonlinear response of nano-particles birnessite-type Manganese oxide (γ-MnO2),” Optik. 2013. link Times cited: 11 NOT USED (low confidence) P. Ngoepe, R. R. Maphanga, and D. Sayle, “Toward the Nanoscale.” 2013. link Times cited: 0 NOT USED (low confidence) P. Yadav, R. Olsson, and M. Jonsson, “Synthesis and characterization of MnO2 colloids,” Radiation Physics and Chemistry. 2009. link Times cited: 12 NOT USED (low confidence) T. Sayle, R. R. Maphanga, P. Ngoepe, and D. Sayle, “Predicting the electrochemical properties of MnO2 nanomaterials used in rechargeable li batteries: simulating nanostructure at the atomistic level.,” Journal of the American Chemical Society. 2009. link Times cited: 68 Abstract: Nanoporous beta-MnO2 can act as a host lattice for the inser… read moreAbstract: Nanoporous beta-MnO2 can act as a host lattice for the insertion and deinsertion of Li with application in rechargeable lithium batteries. We predict that, to maximize its electrochemical properties, the beta-MnO2 host should be symmetrically porous and heavily twinned. In addition, we predict that there exists a "critical (wall) thickness" for MnO2 nanomaterials above which the strain associated with Li insertion is accommodated via a plastic, rather than elastic, deformation of the host lattice leading to property fading upon cycling. We predict that this critical thickness lies between 10 and 100 nm for beta-MnO2 and is greater than 100 nm for alpha-MnO2: the latter accommodates 2 x 2 tunnels compared with the smaller 1 x 1 tunnels found in beta-MnO2. This prediction may help explain why certain (nano)forms of MnO2 are electrochemically active, while others are not. Our predictions are based upon atomistic models of beta-MnO2 nanomaterials. In particular, a systematic strategy, analogous to methods widely and routinely used to model crystal structure, was used to generate the nanostructures. Specifically, the (space) symmetry associated with the nanostructure coupled with basis nanoparticles was used to prescribe full atomistic models of nanoparticles (0D), nanorods (1D), nanosheets (2D), and nanoporous (3D) architectures. For the latter, under MD simulation, the amorphous nanoparticles agglomerate together with their periodic neighbors to formulate the walls of the nanomaterial; the particular polymorphic structure was evolved using simulated amorphization and crystallization. We show that our atomistic models are in accord with experiment. Our models reveal that the periodic framework architecture, together with microtwinning, enables insertion of Li anywhere on the (internal) surface and facilitates Li transport in all three spatial directions within the host lattice. Accordingly, the symmetrically porous MnO2 can expand and contract linearly and crucially elastically under charge/discharge. We also suggest tentatively that our predictions for MnO2 are more general in that similar arguments may apply to other nanomaterials, which might expand and contract elastically upon charging/discharging. read less NOT USED (low confidence) J. Fei et al., “Controlled Preparation of MnO2 Hierarchical Hollow Nanostructures and Their Application in Water Treatment,” Advanced Materials. 2008. link Times cited: 667 Abstract: Manganese oxides are of considerable importance in technolog… read moreAbstract: Manganese oxides are of considerable importance in technological applications, including ion-exchange, molecular adsorption, catalysis, and electrochemical supercapacitors owing to their structural flexibility combined with novel chemical and physical properties. Up to now, various nanostructures of MnO2, such as nanoparticles, [6] nanorods/-belts/-wires/-tubes/fibers, nanosheets, mesoporous/molecular sieves and branched structures, urchins/orchids, and other hierarchical structures have been synthesized by different methods. Over the past years, fabrication of hierarchical hollow nanostructures has attracted significant interest because of their widespread potential applications in catalysis, drug delivery, acoustic insulation, photonic crystals, and other areas. Until now, the general approach for preparation of hollow structures has involved the use of various removable or sacrificial templates, referred to as “hard”, such as monodispersed silica, polymer latex spheres and reducing metal nanoparticles, as well as “soft” ones, for example, emulsion droplets/ micelles and gas bubbles. Furthermore, lots of one-pot template-free methods for generating hollow inorganic microand nanostructures have been developed employing novel mechanisms, including the nanoscale corrosion-based insideout evacuation and Kirkendall effect. Recently, rhombododecahedral silver cages have been prepared by self-assembly coupled with the precursor crystal-templating approach. By treating the external morphologies of hollow structures, unique properties can be obtained. Thus, it is desirable to develop easy methods to control the morphologies of assembled systems with well-defined hierarchical structures. Herein, we report a simple controlled preparation of hierarchical hollow microspheres and microcubes of MnO2 nanosheets through self-assembly with an intermediate crystaltemplating process. As shown in Figure 1, the synthesis is performed by a three-step process. Particularly, discrete spherical and cubic hollow MnO2 nanostructures with controlled morphologies can be prepared by changing the morphologies of MnCO3 precursors, which can be simply obtained by adding the (NH4)2SO4 solution in the reaction system, and the read less NOT USED (low confidence) L. Li, Y. Pan, L. Chen, and G. Li, “One-dimensional α-MnO2: Trapping chemistry of tunnel structures, structural stability, and magnetic transitions,” Journal of Solid State Chemistry. 2007. link Times cited: 85 NOT USED (low confidence) Y. Luo, “Preparation of MnO2 nanoparticles by directly mixing potassium permanganate and polyelectrolyte aqueous solutions,” Materials Letters. 2007. link Times cited: 69 NOT USED (low confidence) D. Sayle, “From nanoparticles to mesoporous materials.” 2018. link Times cited: 1 NOT USED (low confidence) S. Woodley and S. Bromley, “Introduction to modeling nanoclusters and nanoparticles.” 2018. link Times cited: 2 NOT USED (low confidence) R. Maphanga and P. Ngoepe, “Computational Modelling as a Value Add in Energy Storage Materials.” 2016. link Times cited: 1 NOT USED (low confidence) T. Zhang, “Water treatment using one-dimensional manganese oxide based materials.” 2013. link Times cited: 0 NOT USED (low confidence) M. Lundstrom, P. Cummings, and M. Alam, “Investigative Tools: Theory, Modeling, and Simulation.” 2011. link Times cited: 4 NOT USED (low confidence) A. Seyed-Razavi, I. Snook, and A. Barnard, “Origin of nanomorphology: does a complete theory of nanoparticle evolution exist?,” Journal of Materials Chemistry. 2010. link Times cited: 60 Abstract: Nanotechnology is a relatively new field that can be employe… read moreAbstract: Nanotechnology is a relatively new field that can be employed to deliver substantial advances in most disciplines. Nanoparticles and nanostructures are of particular interest as their characteristics on the nanoscale are different to that of their bulk counterparts. Therefore, it is highly desirable to observe the evolution of these minute structures so that we can gain insight into how one may tailor specific characteristics, for given applications. A theoretical model, complete in its analysis of the various phenomena that occur on the nanoscale, which provide sufficiently accurate results compared to that of experimentation would be invaluable to the materials science and industry. read less NOT USED (high confidence) L. M. Morgan et al., “From Atoms to Cells: Multiscale Modeling of LiNixMnyCozO2 Cathodes for Li-Ion Batteries,” ACS Energy Letters. 2021. link Times cited: 9 Abstract: First–generation cathodes for commercial lithium–ion batteri… read moreAbstract: First–generation cathodes for commercial lithium–ion batteries are based on layered transition-metal oxides. Research on ternary compounds, such as LiCoO 2 , evolved into mixed–metal systems, notably Li(Ni,Mn,Co)O 2 (NMC), which allows significant tuning of the physical properties. Despite widespread application in commercial devices, the fundamental understanding of NMC is incomplete. Here, we review the latest insights from multiscale modelling, bridging between the redox phenomena that occur at an atomistic level to the transport of ions and electrons across an operating device. We discuss changes in the electronic and vibrational structure through the NMC compositional space and how these link to continuum models of electrochemical charge/discharge cycling. Finally, we outline the remaining challenges for predictive models of high–performance batteries, including capturing the relevant device bottle-necks and chemical degradation processes, such as oxygen evolution. read less NOT USED (high confidence) S. Woodley, G. Day, R. Catlow, and R. Catlow, “Structure prediction of crystals, surfaces and nanoparticles,” Philosophical Transactions of the Royal Society A. 2020. link Times cited: 20 Abstract: We review the current techniques used in the prediction of c… read moreAbstract: We review the current techniques used in the prediction of crystal structures and their surfaces and of the structures of nanoparticles. The main classes of search algorithm and energy function are summarized, and we discuss the growing role of methods based on machine learning. We illustrate the current status of the field with examples taken from metallic, inorganic and organic systems. This article is part of a discussion meeting issue ‘Dynamic in situ microscopy relating structure and function’. read less NOT USED (high confidence) Y. Chen, H. Cong, Y. Shen, and B. Yu, “Biomedical application of manganese dioxide nanomaterials,” Nanotechnology. 2020. link Times cited: 29 Abstract: Manganese dioxide nanomaterial is a new type of inorganic na… read moreAbstract: Manganese dioxide nanomaterial is a new type of inorganic nanomaterial offering numerous advantages: simple preparation, low cost, and environmental friendliness. This review summarizes the traditional and novel synthetic methods for manganese dioxide nanomaterials and mainly discusses their potential in biomedical applications. Manganese dioxide nanomaterials are mainly used as drug carriers in tumor therapy. In recent years, the construction of multifunctional nano-platforms using manganese dioxide has gradually improved. The main mechanism is that manganese dioxide nanomaterials can combine with reactive oxygen species in the tumor microenvironment to alleviate tumor hypoxia. Manganese dioxide has also been used to quench fluorescent carbon dots in fluorescent probes. Based on the oxidation ability and catalytic activity of MnO2, MnO2 nanosheets are widely used to build biosensors. New research shows that manganese dioxide nanomaterials also have great potential in gene therapy and nuclear magnetic imaging. read less NOT USED (high confidence) X. Liu, X. Wen, and R. Hoffmann, “Surface Activation of Transition Metal Nanoparticles for Heterogeneous Catalysis: What We Can Learn from Molecular Dynamics,” ACS Catalysis. 2018. link Times cited: 43 Abstract: Many heterogeneous reactions catalyzed by nanoparticles occu… read moreAbstract: Many heterogeneous reactions catalyzed by nanoparticles occur at relatively high temperatures, which may modulate the surface morphology of nanoparticles during reaction. Inspired by the discovery of dynamic formation of active sites on gold nanoparticles, we explore theoretically the nature of the highly mobile atoms on the surface of nanoparticles of various sizes for 11 transition metals. Using molecular dynamics simulations, on a 3 nm Fe nanoparticle as an example, the effect of surface premelting and overall melting on the structure and physical properties of the nanoparticles is analyzed. When the nanoparticle is heated up, the atoms in the outer shell appear amorphous already at 900 K. Surface premelting is reached at 1050 K, with more than three liquid atoms, based on the Lindemann criterion. The activated atoms may transfer their extra kinetic energy to the rest of the nanoparticle and activate other atoms. The dynamic studies indicate that the number of highly mobile atoms on the surface increas... read less NOT USED (high confidence) F. Moulai, N. Cherchour, B. Messaoudi, and L. Zerroual, “Electrosynthesis and characterization of nanostructured MnO2 deposited on stainless steel electrode: a comparative study with commercial EMD,” Ionics. 2017. link Times cited: 11 NOT USED (high confidence) A. Barnard, “Challenges in modelling nanoparticles for drug delivery,” Journal of Physics: Condensed Matter. 2016. link Times cited: 22 Abstract: Although there have been significant advances in the fields … read moreAbstract: Although there have been significant advances in the fields of theoretical condensed matter and computational physics, when confronted with the complexity and diversity of nanoparticles available in conventional laboratories a number of modeling challenges remain. These challenges are generally shared among application domains, but the impacts of the limitations and approximations we make to overcome them (or circumvent them) can be more significant one area than another. In the case of nanoparticles for drug delivery applications some immediate challenges include the incompatibility of length-scales, our ability to model weak interactions and solvation, the complexity of the thermochemical environment surrounding the nanoparticles, and the role of polydispersivity in determining properties and performance. Some of these challenges can be met with existing technologies, others with emerging technologies including the data-driven sciences; some others require new methods to be developed. In this article we will briefly review some simple methods and techniques that can be applied to these (and other) challenges, and demonstrate some results using nanodiamond-based drug delivery platforms as an exemplar. read less NOT USED (high confidence) L. Li, X. Guo, F. Hao, X. Zhang, and J. Chen, “Solid-state grinding/low-temperature calcining synthesis of carbon coated MnO2 nanorods and their electrochemical capacitive property,” New Journal of Chemistry. 2015. link Times cited: 11 Abstract: Taking malic acid as the carbon source, carbon coated-mangan… read moreAbstract: Taking malic acid as the carbon source, carbon coated-manganese dioxide (MnO2) nanorods (MnO2@C NRs) were prepared using a solid-state grinding/low-temperature calcining synthesis method. The morphology, structure and electrochemical capacitive property of MnO2@C NRs were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, surface area and pore size analysis and electrochemical methods. The results demonstrated that the thickness of the carbon layer on the surface of the MnO2 NRs is about 3 nm and the MnO2@C NRs have an improved capacitive performance and excellent long-term cycling stability. This method provides an easy route of synthesis with energy savings, cost effectiveness, environmental friendliness and large-scale production ability in the synthesis of carbon coated metal oxide nanomaterials. read less NOT USED (high confidence) T. Sayle, L. W. L. Sayle, and D. Sayle, “Liquid crystal seed nucleates liquid-solid phase change in ceria nanoparticles.,” Physical chemistry chemical physics : PCCP. 2015. link Times cited: 5 Abstract: Molecular dynamics (MD) simulation was used to explore the l… read moreAbstract: Molecular dynamics (MD) simulation was used to explore the liquid-solid (crystal) phase change of a ceria nanoparticle. The simulations reveal that the crystalline seed, which spontaneously evolves and nucleates crystallisation, is a liquid rather than a solid. Evidence supporting this concept includes: (a) only 3% of the total latent heat of solidification had been liberated after 25% of the nanoparticle had (visibly) crystallised. (b) Cerium ions, comprising the (liquid) crystal seed had the same mobility as cerium ions comprising the amorphous regions. (c) Cerium ion mobility only started to reduce (indicative of solidification) after 25% of the nanoparticle had crystallised. (d) Calculated radial distribution functions (RDF) revealed no long-range structure when 25% of the nanoparticle had (visibly) crystallised. We present evidence that the concept of a liquid crystal seed is more general phenomenon rather than applicable only to nanoceria. read less NOT USED (high confidence) J. Dawson and I. Tanaka, “Oxygen vacancy formation and reduction properties of β-MnO2 grain boundaries and the potential for high electrochemical performance.,” ACS applied materials & interfaces. 2014. link Times cited: 36 Abstract: In recent years, the nanostructuring of rutile (β-)MnO2 has … read moreAbstract: In recent years, the nanostructuring of rutile (β-)MnO2 has been shown to vastly improve its properties and performance in a number of technological applications. The contrast between the strong electrochemical properties of the nanostructured material and the bulk material that shows limited Li intercalation and electrochemical capacitance is not yet fully understood. In this work, we investigate the structure, stability and catalytic properties of four tilt grain boundaries in β-MnO2 using interatomic potential methods. By considering the γ-surfaces of each of the grain boundaries, we are able to find the lowest energy configurations for each grain boundary structure. For each grain boundary, we observe a significant decrease in the oxygen vacancy energies in and around the grain boundaries compared to bulk β-MnO2 and also the bulk-like structures in the grain boundary cells. The reduction of Mn(4+) to Mn(3+) is also considered and again is shown to be preferable at the boundaries. These energies suggest a potentially higher catalytic activity at the grain boundaries of β-MnO2. The results are also placed into context with recent calculations of β-MnO2 surfaces to produce a more detailed understanding into this important phenomenon. read less NOT USED (high confidence) D. Tompsett, S. C. Parker, and M. S. Islam, “Surface properties of α-MnO2: relevance to catalytic and supercapacitor behaviour,” Journal of Materials Chemistry. 2014. link Times cited: 91 Abstract: Hollandite (α-)MnO2 gives superior performance compared to o… read moreAbstract: Hollandite (α-)MnO2 gives superior performance compared to other MnO2 polymorphs in surface sensitive applications in supercapacitors and catalysis. However, a thorough understanding of its atomic-scale surface properties is lacking, which we address here using density functional theory (DFT). A Wulff construction based upon relaxed surface energies demonstrates that the equilibrium morphology expresses the low index (100), (110) and (111) surfaces as well as the high index (211) and (112) surfaces. The predicted morphology exhibits clear elongation along the c-axis which is consistent with the large number of nanorod type structures that are obtainable experimentally. The surface structures expressed in the morphology are discussed in detail and it is found that α-MnO2 gives rise to larger surface relaxations than are observed for the less open rutile structured MnO2. Enhanced magnetic moments at surface sites are rationalised by a crystal field argument. Experimental studies consistently find that α-MnO2 has higher catalytic activity than other polymorphs of MnO2. In this work, calculated formation energies for oxygen vacancy defects at the expressed surfaces are demonstrably lower, by ∼1 eV, than for rutile MnO2 surfaces [Tompsett et al., JACS, 2014, 136, 1418]. The lowest vacancy formation energy occurs at the (112) surface, which despite its relative high Miller index constitutes 17% of the surface area of the calculated morphology. This may play a key role in the favourable catalytic performance observed for α-MnO2 in a broad range of applications. read less NOT USED (high confidence) D. Tompsett, S. C. Parker, and M. Islam, “Rutile (β-)MnO2 surfaces and vacancy formation for high electrochemical and catalytic performance.,” Journal of the American Chemical Society. 2014. link Times cited: 176 Abstract: MnO2 is a technologically important material for energy stor… read moreAbstract: MnO2 is a technologically important material for energy storage and catalysis. Recent investigations have demonstrated the success of nanostructuring for improving the performance of rutile MnO2 in Li-ion batteries and supercapacitors and as a catalyst. Motivated by this we have investigated the stability and electronic structure of rutile (β-)MnO2 surfaces using density functional theory. A Wulff construction from relaxed surface energies indicates a rod-like equilibrium morphology that is elongated along the c-axis, and is consistent with the large number of nanowire-type structures that are obtainable experimentally. The (110) surface dominates the crystallite surface area. Moreover, higher index surfaces than considered in previous work, for instance the (211) and (311) surfaces, are also expressed to cap the rod-like morphology. Broken coordinations at the surface result in enhanced magnetic moments at Mn sites that may play a role in catalytic activity. The calculated formation energies of oxygen vacancy defects and Mn reduction at key surfaces indicate facile formation at surfaces expressed in the equilibrium morphology. The formation energies are considerably lower than for comparable structures such as rutile TiO2 and are likely to be important to the high catalytic activity of rutile MnO2. read less NOT USED (high confidence) A. M. Toufiq, F. Wang, Q.-ul-ain Javed, and Y. Li, “Influence of SiO2 on the structure-controlled synthesis and magnetic properties of prismatic MnO2 nanorods,” Nanotechnology. 2013. link Times cited: 21 Abstract: Silicon dioxide-doped tetragonal MnO2 single crystalline pri… read moreAbstract: Silicon dioxide-doped tetragonal MnO2 single crystalline prismatic nanorods have been successfully synthesized through a facile hydrothermal route at a temperature of 250 ° C with a reaction time as quick as 5 h. The synthesized MnO2 prismatic nanorods were characterized by x-ray diffraction, field emission scanning electron microscopy, energy dispersive x-ray analysis, transmission electron microscopy, high resolution transmission electron microscopy with selected area electron diffraction and Raman spectroscopy. Experimental results show that single crystalline tetragonal MnO2 nanorods have been successfully synthesized at all doping concentrations and that nanorods with a prismatic surface morphology have been obtained at 20 mass% of SiO2. The diameter of as-prepared MnO2 nanorods increases from 125 to 250 nm on increasing the dopant concentration. X-ray photoelectron spectroscopy analysis confirms the presence of valence Si (2p) of SiO2 in the as-prepared MnO2 nanostructures. The intensity of Raman modes clearly increases with increasing doping concentration, indicating an improvement in the structural aspects of the MnO2 nanorods. The magnetic properties of the products have been evaluated using a vibrating sample magnetometer, revealing that the as-prepared MnO2 nanorods exhibit weak ferromagnetic behavior at room temperature. The Néel temperature of the as-obtained products is calculated as 97 K. On the basis of the structural information, a growth mechanism is proposed for the formation of prismatic-like 1D MnO2 nanorods. read less NOT USED (high confidence) R. Subbaraman, S. Sankaranarayanan, and S. Ramanathan, “Electric field assisted annealing effects on microstructure and ionic conductivity in ceria/YSZ oxide heterostructures,” Philosophical Magazine. 2013. link Times cited: 2 Abstract: The effect of electric field assisted annealing on the micro… read moreAbstract: The effect of electric field assisted annealing on the microstructure, composition and ionic conductivity properties in CeO2/YSZ oxide heterostructures have been investigated using molecular dynamics simulations. Amorphization–recrystallization steps were performed with and without external electric field of strength 10 MV/cm along three different orientations: in-plane (YZ), normal (X) and 45° resultant (XY) with respect to the oxide heterointerfaces. The microstructural and compositional differences at the interfaces and in the interior of the oxide heterolayers were evaluated and were found to show a clear correlation with the orientations of the applied field. In particular, the XY configuration displayed a compressive lattice strain of ∼9% along with a reduced oxygen vacancy concentration when compared to the others. Ionic density profiles suggest pronounced segregation (∼60% higher compared to the average value in the interior) of yttrium ions closer to the YSZ/CeO2 interface for the XY configuration. Other configurations exhibit minimal to no such variations. These microstructural differences are found to affect the number of mobile charge carriers and the activation barriers associated with ionic migration through the oxide lattice and consequently, influence the ionic conductivity. read less NOT USED (high confidence) J. Anwar and D. Zahn, “Atomistisches Verständnis der Keimbildung und des Kristallwachstums durch molekulare Simulationen,” Angewandte Chemie. 2011. link Times cited: 16 Abstract: Die Modellierung von Keimbildungsprozessen durch molekulare … read moreAbstract: Die Modellierung von Keimbildungsprozessen durch molekulare Simulation ermoglicht nicht nur die Berechnung kinetischer und thermodynamischer Eigenschaften, sondern bietet zugleich mechanistische Einblicke auf atomarer Ebene. Die vielfaltigen Moglichkeiten, Experimente durch Modellsimulationen zu erganzen, sind jedoch mit der Uberwindung einer Reihe von technischen Schwierigkeiten verbunden. Keimbildungsprozesse sind seltene Ereignisse, die direkten Brute-Force-Molekulardynamiksimulationen nur in Ausnahmefallen zuganglich sind. Erst durch Fortschritte bei der Uberbruckung von Zeit- und Langenskalen konnten kurzlich entwickelte Ansatze auch solche Simulationen ermoglichen, die lange Zeit als undurchfuhrbar galten. Dabei konnen einerseits generische Modelle zur Erarbeitung eines allgemeinen Verstandnisses genutzt werden. Zum anderen sind aber auch detaillierte Einblicke in realitatsnahe Systeme moglich, sofern die Kristallbildungsprozesse in handhabbare Module unterteilt werden. So konnen die Assoziation einzelner Ionen in der Losung, die Bildung von geordneten Motiven, Reifungsreaktionen, Keimbildung und postkritisches Wachstum von Nanokristallen auf molekularer Ebene untersucht werden. Durch die Analyse des Wechselspiels mit additiven Molekulen lassen sich zudem Einblicke in funktionalisierte Nanopartikel und Kompositmaterialien gewinnen. read less NOT USED (high confidence) S. Sankaranarayanan and S. Ramanathan, “Interface proximity effects on ionic conductivity in nanoscale oxide-ion conducting yttria stabilized zirconia: an atomistic simulation study.,” The Journal of chemical physics. 2011. link Times cited: 27 Abstract: We present an atomistic simulation study on the size depende… read moreAbstract: We present an atomistic simulation study on the size dependence of dopant distribution and the influence of nanoscale film thickness on carrier transport properties of the model oxide-ion conductor yttria stabilized zirconia (YSZ). Simulated amorphization and recrystallization approach was utilized to generate YSZ films with varying thicknesses (3-9 nm) on insulating MgO substrates. The atomic trajectories generated in the molecular dynamics simulations are used to study the structural evolution of the YSZ thin films and correlate the resulting microstructure with ionic transport properties at the nanoscale. The interfacial conductivity increases by 2 orders of magnitude as the YSZ film size decreases from 9 to 3 nm owing to a decrease in activation energy barrier from 0.54 to 0.35 eV in the 1200-2000 K temperature range. Analysis of dopant distribution indicates surface enrichment, the extent of which depends on the film thickness. The mechanisms of oxygen conductivity for the various film thicknesses at the nanoscale are discussed in detail and comparisons with experimental and other modeling studies are presented where possible. The study offers insights into mesoscopic ion conduction mechanisms in low-dimensional solid oxide electrolytes. read less NOT USED (high confidence) T. Sayle and D. Sayle, “Elastic deformation in ceria nanorods via a fluorite-to-rutile phase transition.,” ACS nano. 2010. link Times cited: 19 Abstract: Atomistic simulations reveal that ceria nanorods, under unia… read moreAbstract: Atomistic simulations reveal that ceria nanorods, under uniaxial tension, can accommodate over 6% elastic deformation. Moreover, a reversible fluorite-to-rutile phase change occurs above 6% strain for a ceria nanorod that extends along [110]. We also observe that during unloading the stress increases with decreasing strain as the rutile reverts back to fluorite. Ceria nanorods may find possible application as vehicles for elastic energy storage. read less NOT USED (high confidence) M. A. Lovette, A. Browning, D. W. Griffin, J. P. Sizemore, R. C. Snyder, and M. Doherty, “Crystal Shape Engineering,” Industrial & Engineering Chemistry Research. 2008. link Times cited: 272 Abstract: In an industrial crystallization process, crystal shape stro… read moreAbstract: In an industrial crystallization process, crystal shape strongly influences end-product quality and functionality, as well as downstream processing. In addition, nucleation events, solvent effects, and polymorph selection play critical roles in both the design and operation of a crystallization plant and the patentability of the product and process. Therefore, investigation of these issues, with respect to a priori prediction, is (and will continue to be) an important avenue of research. In this review, we discuss the state-of-the-art in modeling crystallization processes over a range of length scales relevant to nucleation through process design. We also identify opportunities for continued research and specific areas where significant advancements are needed. read less NOT USED (high confidence) D. Cooke and J. Elliott, “Atomistic simulations of calcite nanoparticles and their interaction with water.,” The Journal of chemical physics. 2007. link Times cited: 42 Abstract: Molecular dynamics (MD) simulations have been used to study … read moreAbstract: Molecular dynamics (MD) simulations have been used to study the stability of calcite nanoparticles ranging in size from 18 to 324 f.u., both in vacuo and in the presence of explicit water molecules. In vacuo, the smallest particles become highly disordered during the MD simulation due to rotation and translation of the undercoordinated CO(3) (2-) anions at the edges of the particles. As the nanoparticle size increases, the influence of the fully coordinated bulk ions begins to dominate and long-range order is seen both in the Ca-C pair distribution functions and in the degree of rotational order of the CO(3) (2-) anions. However, when explicit water is added to the system, the molecules in the first hydration layer complete the coordination shell of the surface ions, preserving structural order even in the smallest of the nanoparticles. Close to particle surface, the structure of the water itself shows features similar to those seen close to planar periodic (1014) surfaces, although the molecules are far less tightly bound. read less NOT USED (high confidence) T. Sayle, S. C. Parker, and D. Sayle, “Ionic conductivity in nano-scale CeO2/YSZ heterolayers,” Journal of Materials Chemistry. 2006. link Times cited: 42 Abstract: CeO2 based materials are promising candidates as solid oxide… read moreAbstract: CeO2 based materials are promising candidates as solid oxide electrolytes within fuel cell systems. In this capacity, the oxygen anion conductivity is pivotal. Sata et al. [Nature, 2000, 408, 946–949] demonstrated the ability to ‘fine tune’ conductivities in BaF2 and CaF2 by generating BaF2/CaF2 heterolayers with different nanoscale film thicknesses. The resulting fluoride ion conductivities were found to be orders of magnitude higher compared with the component BaF2 and CaF2 materials. Similarly, it may be possible to fabricate CeO2 thin films with tuneable conductivities. In this study, we explore this possibility using atomistic simulation. In particular, simulated amorphisation and recrystallisation was used to generate an atomistic model for a CeO2/YSZ (yttrium stabilised zirconia) heterolayered system and, using this model, the ionic diffusivity, conductivity and associated activation energy barriers were calculated. However, in contrast to the BaF2/CaF2 system, the heterolayered CeO2/YSZ system did not exhibit exemplary transport properties compared with the parent materials. This study describes a framework simulation procedure, which can be used in partnership with experiment, to explore a variety of microstructural features that may facilitate an increase in the ionic conductivity of heterolayered systems. read less NOT USED (high confidence) J. C. M. Madrid, J. Matsuda, K. Leonard, H. Matsumoto, and K. Ghuman, “Molecular Dynamics Study of Oxygen-ion Diffusion in Yttria-Stabilized Zirconia Grain Boundaries,” Journal of Materials Chemistry A. 2022. link Times cited: 3 Abstract: This work focuses on understanding the oxygen-ion transport … read moreAbstract: This work focuses on understanding the oxygen-ion transport through the mixed Grain Boundaries (GBs) present in Yttria-stabilized zirconia (YSZ), a common solid oxide fuel cells (SOFCs) electrolyte. The mixed GBs,... read less |