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Citation: X.W. Zhou, D.K. Ward, and M.E. Foster (2015), "An analytical bond-order potential for carbon", Journal of Computational Chemistry, 36(23), 1719-1735. DOI: 10.1002/jcc.23949.
Abstract: Carbon is the most widely studied material today because it exhibits special properties not seen in any other materials when in nano dimensions such as nanotube and graphene. Reduction of material defects created during synthesis has become critical to realize the full potential of carbon structures. Molecular dynamics (MD) simulations, in principle, allow defect formation mechanisms to be studied with high fidelity, and can, therefore, help guide experiments for defect reduction. Such MD simulations must satisfy a set of stringent requirements. First, they must employ an interatomic potential formalism that is transferable to a variety of carbon structures. Second, the potential needs to be appropriately parameterized to capture the property trends of important carbon structures, in particular, diamond, graphite, graphene, and nanotubes. Most importantly, the potential must predict the crystalline growth of the correct phases during direct MD simulations of synthesis to achieve a predictive simulation of defect formation. Because an unlimited number of structures not included in the potential parameterization are encountered, the literature carbon potentials are often not sufficient for growth simulations. We have developed an analytical bond order potential for carbon, and have made it available through the public MD simulation package LAMMPS. We demonstrate that our potential reasonably captures the property trends of important carbon phases. Stringent MD simulations convincingly show that our potential accounts not only for the crystalline growth of graphene, graphite, and carbon nanotubes but also for the transformation of graphite to diamond at high pressure.

LAMMPS pair_style bop (2015--Zhou-X-W--C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by X.W. Zhou (Sandia)
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Citation: J.H. Los, and A. Fasolino (2003), "Intrinsic long-range bond-order potential for carbon: Performance in Monte Carlo simulations of graphitization", Physical Review B, 68(2), . DOI: 10.1103/physrevb.68.024107.
Abstract: We propose a bond order potential for carbon with built-in long-range interactions. The potential is defined as the sum of an angular and coordination dependent short-range part accounting for the strong covalent interactions and a radial long-range part describing the weak interactions responsible, e.g., for the interplanar binding in graphite. The short-range part is a Brenner type of potential, with several modifications introduced to get an improved description of elastic properties and conjugation. Contrary to previous long-range extensions of existing bond order potentials, we prevent the loss of accuracy by compensating for the additional long-range interactions by an appropriate parametrization of the short-range part. We also provide a short-range bond order potential. In Monte Carlo simulations our potential gives a good description of the diamond to graphite transformation. For thin (111) slabs graphitization proceeds perpendicular to the surface as found in ab initio simulations, whereas for thick layers we find that graphitization occurs layer by layer.

LAMMPS pair_style lcbop (2003--Los-J-H--C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution. The LAMMPS documentation for pair_style lcbop notes "The parameters/coefficients for the LCBOP potential as applied to C are listed in the C.lcbop file to agree with the original (Los and Fasolino) paper. Thus the parameters are specific to this potential and the way it was fit, so modifying the file should be done carefully."
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Citation: A. Kınacı, J.B. Haskins, C. Sevik, and T. Çağın (2012), "Thermal conductivity of BN-C nanostructures", Physical Review B, 86(11), . DOI: 10.1103/physrevb.86.115410.
Abstract: Chemical and structural diversity present in hexagonal boron nitride (h-BN) and graphene hybrid nanostructures provide avenues for tuning various properties for their technological applications. In this paper we investigate the variation of thermal conductivity (κ) of hybrid graphene/h-BN nanostructures: stripe superlattices and BN (graphene) dots embedded in graphene (BN) are investigated using equilibrium molecular dynamics. To simulate these systems, we have parametrized a Tersoff type interaction potential to reproduce the ab initio energetics of the B-C and N-C bonds for studying the various interfaces that emerge in these hybrid nanostructures. We demonstrate that both the details of the interface, including energetic stability and shape, as well as the spacing of the interfaces in the material, exert strong control on the thermal conductivity of these systems. For stripe superlattices, we find that zigzag configured interfaces produce a higher κ in the direction parallel to the interface than the armchair configuration, while the perpendicular conductivity is less prone to the details of the interface and is limited by the κ of h-BN. Additionally, the embedded dot structures, having mixed zigzag and armchair interfaces, affect the thermal transport properties more strongly than superlattices. The largest reduction in thermal conductivity is observed at 50% dot concentration, but the dot radius appears to have little effect on the magnitude of reduction around this concentration.

LAMMPS pair_style tersoff (2012--Kinaci-A--B-N-C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
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Citation: X.W. Zhou, D.K. Ward, and M.E. Foster (2015), "An analytical bond-order potential for carbon", Journal of Computational Chemistry, 36(23), 1719-1735. DOI: 10.1002/jcc.23949.
Abstract: Carbon is the most widely studied material today because it exhibits special properties not seen in any other materials when in nano dimensions such as nanotube and graphene. Reduction of material defects created during synthesis has become critical to realize the full potential of carbon structures. Molecular dynamics (MD) simulations, in principle, allow defect formation mechanisms to be studied with high fidelity, and can, therefore, help guide experiments for defect reduction. Such MD simulations must satisfy a set of stringent requirements. First, they must employ an interatomic potential formalism that is transferable to a variety of carbon structures. Second, the potential needs to be appropriately parameterized to capture the property trends of important carbon structures, in particular, diamond, graphite, graphene, and nanotubes. Most importantly, the potential must predict the crystalline growth of the correct phases during direct MD simulations of synthesis to achieve a predictive simulation of defect formation. Because an unlimited number of structures not included in the potential parameterization are encountered, the literature carbon potentials are often not sufficient for growth simulations. We have developed an analytical bond order potential for carbon, and have made it available through the public MD simulation package LAMMPS. We demonstrate that our potential reasonably captures the property trends of important carbon phases. Stringent MD simulations convincingly show that our potential accounts not only for the crystalline growth of graphene, graphite, and carbon nanotubes but also for the transformation of graphite to diamond at high pressure.

Notes: Notes from Dr. Zhou about the C-Cu interactions: "The C-Cu potential was constructed from the carbon potential (2015--Zhou-X-W-Ward-D-K-Foster-M-E--C) and Cu of the Al-Cu and Cu-H potentials (2016--Zhou-X-W-Ward-D-K-Foster-M-E--Al-Cu, 2015--Zhou-X-W-Ward-D-K-Foster-M-Zimmerman-J-A--Cu-H), except that a Morse potential is added to the Cu so that the cohesive energy of Cu is deliberately significantly increased but the lattice constant of Cu is unchanged. This allows simulations of growth of C on Cu to be performed at temperatures higher than the Cu melting temperature (to accelerate the simulations) without other negative consequencies."

LAMMPS pair_style bop (2015--Zhou-X-W--C-Cu--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution and listed as having been created by X.W. Zhou (Sandia)
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Citation: L.S.I. Liyanage, S.-G. Kim, J. Houze, S. Kim, M.A. Tschopp, M.I. Baskes, and M.F. Horstemeyer (2014), "Structural, elastic, and thermal properties of cementite (Fe3C) calculated using a modified embedded atom method", Physical Review B, 89(9), 94102. DOI: 10.1103/physrevb.89.094102.
Abstract: Structural, elastic, and thermal properties of cementite (Fe3C) were studied using a modified embedded atom method (MEAM) potential for iron-carbon (Fe-C) alloys. Previously developed Fe and C single-element potentials were used to develop a Fe-C alloy MEAM potential, using a statistics-based optimization scheme to reproduce structural and elastic properties of cementite, the interstitial energies of C in bcc Fe, and heat of formation of Fe-C alloys in L12 and B1 structures. The stability of cementite was investigated by molecular dynamics simulations at high temperatures. The nine single-crystal elastic constants for cementite were obtained by computing total energies for strained cells. Polycrystalline elastic moduli for cementite were calculated from the single-crystal elastic constants of cementite. The formation energies of (001), (010), and (100) surfaces of cementite were also calculated. The melting temperature and the variation of specific heat and volume with respect to temperature were investigated by performing a two-phase (solid/liquid) molecular dynamics simulation of cementite. The predictions of the potential are in good agreement with first-principles calculations and experiments.

LAMMPS pair_style meam (2014--Liyanage-L-S-I--Fe-C--LAMMPS--ipr2)
Notes: These files were contributed by Laalitha Liyanage (Central Michigan Univ., Univ. of North Texas) on 14 Apr. 2014.
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Citation: K.O.E. Henriksson, C. Björkas, and K. Nordlund (2013), "Atomistic simulations of stainless steels: a many-body potential for the Fe-Cr-C system", Journal of Physics: Condensed Matter, 25(44), 445401. DOI: 10.1088/0953-8984/25/44/445401.
Abstract: Stainless steels found in real-world applications usually have some C content in the base Fe–Cr alloy, resulting in hard and dislocation-pinning carbides—Fe3C (cementite) and Cr23C6—being present in the finished steel product. The higher complexity of the steel microstructure has implications, for example, for the elastic properties and the evolution of defects such as Frenkel pairs and dislocations. This makes it necessary to re-evaluate the effects of basic radiation phenomena and not simply to rely on results obtained from purely metallic Fe–Cr alloys. In this report, an analytical interatomic potential parameterization in the Abell–Brenner–Tersoff form for the entire Fe–Cr–C system is presented to enable such calculations. The potential reproduces, for example, the lattice parameter(s), formation energies and elastic properties of the principal Fe and Cr carbides (Fe3C, Fe5C2, Fe7C3, Cr3C2, Cr7C3, Cr23C6), the Fe–Cr mixing energy curve, formation energies of simple C point defects in Fe and Cr, and the martensite lattice anisotropy, with fair to excellent agreement with empirical results. Tests of the predictive power of the potential show, for example, that Fe–Cr nanowires and bulk samples become elastically stiffer with increasing Cr and C concentrations. High-concentration nanowires also fracture at shorter relative elongations than wires made of pure Fe. Also, tests with Fe3C inclusions show that these act as obstacles for edge dislocations moving through otherwise pure Fe.

Notes: Note that this entry only represents the Fe-C subset of interatomic potentials developed and used in this reference.

LAMMPS pair_style tersoff/zbl (2013--Henriksson-K-O-E--Fe-C--LAMMPS--ipr1)
Notes: The Tersoff/ZBL file was contributed by Astrid Gubbels-Elzas and Peter Klaver (Delft University of Technology, Netherlands) and posted with their approval and that of Krister Henriksson (Univ. of Helsinki, Finland) on 9 Jul. 2014. Note that this file only represents the Fe-C subset of interatomic potentials developed and used in this reference.
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EAM tabulated functions
Notes: The following files were contributed by Dr. Henriksson and modified by C. Becker to include the reference and format in the header information. They represent the potential in Equation 7 of the reference, and the columns are r, VZBL, and d/dr (VZBL). They were approved by Dr. Henriksson for posting on 25 Jul. 2014.
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Citation: D.J. Hepburn, and G.J. Ackland (2008), "Metallic-covalent interatomic potential for carbon in iron", Physical Review B, 78(16), 165115. DOI: 10.1103/physrevb.78.165115.
Abstract: Existing interatomic potentials for the iron-carbon system suffer from qualitative flaws in describing even the simplest of defects. In contrast to more accurate first-principles calculations, all previous potentials show strong bonding of carbon to overcoordinated defects (e.g., self-interstitials, dislocation cores) and a failure to accurately reproduce the energetics of carbon-vacancy complexes. Thus any results from their application in molecular dynamics to more complex environments are unreliable. The problem arises from a fundamental error in potential design—the failure to describe short-ranged covalent bonding of the carbon p electrons. We describe a resolution to the problem and present an empirical potential based on insights from density-functional theory, showing covalent-type bonding for carbon. The potential correctly describes the interaction of carbon and iron across a wide range of defect environments. It has the embedded atom method form and hence appropriate for billion atom molecular-dynamics simulations.

LAMMPS pair_style eam/fs (2008--Hepburn-D-J--Fe-C--LAMMPS--ipr1)
Notes: This file was implemented in the LAMMPS-compatible EAM/FS format by Sebastien Garruchet and posted with the permission of G.J. Ackland on 13 May 2009.
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Citation: H.-K. Kim, W.-S. Jung, and B.-J. Lee (2009), "Modified embedded-atom method interatomic potentials for the Fe-Ti-C and Fe-Ti-N ternary systems", Acta Materialia, 57(11), 3140-3147. DOI: 10.1016/j.actamat.2009.03.019.
Abstract: Modified embedded-atom method (MEAM) interatomic potentials for the Fe–Ti–C and Fe–Ti–N ternary systems have been developed based on the previously developed MEAM potentials for sub-unary and binary systems. An attempt was made to find a way to determine ternary potential parameters using the corresponding binary parameters. The calculated coherent interface properties, interfacial energy, work of separation and misfit strain energy between body-centered cubic Fe and NaCl-type TiC or TiN were reasonable when compared with relevant first-principles calculations under the same condition. The applicability of the present potentials for atomistic simulations to investigate nucleation kinetics of TiC or TiN precipitates and their effects on mechanical properties in steels is also demonstrated.

LAMMPS pair_style meam (2009--Kim-H-K--Fe-Ti-C--LAMMPS--ipr2)
Notes: This file was submitted by Sebastián ECHEVERRI RESTREPO (SKF Engineering & Research Centre) on 31 August 2015 and approved for distribution by Byeong-Joo Lee (POSTECH). This version is compatible with LAMMPS. Implementation information can be found in FeTiC_Implementation.pdf.
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Citation: K. Chenoweth, A.C.T. van Duin, and W.A. Goddard (2008), "ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation", The Journal of Physical Chemistry A, 112(5), 1040-1053. DOI: 10.1021/jp709896w.
Abstract: To investigate the initial chemical events associated with high-temperature gas-phase oxidation of hydrocarbons, we have expanded the ReaxFF reactive force field training set to include additional transition states and chemical reactivity of systems relevant to these reactions and optimized the force field parameters against a quantum mechanics (QM)-based training set. To validate the ReaxFF potential obtained after parameter optimization, we performed a range of NVT−MD simulations on various hydrocarbon/O2 systems. From simulations on methane/O2, o-xylene/O2, propene/O2, and benzene/O2 mixtures, we found that ReaxFF obtains the correct reactivity trend (propene > o-xylene > methane > benzene), following the trend in the C−H bond strength in these hydrocarbons. We also tracked in detail the reactions during a complete oxidation of isolated methane, propene, and o-xylene to a CO/CO2/H2O mixture and found that the pathways predicted by ReaxFF are in agreement with chemical intuition and our QM results. We observed that the predominant initiation reaction for oxidation of methane, propene, and o-xylene under fuel lean conditions involved hydrogen abstraction of the methyl hydrogen by molecular oxygen forming hydroperoxyl and hydrocarbon radical species. While under fuel rich conditions with a mixture of these hydrocarbons, we observed different chemistry compared with the oxidation of isolated hydrocarbons including a change in the type of initiation reactions, which involved both decomposition of the hydrocarbon or attack by other radicals in the system. Since ReaxFF is capable of simulating complicated reaction pathways without any preconditioning, we believe that atomistic modeling with ReaxFF provides a useful method for determining the initial events of oxidation of hydrocarbons under extreme conditions and can enhance existing combustion models.

ReaxFF (2008--Chenoweth-K--C-H-O--LAMMPS--ipr1)
Notes: The file "ffield.reax.CHO_2008" was provided by Adri van Duin. From Prof. van Duin: "The ffield-file contains the force field parameters; this file is readable by LAMMPS." The ReaxFF manual (including file formatting information) was obtained from http://www.wag.caltech.edu/home/duin/manual.html. All files were posted with Prof. van Duin's approval. The standalone ReaxFF program is available without charge for academic users by emailing him.
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Citation: C. Jiang, D. Morgan, and I. Szlufarska (2012), "Carbon tri-interstitial defect: A model for the DII center", Physical Review B, 86(14), . DOI: 10.1103/physrevb.86.144118.
Abstract: Using a combination of random configuration sampling, molecular dynamics simulated annealing with empirical potential, and ensuing structural refinement by first-principles density functional calculations, we perform an extensive ground-state search for the most stable configurations of small carbon interstitial clusters in SiC. Our search reveals a "magic" cluster number of three atoms, where the formation energy per interstitial shows a distinct minimum. A carbon tri-interstitial cluster with trigonal C3v symmetry is discovered, in which all carbon atoms are fourfold coordinated. In addition to its special thermodynamic stability, its localized vibrational modes are also in a very good agreement with the experimental photoluminescence spectra of the DII center in both 3C- and 4H-SiC. The DII center is one of the most persistent defects in SiC, and we propose that the discovered carbon tri-interstitial is responsible for this center.

LAMMPS pair_style edip/multi (2012--Jiang-C--Si-C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution. It is listed as being contributed by Chao Jiang (University of Wisconsin)
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Citation: P. Vashishta, R.K. Kalia, A. Nakano, and J.P. Rino (2007), "Interaction potential for silicon carbide: A molecular dynamics study of elastic constants and vibrational density of states for crystalline and amorphous silicon carbide", Journal of Applied Physics, 101(10), 103515. DOI: 10.1063/1.2724570.
Abstract: An effective interatomic interaction potential for SiC is proposed. The potential consists of two-body and three-body covalent interactions. The two-body potential includes steric repulsions due to atomic sizes, Coulomb interactions resulting from charge transfer between atoms, charge-induced dipole-interactions due to the electronic polarizability of ions, and induced dipole-dipole (van der Waals) interactions. The covalent characters of the Si–C–Si and C–Si–C bonds are described by the three-body potential. The proposed three-body interaction potential is a modification of the Stillinger-Weber form proposed to describe Si. Using the molecular dynamics method, the interaction potential is used to study structural, elastic, and dynamical properties of crystalline (3C), amorphous, and liquid states of SiC for several densities and temperatures. The structural energy for cubic (3C) structure has the lowest energy, followed by the wurtzite (2H) and rock-salt (RS) structures. The pressure for the structural transformation from 3C-to-RS from the common tangent is found to be 90 GPa. For 3C-SiC, our computed elastic constants (C11, C12, and C44), melting temperature, vibrational density-of-states, and specific heat agree well with the experiments. Predictions are made for the elastic constant as a function of density for the crystalline and amorphous phase. Structural correlations, such as pair distribution function and neutron and x-ray static structure factors are calculated for the amorphous and liquid state.

LAMMPS pair_style vashishta (2007--Vashishta-P--Si-C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
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Citation: P. Erhart, and K. Albe (2005), "Analytical potential for atomistic simulations of silicon, carbon, and silicon carbide", Physical Review B, 71(3), . DOI: 10.1103/physrevb.71.035211.
Abstract: We present an analytical bond-order potential for silicon, carbon, and silicon carbide that has been optimized by a systematic fitting scheme. The functional form is adopted from a preceding work [Phys. Rev. B 65, 195124 (2002)] and is built on three independently fitted potentials for Si-Si, C-C, and Si-C interaction. For elemental silicon and carbon, the potential perfectly reproduces elastic properties and agrees very well with first-principles results for high-pressure phases. The formation enthalpies of point defects are reasonably reproduced. In the case of silicon stuctural features of the melt agree nicely with data taken from literature. For silicon carbide the dimer as well as the solid phases B1, B2, and B3 were considered. Again, elastic properties are very well reproduced including internal relaxations under shear. Comparison with first-principles data on point defect formation enthalpies shows fair agreement. The successful validation of the potentials for configurations ranging from the molecular to the bulk regime indicates the transferability of the potential model and makes it a good choice for atomistic simulations that sample a large configuration space.

Notes: This entry uses the paper's Si-I interaction, which was recommended for SiC simulations.

LAMMPS pair_style tersoff (2005--Erhart-P--Si-C-I--LAMMPS--ipr1)
Notes: This file was created and verified by Lucas Hale. The parameter values are comparable to those in the SiC_Erhart-Albe.tersoff file in the August 22, 2018 LAMMPS distribution with this file using higher precision for the derived parameters.
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Citation: P. Erhart, and K. Albe (2005), "Analytical potential for atomistic simulations of silicon, carbon, and silicon carbide", Physical Review B, 71(3), . DOI: 10.1103/physrevb.71.035211.
Abstract: We present an analytical bond-order potential for silicon, carbon, and silicon carbide that has been optimized by a systematic fitting scheme. The functional form is adopted from a preceding work [Phys. Rev. B 65, 195124 (2002)] and is built on three independently fitted potentials for Si-Si, C-C, and Si-C interaction. For elemental silicon and carbon, the potential perfectly reproduces elastic properties and agrees very well with first-principles results for high-pressure phases. The formation enthalpies of point defects are reasonably reproduced. In the case of silicon stuctural features of the melt agree nicely with data taken from literature. For silicon carbide the dimer as well as the solid phases B1, B2, and B3 were considered. Again, elastic properties are very well reproduced including internal relaxations under shear. Comparison with first-principles data on point defect formation enthalpies shows fair agreement. The successful validation of the potentials for configurations ranging from the molecular to the bulk regime indicates the transferability of the potential model and makes it a good choice for atomistic simulations that sample a large configuration space.

Notes: This entry uses the paper's Si-II interaction, which gives better elastic and thermal properties for elemental silicon.

LAMMPS pair_style tersoff (2005--Erhart-P--Si-C-II--LAMMPS--ipr1)
Notes: This file was created and verified by Lucas Hale. The parameter values are identical to the ones in the parameter file used by openKIM model MO_408791041969_001.
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Citation: R. Devanathan, T. Diaz de la Rubia, and W.J. Weber (1998), "Displacement threshold energies in β-SiC", Journal of Nuclear Materials, 253(1-3), 47-52. DOI: 10.1016/s0022-3115(97)00304-8.
Abstract: We have calculated the displacement threshold energies (Ed) for C and Si primary knock-on atoms (PKA) in β-SiC using molecular dynamic simulations. The interactions between atoms were modeled using a modified form of the Tersoff potential in combination with a realistic repulsive potential obtained from density-functional theory calculations. The simulation cell was cubic, contained 8000 atoms and had periodic boundaries. The temperature of the simulation was about 150 K. Our results indicate strong anisotropy in the Ed values for both Si and C PKA. The displacement threshold for Si varies from about 36 eV along [001] to 113 eV along [111], while Ed for C varies from 28 eV along [111] to 71 eV along [111]. These results are in good agreement with experimental observations.

LAMMPS pair_style tersoff/zbl (1998--Devanathan-R--Si-C--LAMMPS--ipr1)
Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
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Citation: J. Tersoff (1994), "Chemical order in amorphous silicon carbide", Physical Review B, 49(23), 16349-16352. DOI: 10.1103/physrevb.49.16349.
Abstract: While ordering in alloy crystals is well understood, short-range ordering in amorphous alloys remains controversial. Here, by studying computer-generated models of amorphous SiC, we show that there are two principal factors controlling the degree of chemical order in amorphous covalent alloys. One, the chemical preference for mixed bonds, is much the same in crystalline and amorphous materials. However, the other factor, the atomic size difference, is far less effective at driving ordering in amorphous material than in the crystal. As a result, the amorphous phase may show either strong ordering (as in GaAs), or weaker ordering (as in SiC), depending upon the relative importance of these two factors.

Notes: This parameterization uses the interactions of 1990--Tersoff-J--Si-C and the cutoff of 1989--Tersoff-J--Si-C, with a slight correction for heat of mixing.

LAMMPS pair_style tersoff (1994--Tersoff-J--Si-C--LAMMPS--ipr1)
Notes: This file was created and verified by Lucas Hale. The parameter values are comparable to the SiC_1994.tersoff file in the August 22, 2018 LAMMPS distribution, with this file having higher numerical precision for the derived mixing parameters.
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Citation: J. Tersoff (1990), "Carbon defects and defect reactions in silicon", Physical Review Letters, 64(15), 1757-1760. DOI: 10.1103/physrevlett.64.1757.
Abstract: The energies of carbon defects in silicon are calculated, using an empirical classical potential, and used to infer defect properties and reactions. Substitutional carbon is found to react with silicon interstitials, with the carbon "kicked out" to form a (100) split interstitial. This interstitial can in turn bind to a second substitutional carbon, relieving stress, in three configurations with similar energies. The results here accord well with a variety of experimental data, including defect structures, activation energies for defect motion, and coupling to strain. A discrepancy with the accepted values for carbon solubility in silicon suggests a reinterpretation of the experimental data.

Notes: This parameterization focused on studying C interstitials in bulk Si. It has a sharp cutoff not suited for unconstrained simulations.

LAMMPS pair_style tersoff (1990--Tersoff-J--Si-C--LAMMPS--ipr1)
Notes: This file was created and verified by Lucas Hale. The parameter values are comparable to the SiC_1990.tersoff file in the August 22, 2018 LAMMPS distribution, with this file having higher numerical precision for the derived mixing parameters.
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Citation: J. Tersoff (1989), "Modeling solid-state chemistry: Interatomic potentials for multicomponent systems", Physical Review B, 39(8), 5566-5568. DOI: 10.1103/physrevb.39.5566.
Abstract: A general form is proposed for an empirical interatomic potential for multicomponent systems. This form interpolates between potentials for the respective elements to treat heteronuclear bonds. The approach is applied to C-Si and Si-Ge systems. In particular, the properties of SiC and its defects are well described.
Citation: J. Tersoff (1990), "Erratum: Modeling solid-state chemistry: Interatomic potentials for multicomponent systems", Physical Review B, 41(5), 3248-3248. DOI: 10.1103/physrevb.41.3248.2.

Notes: This is Tersoff's original multicomponent potential for Si-C interactions.

LAMMPS pair_style tersoff (1989--Tersoff-J--Si-C--LAMMPS--ipr1)
Notes: This file was created and verified by Lucas Hale. The parameter values are comparable to the Si(D)-C interactions in SiCGe.tersoff file in the August 22, 2018 LAMMPS distribution, with this file having higher numerical precision for the derived mixing parameters. The parameters are identical to those in the parameter file used by openKIM model MO_171585019474_001.
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Citation: S. Nouranian, M.A. Tschopp, S.R. Gwaltney, M.I. Baskes, and M.F. Horstemeyer (2014), "An interatomic potential for saturated hydrocarbons based on the modified embedded-atom method", Physical Chemistry Chemical Physics, 16(13), 6233-6249. DOI: 10.1039/c4cp00027g.
Abstract: In this work, we developed an interatomic potential for saturated hydrocarbons using the modified embedded-atom method (MEAM), a reactive semi-empirical many-body potential based on density functional theory and pair potentials. We parameterized the potential by fitting to a large experimental and first-principles (FP) database consisting of (1) bond distances, bond angles, and atomization energies at 0 K of a homologous series of alkanes and their select isomers from methane to n-octane, (2) the potential energy curves of H2, CH, and C2 diatomics, (3) the potential energy curves of hydrogen, methane, ethane, and propane dimers, i.e., (H2)2, (CH4)2, (C2H6)2, and (C3H8)2, respectively, and (4) pressure–volume–temperature (PVT) data of a dense high-pressure methane system with the density of 0.5534 g cc−1. We compared the atomization energies and geometries of a range of linear alkanes, cycloalkanes, and free radicals calculated from the MEAM potential to those calculated by other commonly used reactive potentials for hydrocarbons, i.e., second-generation reactive empirical bond order (REBO) and reactive force field (ReaxFF). MEAM reproduced the experimental and/or FP data with accuracy comparable to or better than REBO or ReaxFF. The experimental PVT data for a relatively large series of methane, ethane, propane, and butane systems with different densities were predicted reasonably well by the MEAM potential. Although the MEAM formalism has been applied to atomic systems with predominantly metallic bonding in the past, the current work demonstrates the promising extension of the MEAM potential to covalently bonded molecular systems, specifically saturated hydrocarbons and saturated hydrocarbon-based polymers. The MEAM potential has already been parameterized for a large number of metallic unary, binary, ternary, carbide, nitride, and hydride systems, and extending it to saturated hydrocarbons provides a reliable and transferable potential for atomistic/molecular studies of complex material phenomena involving hydrocarbon–metal or polymer–metal interfaces, polymer–metal nanocomposites, fracture and failure in hydrocarbon-based polymers, etc. The latter is especially true since MEAM is a reactive potential that allows for dynamic bond formation and bond breaking during simulation. Our results show that MEAM predicts the energetics of two major chemical reactions for saturated hydrocarbons, i.e., breaking a C–C and a C–H bond, reasonably well. However, the current parameterization does not accurately reproduce the energetics and structures of unsaturated hydrocarbons and, therefore, should not be applied to such systems.

Notes: Dr. Sasan Nouranian (Center for Advanced Vehicular Systems, Mississippi State Univ.) noted: "These MEAM parameters for elements C and H as well as the diatomic CH are appropriate for energy minimization and reactive molecular dynamics simulations of SATURATED hydrocarbons, where all carbon atoms have the sp3 hybridization (single C-C bonds). At the current state, MEAM cannot handle unsaturated compounds with great accuracy. Furthermore, these C and H parameters are not appropriate for diamond and graphite systems. For the first time, MEAM can be used to simulate hydrocarbons and hydrocarbon/metal systems, since it has a large parameter database for major metals in the periodic table of elements. Since MEAM is a reactive potential, it can also be used to simulate fracture and fatigue in hydrocarbon-based polymers, such as polyethylene and polypropylene and their composites with nanometals as well as polymer/metal interfaces."

LAMMPS pair_style meam (2014--Nouranian-S--CH--ipr1)
Notes: These files were contributed by Sasan Nouranian (Center for Advanced Vehicular Systems, Mississippi State Univ.) on 1 Jul. 2014. An example of energy minimization for an isobutane molecule using the MEAM potential in LAMMPS is also included (Isobutane.in and Isobutane.dat).
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Date Created: October 5, 2010 | Last updated: November 09, 2018