# Modified Embedded Atom Method (MEAM) potential This directory contains the modified embedded atom method (MEAM) potential model driver [[1,2,3,4,5,6,7,8](#references)]. ## MEAM model driver This KIM model driver is written in C++ and implements three styles of modified embedded atom method (MEAM) potentials: - ['meam'](#meam-style) - ['meam/spline'](#meamspline-style) - ['meam/sw/spline'](#meamswspline-style) The style of the potential is automatically detected based on the input files to the driver. The input files are ASCII text files formatted to be consistent with the other MD codes that implement MEAM potentials, such as LAMMPS, serial DYNAMO code, and Warp. This driver has a design to mimic and reproduce the behavior of the [LAMMPS](https://lammps.org) ['meam'](https://docs.lammps.org/pair_meam.html), ['meam/spline'](https://docs.lammps.org/pair_meam_spline.html), and ['meam/sw/spline'](https://docs.lammps.org/pair_meam_sw_spline.html) pair styles.\ We adapted the LAMMPS format from the [LAMMPS documentation](https://docs.lammps.org/) as of `Oct 15, 2020` (note that, at that time, the `meam` pair style was still referred to as `meam/c`). For any of the three styles mentioned above, the driver expects an element file. Depending on the specific potential style, other files may be required/supplied and will be outlined in their respective sections below. ### Element file format The element file contains a unique list of chemical element names separated by spaces: ```bash Elem1 Elem2 Elem3 ... ``` For example, for an Si and C alloy system the element file may look like this: ```bash Si C ``` For an alloy system containing Al, Si, Mg, Cu, and Fe, it could look like this: ```bash Al Si Mg Cu Fe ``` **NOTE:** There is no limit on the maximum number of elements in the element file. **NOTE:** The order in which elements are listed in the element file defines the integral indices used to identify each element in the [MEAM parameter file](#meam-parameter-file-format) (if you choose to specify one). Therefore, care must be taken to ensure that the indices used to assign parameter values in the MEAM parameter file are consistent with the order of the elements in the element file. (See details [below](#meam-parameter-file-format) on the syntax for settings in the 'meam' parameter file.) ## MEAM style In the 'meam' style, the driver computes pairwise interactions for a variety of materials using modified embedded atom method (MEAM) potentials [[1,2,3,4,5,6,7](#references)]. Conceptually, it is an extension to the original EAM potentials that adds angular forces. It is thus suitable for modeling metals and alloys with `fcc`, `bcc`, `hcp` and `diamond` cubic structures, as well as covalently bonded materials like silicon and carbon. In the MEAM formulation, the total energy Ei of an atom I is given by: ```tex E_i = U_\alpha (\Bar{\rho}_i) + \frac{1}{2}\sum\limits_{j \ne i} \phi_{\alpha \beta}(r_{ij}), ``` where `U` is the embedding energy which is a function of the atomic electron density `rho bar`, and `phi` is a pair potential interaction. The pair interaction is summed over all neighbors J of atom I within the cutoff distance. As with EAM, the multi-body nature of the MEAM potential is a result of the embedding energy term. Details of the computation of the embedding and pair energies, as implemented in this model driver, are given in [[9](#references)] and references therein. The various parameters in the MEAM formulas are listed in two files. 1) The MEAM library file, usually `library.meam`. 2) The MEAM parameter file (alloy parameter file). The name usually contains the elements' names and ends in the `.meam` extension. For example, for an alloy containing Si and C, the `SiC.meam` file (alloy parameter file) contains the specific parameter settings. ### MEAM library file format This file has generic MEAM settings for a variety of elements. The MEAM library file is an input file by some MD codes (e.g., LAMMPS, serial DYNAMO code, and Warp). Aside from blank and comment lines (which start with #), which can appear anywhere, its format is a series of entries, each of which has 19 parameters and can span multiple lines [[11](#references)]. ```txt elt, lat, z, ielement, atwt, alpha, b0, b1, b2, b3, alat, esub, asub, t0, t1, t2, t3, rozero, ibar ``` The `elt` and `lat` parameters are text strings, such as `elt = Si` or `elt = Cu` and `lat = bcc, dia, ... or fcc`. Because Fortran MD codes use the library file, these strings may include single quotes [[11](#references)]. To choose and identify the library file's proper settings, we use the value of the `elt` string. Since there can be multiple entries in the library file with the same `elt` value, we follow the LAMMPS code [[10](#references)], reading the first matching entry and ignoring the rest. In the MEAM library file, the parameters `lat, z, ielement, atwt, alat, esub, asub` correspond to single-element potential parameters. The meaning of these paramters is as follows: ```txt lat = lattice structure of reference configuration z = number of nearest neighbors in the reference structure ielement = atomic number atwt = atomic weight alat = lattice constant of reference structure esub = energy per atom (eV) in the reference structure at equilibrium asub = "A" parameter for the MEAM (see e.g., [1,2]) ``` The `alpha, b0, b1, b2, b3, t0, t1, t2, t3` parameters correspond to the literature's standard MEAM parameters [[1,2](#references)] (the `b*` parameters are the standard beta parameters). Note that only parameters normalized to `t0 = 1.0` are supported. The `rozero` parameter is an element-dependent density scaling that weights the reference background density (see, e.g., equation 4.5 in [[9](#references)]) and is typically 1.0 for single-element systems. The `ibar` parameter selects the form of the function `G(Gamma)` used to compute the electron density. Different values of the `ibar` parameter correspond to the following forms: ```txt 0 => G = sqrt(1+Gamma) 1 => G = exp(Gamma/2) 2 => not implemented 3 => G = 2/(1+exp(-Gamma)) 4 => G = sqrt(1+Gamma) -5 => G = +-sqrt(abs(1+Gamma)) ``` An example MEAM library file for an SiC alloy system is shown below: ```bash # DATE: 2012-06-29 UNITS: metal DATE: 2007-06-11 # CONTRIBUTOR: Greg Wagner, gjwagne@sandia.gov # CITATION: Baskes, Phys Rev B, 46, 2727-2742 (1992) # meam data from vax files fcc,bcc,dia 11/4/92 # elt lat z ielement atwt # alpha b0 b1 b2 b3 alat esub asub # t0 t1 t2 t3 rozero ibar 'Si' 'dia' 4. 14 28.086 4.87 4.8 4.8 4.8 4.8 5.431 4.63 1. 1.0 3.30 5.105 -0.80 1. 1 'C' 'dia' 4. 6 12.0111 4.38 4.10 4.200 5.00 3.00 3.567 7.37 1.000 1.0 5.0 9.34 -1.00 2.25 1 ``` **NOTE:** There is no limit on the maximum number of elements that can be read from the MEAM library file. ### MEAM parameter file format The MEAM parameter file is an optional file containing settings that override or complement the library file settings. The format is the same as is read by other Fortran MD codes. Aside from blank and comment lines (start with `#`), which can appear anywhere, each line has one of the following forms: ```txt keyword = value keyword(I) = value keyword(I,J) = value keyword(I,J,K) = value ``` The driver also ignores anything after a trailing comment within a line (starting with `#`). The indices I, J, K correspond to the elements listed in the [MEAM element file](#element-file-format) in the order in which they appear. These indices start from 1 to be compatible with LAMMPS and the other Fortran MD codes. For example, if one were modeling an alloy containing Al, Si, Mg, Cu, and Fe, and used a MEAM element file containing the following: ```bash Al Si Mg Cu Fe ``` then an index of 1 would refer to Al, an index of 2 to Si, an index of 3 to Mg, an index of 4 to Cu, and an index of 5 to Fe. The recognized keywords for the parameter file are as follows: ```txt rc = cutoff radius for cutoff function. (default = 4.0) delr = length of smoothing distance for cutoff function. (default = 0.1) rho0(I) = relative density for element I Ec(I,J) = cohesive energy of reference structure for I-J mixture delta(I,J) = heat of formation for I-J alloy. If Ec_IJ is input as zero, then driver sets Ec_IJ = (Ec_II + Ec_JJ)/2 - delta_IJ alpha(I,J) = alpha parameter for pair potential between I and J (can be computed from bulk modulus of reference structure re(I,J) = equilibrium distance between I and J in the reference structure Cmax(I,J,K) = Cmax screening parameter when I-J pair is screened by K (I<=J); default = 2.8 Cmin(I,J,K) = Cmin screening parameter when I-J pair is screened by K (I<=J); default = 2.0 lattce(I,J) = lattice structure of I-J reference structure: fcc = face centered cubic bcc = body centered cubic hcp = hexagonal close-packed dim = dimer dia = diamond (interlaced fcc for alloy) dia3 = diamond structure with primary 1NN and secondary 3NN interaction b1 = rock salt (NaCl structure) c11 = MoSi2 structure l12 = Cu3Au structure (lower case L, followed by 12) b2 = CsCl structure (interpenetrating simple cubic) ch4 = methane-like structure, only for binary system lin = linear structure (180 degree angle) zig = zigzag structure with a uniform angle tri = H2O-like structure that has an angle nn2(I,J) = turn on second-nearest neighbor MEAM formulation for I-J pair (see for example []()). (default = 0) 0 = second-nearest neighbor formulation off 1 = second-nearest neighbor formulation on attrac(I,J) = additional cubic attraction term in Rose energy I-J pair potential (default = 0) repuls(I,J) = additional cubic repulsive term in Rose energy I-J pair potential (default = 0) zbl(I,J) = blend the MEAM I-J pair potential with the ZBL potential for small atom separations (ZBL) (default = 1) theta(I,J) = angle between three atoms in line, zigzag, and trimer reference structures in degrees (default = 180) gsmooth_factor = factor determining the length of the G-function smoothing region. (default = 99.0) Only significant for ibar=0 or ibar=4. 99.0 = short smoothing region, sharp step 0.5 = long smoothing region, smooth step augt1 = integer flag for whether to augment t1 parameter by 3/5*t3 to account for old vs. new meam formulations, (default = 1) 0 = don't augment t1 1 = augment t1 ialloy = integer flag to use alternative averaging rule for t parameters, for comparison with the DYNAMO MEAM code (default = 0) 0 = standard averaging (matches ialloy=0 in DYNAMO) 1 = alternative averaging (matches ialloy=1 in DYNAMO) 2 = no averaging of t (use single-element values) mixture_ref_t = integer flag to use mixture average of t to compute the background reference density for alloys, instead of the single-element values (see description and warning elsewhere in this doc page) (default = 0) 0 = do not use mixture averaging for t in the reference density 1 = use mixture averaging for t in the reference density erose_form = integer value to select the form of the Rose energy function (see description below) (default = 0). emb_lin_neg = integer value to select embedding function for negative densities (default = 0) 0 = F(rho)=0 1 = F(rho) = -asub*esub*rho (linear in rho, matches DYNAMO) bkgd_dyn = integer value to select background density formula (default = 0) 0 = rho_bkgd = rho_ref_meam(a) (as in the reference structure) 1 = rho_bkgd = rho0_meam(a)*Z_meam(a) (matches DYNAMO) fcut_form = integer value to select the form of the MEAM cut-off function (see description below) (default = 0). ``` `Rc, delr, re` are in distance units (`Angstroms` in the case of metal units). `Ec` and `delta` are in the energy units (`eV` in the case of metal units). Each keyword represents a quantity which is either a scalar, vector, 2d array, or 3d array and must be specified with the correct corresponding array syntax. The indices I,J,K each run from 1 to N where N is the number of MEAM elements being used. Thus, these lines, ```txt rho0(4) = 3.0 alpha(1,5) = 4.2 ``` set `rho0` for the fourth element to the value 3.0 and set the `alpha` for the cross-species interaction between elements 1 and 5 to 4.2. The `augt1` parameter is related to modifications in the MEAM formulation of the partial electron density function. The augmentation is the default option. But when the parameter values are fit using the modified density function, `augt1` is 0. The `mixture_ref_t` parameter is related to the background reference density computation. Setting `mixture_ref_t=1` causes the driver to use an alloy mixture averaged value of t to compute the background reference density. The proper way to calculate the background reference density is to use the single-element values of the t parameters. **NOTE:** One should avoid using `mixture_ref_t=1` whenever possible [[11](#references)]. Using `mixture_ref_t=1` will give incorrect results for the second-neighbor MEAM, and it is non-standard for the first-neighbor MEAM. The parameters `attrac` and `repuls,` along with the integer selection parameter `erose_form,` can be used to modify the Rose energy function used to compute the pair potential. This function gives the energy of the reference state as a function of interatomic spacing. The form of this function is: ```tex a^* = \alpha (\frac{r}{r_e} - 1) form=0 E=\left\{\begin{matrix} -E_c\left(1+a^*+ {a_\text{repuls}}~ \frac{{a^*}^3}{r/re} \right)exp(-a^*) & a^* < 0\\ -E_c\left(1+a^*+ {a_\text{attrac}}~ \frac{{a^*}^3}{r/re} \right)exp(-a^*) & a^* \geqslant 0 \end{matrix}\right. form=1 E=-E_c\left(1+a^*+ \left(-{a_\text{attrac}}~+ \frac{{a_\text{repuls}}}{r}\right){a^*}^3 \right)exp(-a^*) form=2 E=\left\{\begin{matrix} -E_c\left(1+a^*+ {a_\text{repuls}}~ {a^*}^3 \right)exp(-a^*) & a^* < 0\\ -E_c\left(1+a^*+ {a_\text{attrac}}~ {a^*}^3 \right)exp(-a^*) & a^* \geqslant 0 \end{matrix}\right. ``` **NOTE:** `fcut_form` is an addition to the current MEAM model driver, and the parameter is not valid when used in LAMMPS. The cutoff function describes the smooth, gradually decreasing distance effect. The MEAM cut-off function (fc) is defined, ```tex form=0 f_c(x)=\left\{\begin{matrix} 1 & x \geqslant 0\\ \left[1 - (1 - x)^4 \right]^2 & 0 < x < 1\\ 0 & x \leqslant 0\\ \end{matrix}\right. form=1 f_c(x)=\left\{\begin{matrix} 1 & x \geqslant 0\\ \left[1 - (1 - x)^6 \right]^2 & 0 < x < 1\\ 0 & x \leqslant 0\\ \end{matrix}\right. ``` The cut-off function has the `(1-x)` term to the fourth power `form=0`, however, in some cases the power is changed to sixth `form=1` [[18](#references)]. For example, below is an example MEAM parameter file for a SiC alloy system: ```bash # DATE: 2007-06-11 UNITS: metal CONTRIBUTOR: Greg Wagner, gjwagne@sandia.gov CITATION: Unknown lattce(1,2) = 'dia' Ec(1,2) = 6.4325 alpha(1,2) = 4.37 re(1,2) = 1.8878 rho0(2) = 2.25 rc = 4.0 delr = 0.1 Cmax(1,2,1) = 4.0 Cmax(1,2,2) = 4.0 Cmax(2,2,1) = 4.0 Cmax(1,1,2) = 4.0 ``` ### MEAM style example As an example, a KIM Portable Model (PM) for pure `Al` systems that uses this model driver with the `meam` style might contain the following three input files: ```bash elems.meam library.meam Al.meam ``` where `elems.meam` element file would contain ```bash # list of elements # Elem1, Elem2 Al ``` the `library.meam` library file might consist of ```bash # References: # elt lat z ielement atwt # alpha b0 b1 b2 b3 alat esub asub # t0 t1 t2 t3 rozero ibar # 'Al' 'fcc' 12. 13 26.9815 4.68604 1.56205 5.39270 5.29601 -1.00047 4.05000 3.35999 1.06859 1.0 -1.54917 -1.28508 10.01041 1.0 0 ``` and the `Al.meam` MEAM parameter file could contain ```bash re(1,1) = 2.86378 attrac(1,1) = 0.39558 repuls(1,1) = 0.09806 Cmin(1,1,1) = 1.00769 Cmax(1,1,1) = 2.31407 rc = 5.0 delr = 0.1 augt1 = 1 ``` ## MEAM/SPLINE style The `meam/spline` style supported by this model driver stems from code primarily intended for modeling metals [[8,16](#references)]. This driver supports both a single species (also called "old-style" MEAM) and multi-component species (also called "new-style" MEAM). In this style, the atomic electron density is, ```tex \Bar{\rho}_i=\sum\limits_{j \ne i}\rho_j(r_{ij}) + \sum\limits_{\substack{j < k, \\ j \ne i}} f_j(r_{ij}) f_k(r_{ik}) g_{jk}{\left(\cos(\theta_{jik})\right)}, ``` where `rho` is the density, and `theta` is the angle between atoms. The five functions `phi`, `U`, `rho`, `f`, and `g` depend on the atoms in the interaction. Specifically, if there are N species, then there are N different functions `U`, `rho`, and `f`, and there are N(N+1)/2 functions `phi` and `g`. Each of these functions is tabulated as a cubic spline. While the list of elements is in the element file, the potential file indicates the cutoffs and the coefficients for these spline functions. The MEAM potential file name usually contains the elements' names and ends in the `.meam.spline` extension. For example, for an SiC alloy system, the `SiC.meam.spline` file contains all of the specific parameter settings. ### MEAM potential file format In the new-style potential file, the second line begins with the string `meam/spline` followed by the number of unique species and their names. The names of the elements and the order in which they appear should match the MEAM element file. ### MEAM/SPLINE style example As an example, a KIM Portable Model (PM) for pure `Si` systems that uses this model driver with the `meam/spline` style might contain the following two input files: ```bash elems.meam Si.meam.spline ``` where `elems.meam` element file would contain ```bash # list of elements # Elem1, Elem2 Si ``` and the `Si.meam.spline` potential file could contain ```bash Spline-based MEAM potential for Si. Reference: T. J. Lenosky, B. Sadigh, E. Alonso, V. V. Bulatov, T. D. de la Rubia, J. Kim, A. F. Voter, and J. D. Kress, Modell. Simul. Mater. Sci. Eng. 8, 825 (2000) 10 -4.266966781858503300e+01 0.000000000000000000e+00 1 0 1 0 1.500000000000000000e+00 6.929943430771341000e+00 1.653321602557917600e+02 1.833333333333333300e+00 -4.399503747408950400e-01 3.941543472528634600e+01 2.166666666666666500e+00 -1.701233725061446700e+00 6.871065423413908100e+00 2.500000000000000000e+00 -1.624732919215791800e+00 5.340648014033163800e+00 2.833333333333333000e+00 -9.969641728342462100e-01 1.534811309391571000e+00 3.166666666666667000e+00 -2.739141845072665100e-01 -6.334706186546093900e+00 3.500000000000000000e+00 -2.499156963774082700e-02 -1.798864729909626500e+00 3.833333333333333500e+00 -1.784331481529976400e-02 4.743496636420091500e-01 4.166666666666666100e+00 -9.612303290166881000e-03 -4.006506271304824400e-02 4.500000000000000000e+00 0.000000000000000000e+00 -2.394996574779807200e-01 11 -1.000000000000000000e+00 0.000000000000000000e+00 1 0 0 0 1.500000000000000000e+00 1.374674212682983900e-01 -3.227795813279568500e+00 1.700000000000000000e+00 -1.483141815327918000e-01 -6.411648793604404900e+00 1.899999999999999900e+00 -5.597204896096039700e-01 1.003068519633888300e+01 2.100000000000000100e+00 -7.310964379372824100e-01 2.293461970618954700e+00 2.299999999999999800e+00 -7.628287071954063000e-01 1.742018781618444500e+00 2.500000000000000000e+00 -7.291769685066557000e-01 5.460640949384478700e-01 2.700000000000000200e+00 -6.662022220044453400e-01 4.721760106467195500e-01 2.899999999999999900e+00 -5.732830582550895200e-01 2.056894449546524200e+00 3.100000000000000100e+00 -4.069014309729406300e-01 2.319615721086100800e+00 3.299999999999999800e+00 -1.666155295956388300e-01 -2.497162196179187900e-01 3.500000000000000000e+00 0.000000000000000000e+00 -1.237130660986393100e+01 8 7.351364478015182100e-01 6.165217237728655200e-01 1 1 1 1 -1.770934559908718700e+00 -1.074925682941420000e+00 -1.482768170233858500e-01 -3.881557649503457600e-01 -2.004503493658201000e-01 -1.492100354067345500e-01 9.946230300080272100e-01 4.142241371345077300e-01 -7.012475119623896900e-02 2.377401824966400000e+00 8.793892953828742500e-01 -3.944355024164965900e-02 3.760180619924772900e+00 1.266888024536562100e+00 -1.581431192239436000e-02 5.142959414883146800e+00 1.629979548834614900e+00 2.611224310900800400e-02 6.525738209841518900e+00 1.977379549636293600e+00 -1.378738550324104500e-01 7.908517004799891800e+00 2.396177220616657200e+00 7.494253977092666400e-01 10 -3.618936018538757300e+00 0.000000000000000000e+00 1 0 1 0 1.500000000000000000e+00 1.250311510312851300e+00 2.790400588857243500e+01 1.722222222222222300e+00 8.682060369372680600e-01 -4.522554291731776900e+00 1.944444444444444400e+00 6.084604017544847900e-01 5.052931618779816800e+00 2.166666666666666500e+00 4.875624808097850400e-01 1.180825096539679600e+00 2.388888888888888800e+00 4.416345603457190700e-01 -6.673769465415171400e-01 2.611111111111111200e+00 3.760976313325982700e-01 -8.938118490837722000e-01 2.833333333333333000e+00 2.714524157414608400e-01 -5.090324763524399800e-01 3.055555555555555400e+00 1.481440300150710900e-01 6.623665830603995300e-01 3.277777777777777700e+00 4.854596610856590900e-02 7.403702452268122700e-01 3.500000000000000000e+00 0.000000000000000000e+00 2.578982318481970500e+00 8 -1.395041572145673000e+01 1.134616739799360700e+00 1 1 1 1 -1.000000000000000900e+00 5.254163992149617700e+00 1.582685381253900500e+01 -7.428367052748285900e-01 2.359149452448745100e+00 3.117611233789983400e+01 -4.856734105496561800e-01 1.195946960915646100e+00 1.658962813584905800e+01 -2.285101158244838800e-01 1.229952028074150000e+00 1.108360928564026400e+01 2.865317890068852500e-02 2.035650777568434500e+00 9.088861456447702400e+00 2.858164736258610400e-01 3.424741418405580000e+00 5.489943377538379500e+00 5.429797683510331200e-01 4.948585892304984100e+00 -1.882291580187675700e+01 8.001430630762056400e-01 5.617988713941801200e+00 -7.718625571850646200e+00 ``` ## MEAM/SW/SPLINE style The `meam/sw/spline` style supported by the driver is similar to the `meam/spline` style except for an additional Stillinger-Weber (SW) term that's added onto the energy. For this MEAM style, only a single species is supported. The total energy Ei of an atom I is given by, ```tex E_i = U_\alpha (\Bar{\rho}_i) + \frac{1}{2}\sum\limits_{j \ne i} \phi_{\alpha \beta}(r_{ij}) + {E_{SW}}_i, ``` where, ```tex {E_{SW}}_i = \sum\limits_{\substack{j < k, \\ j \ne i}} F_j(r_{ij}) F_k(r_{ik}) G_{jk}{\left(\cos(\theta_{jik})\right)}. ``` The atomic electron density is, ```tex \Bar{\rho}_i=\sum\limits_{j \ne i}\rho_j(r_{ij}) + \sum\limits_{\substack{j < k, \\ j \ne i}} f_j(r_{ij}) f_k(r_{ik}) g_{jk}{\left(\cos(\theta_{jik})\right)}, ``` where `rho` is the density, and `theta` is the angle between atoms. The seven functions `phi`, `U`, `F`, `G`, `rho`, `f`, and `g`, are represented by cubic splines. While the species name is in the element file, the potential file indicates the cutoffs and the coefficients for these spline functions. The MEAM potential file name usually contains the element's name and ends in the `.meam.sw.spline` extension. For example, for an Ti system, the `Ti.meam.sw.spline` file contains the specific parameter settings. ### MEAM/SW/SPLINE style example As an example, a KIM Portable Model (PM) for pure `Ti` system that uses this model driver with the `meam/sw/spline` style might contain the following two input files: ```bash elems.meam Ti.meam.sw.spline ``` where `elems.meam` element file would contain ```bash # list of elements # Elem1, Elem2 Ti ``` and the `Ti.meam.sw.spline` potential file might contain ```bash # DATE: 2012-02-01 UNITS: metal CONTRIBUTOR: Robert Rudd, robert.rudd@llnl.gov CITATION: Hennig, Lenosky, Trinkle, Rudin, and Wilkins, Phys Rev B, 78, 054121 (2008) COMMENT: Spline-based MEAM+SW potential for Ti (R.G. Hennig et al., Phys. Rev. B 78, 054121 (2008)). 13 -20.0 0.0 1 0 1 0 1.742692837163632546e+00 3.744277175966389349e+00 0.0e+00 2.055801767399996649e+00 9.108397309055012991e-01 1.087025233010940539e+01 2.368910697636360752e+00 3.880458966341450711e-01 -1.553224188359566327e+00 2.682019627872724410e+00 -1.884090653346989427e-02 2.436300413714785229e+00 2.995128558109088512e+00 -2.480989296390785637e-01 2.679127139950259640e+00 3.308237488345452615e+00 -2.644895502965277645e-01 -1.250563846088559861e-01 3.621346418581816273e+00 -2.271961892825972718e-01 1.106625553693794339e+00 3.934455348818180376e+00 -1.292930901760148965e-01 -5.920536767960294933e-01 4.247564279054544478e+00 -5.968536693320936753e-02 -4.701234146338039155e-01 4.560673209290908581e+00 -3.110002556084055444e-02 -3.807399733552661869e-02 4.873782139527271795e+00 -1.384736320244591042e-02 -7.115479604519592272e-02 5.186891069763635898e+00 -3.203412727856397215e-03 -8.176829245009833991e-02 5.500000000000000000e+00 0.000000000000000000e+00 -5.714229647754404118e-02 2 0.000000000000000000e+00 0.000000000000000000e+00 1 0 0 0 2.055801767399996649e+00 0.000000000000000000e+00 0.000000000000000000e+00 4.410000000000000142e+00 0.000000000000000000e+00 0.000000000000000000e+00 2 0.000000000000000000e+00 0.000000000000000000e+00 1 0 0 0 -1.000000000000000000e+00 0.000000000000000000e+00 0.000000000000000000e+00 9.284366193603559303e-01 0.000000000000000000e+00 0.000000000000000000e+00 11 -1.000000000000000000e+00 0.000000000000000000e+00 1 0 0 0 2.055801767399996649e+00 1.747527966078008976e+00 -5.258697870855910423e+02 2.291221590659997087e+00 -5.867796394513962177e+00 2.527963170143783884e+02 2.526641413919997525e+00 -8.337628873718182732e+00 7.173183889436359095e+01 2.762061237179997519e+00 -5.839871284245343297e+00 -1.935877422943027337e+00 2.997481060439997957e+00 -3.114064823053663389e+00 -3.929991928613325314e+01 3.232900883699998396e+00 -1.725724506500649014e+00 1.434241360892369954e+01 3.468320706959998834e+00 -4.428977016930342181e-01 -2.949255346943084177e+01 3.703740530219999272e+00 -1.466643003340316054e-01 -3.180105342079309949e+00 3.939160353479999266e+00 -2.095507944774975262e-01 3.334908384292152750e+00 4.174580176740000148e+00 -1.442384563223014227e-01 3.719186918672943154e+00 4.410000000000000142e+00 0.000000000000000000e+00 -9.667170204974903314e+00 4 7.769349460453946719e-03 1.051977061603435737e-01 1 1 1 1 -5.514233164927543385e+01 -2.974556800785587707e-01 1.528706039584923782e-03 -4.474098990370920603e+01 -1.544945872174040002e-01 3.893372250824005966e-04 -3.433964815814297822e+01 5.098657168053199323e-02 3.812492703804592413e-04 -2.393830641257674685e+01 5.734269470406565539e-01 1.566392648865140222e-02 10 2.773275116566607856e+00 0.000000000000000000e+00 1 0 1 0 2.055801767399996649e+00 -1.485215264177146000e-01 7.220108674930609993e+01 2.317379348799997185e+00 1.684530491819494546e+00 -4.727446892749223650e+01 2.578956930199997277e+00 2.011336597660079661e+00 -1.518595783989647252e+01 2.840534511599997813e+00 1.144409274729116577e+00 3.339782043718398263e+00 3.102112092999998350e+00 2.861606802608402389e-01 2.587867610190767831e+00 3.363689674399998442e+00 -3.459281125712435068e-01 6.140706938696685491e+00 3.625267255799998978e+00 -6.257480601030769307e-01 3.739769675678216831e+00 3.886844837199999514e+00 -6.119510825772711549e-01 4.647490848815326814e+00 4.148422418600000050e+00 -3.112059650865105498e-01 2.832757465268814556e+00 4.410000000000000142e+00 0.000000000000000000e+00 -1.506120868737344587e+01 8 8.336422748105723812e+00 -6.040245747365641193e+01 1 1 1 1 -1.000000000000001998e+00 7.651409192994791664e-02 -1.106523212957412881e+02 -7.245090543770936753e-01 1.415582454149486025e-01 4.488534055085228403e+01 -4.490181087541854632e-01 7.578869734074348274e-01 -2.530651153464005532e+01 -1.735271631312771679e-01 6.301157037831857100e-01 -2.485101449562865383e+00 1.019637824916310997e-01 9.049597305054708773e-02 2.687693869168511718e+00 3.774547281145393951e-01 -3.574158665670761348e-01 -1.015585700534352709e+00 6.529456737374476072e-01 -6.529321764728414079e-01 1.342247859683878808e+01 9.284366193603559303e-01 -6.009121906529053980e+00 -4.527525426982541035e+02 ``` ## References [1] M.I., Baskes, J.S., Nelson, and A.F., Wright, "Semiempirical modified embedded atom potentials for silicon and germanium," Phys. Rev.B, 40:6085--6100, Sep 1989. [2] M.I., Baskes, "Modified embedded atom potentials for cubic materials and impurities," Phys. Rev.B, 46:2727--2742, Aug 1992. [3] M.I., Baskes, "Determination of modified embedded atom method parameters for nickel," Materials Chemistry and Physics, 50(2):152--158, 1997. [4] B.J., Lee, and M.I., Baskes, "Second nearest-neighbor modified embedded atom method potential," Phys. Rev.B, 62:8564, Oct 2000. [5] B.J., Lee, M.I., Baskes, H., Kim, and Y.K., Cho, "Second nearest-neighbor modified embedded atom method potentials for bcc transition metals," Phys. Rev.B, 64:184102, Oct 2001. [6] S.M., Valone, M.I., Baskes, and R.L., Martin, "Atomistic model of helium bubbles in gallium-stabilized plutonium alloys," Phys. Rev.B 73:214209 June 2006. [7] H., Huang, N.M., Ghoniem, J.K., Wong, and M., Baskes, "Molecular dynamics determination of defect energetics in beta-SiC using three representative empirical potentials," Modelling and Simulation in Materials Science and Engineering, 3(5):615--627, Sep 1995. [8] T.J., Lenosky, B., Sadigh, E., Alonso, V.V., Bulatov, T.D., Rubia, J., Kim, A.F., Voter, and J.D., Kress, "Highly optimized empirical potential model of silicon," Modelling and Simulation in Materials Science and Engineering, 8(6):825--841, Oct 2000. [9] H., Fang, P.M., Gullett, A., Slepoy, M.F., Horstemeyer, M., Baskes, G.J., Wagner, and M., Li, "Numerical tools for atomistic simulations," Report 918395, Sandia National Laboratories, Jan 2004. [10] [https://lammps.org](https://lammps.org) [11] [https://docs.lammps.org/pair_meam.html](https://docs.lammps.org/pair_meam.html) [12] [https://docs.lammps.org/pair_meam_spline.html](https://docs.lammps.org/pair_meam_spline.html) [13] [https://docs.lammps.org/pair_meam_sw_spline.html](https://docs.lammps.org/pair_meam_sw_spline.html) [14] B.J., Thijsse, "Relationship between the modified embedded atom method and stillinger-weber potentials in calculating the structure of silicon," Phys. Rev. B, 65:195207, May 2002. [15] B., Jelinek, S., Groh, M.F., Horstemeyer, J., Houze, S.G., Kim, G.J., Wagner, A., Moitra, and M.I., Baskes, "Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys," Phys. Rev. B, 85:245102, Jun 2012. [16] M.R., Fellinger, "First principles-based interatomic potentials for modeling the body-bentered cubic metals V, Nb, Ta, Mo, and W," Ph.D. thesis, The Ohio State University, Jan 2013. [17] P., Zhang and D.R., Trinkle, "A modified embedded atom method potential for interstitial oxygen in titanium," Computational Materials Science, 124:204--210, Nov 2016. [18] A.P. Moore and B. Beeler and C. Deo and M.I. Baskes and M.A. Okuniewski, "Atomistic modeling of high temperature uranium–zirconium alloy structure and thermodynamics," Journal of Nuclear Materials, 467:802--819, 2015. ## License [LGPLv2.1](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html) ## Copyright ```txt LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator https://lammps.org, Sandia National Laboratories Steve Plimpton, sjplimp@sandia.gov Copyright (2003) Sandia Corporation. Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains certain rights in this software. This software is distributed under the GNU General Public License. ``` ```txt Copyright (2011) Lawrence Livermore National Security, LLC. Produced at the Lawrence Livermore National Laboratory. Written by Alexander Stukowski (). LLNL-CODE-525797 All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (as published by the Free Software Foundation) version 2, dated June 1991. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and conditions of the GNU General Public License for more details. Our Preamble Notice A. This notice is required to be provided under our contract with the U.S. Department of Energy (DOE). This work was produced at the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with the DOE. B. Neither the United States Government nor Lawrence Livermore National Security, LLC nor any of their employees, makes any warranty, express or implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately-owned rights. C. Also, reference herein to any specific commercial products, process, or services by trade name, trademark, manufacturer or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes. ``` ```txt Copyright (2012) Lawrence Livermore National Security, LLC. Produced at the Lawrence Livermore National Laboratory. Written by Robert E. Rudd (). Based on the spline MEAM routine written by Alexander Stukowski (). LLNL-CODE-588032 All rights reserved. The spline-based MEAM+SW format was first devised and used to develop potentials for bcc transition metals by Jeremy Nicklas, Michael Fellinger, and Hyoungki Park at The Ohio State University. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (as published by the Free Software Foundation) version 2, dated June 1991. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and conditions of the GNU General Public License for more details. Our Preamble Notice A. This notice is required to be provided under our contract with the U.S. Department of Energy (DOE). This work was produced at the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with the DOE. B. Neither the United States Government nor Lawrence Livermore National Security, LLC nor any of their employees, makes any warranty, express or implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately-owned rights. C. Also, reference herein to any specific commercial products, process, or services by trade name, trademark, manufacturer or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes. ``` ```txt Copyright (c) 2021, Regents of the University of Minnesota. All rights reserved. ``` ## Contributing Contributors:\       Yaser Afshar (UMN),\       Daniel S. Karls (UMN) Contributing authors, original code in the LAMMPS USER-MEAM package (MEAM):\       Greg Wagner (SNL),\       Sebastian Hütter (OvGU) Contributing authors, original code in the LAMMPS MANYBODY package (MEAM/SPLINE):\       Alexander Stukowski (LLNL),\       Will Tipton (Cornell),\       Dallas R. Trinkle (UIUC),\       Pinchao Zhang (UIUC),\       Robert Rudd (LLNL) Contributing authors, original code in the LAMMPS MANYBODY package (MEAM/SW/SPLINE):\       Robert Rudd (LLNL)