× Updated! Potentials that share interactions are now listed as related models.
 
Citation: L.C. Erhard, J. Rohrer, K. Albe, and V.L. Deringer (2022), "A machine-learned interatomic potential for silica and its relation to empirical models", npj Computational Materials, 8(1), 90. DOI: 10.1038/s41524-022-00768-w.
Abstract: Silica (SiO2) is an abundant material with a wide range of applications. Despite much progress, the atomistic modelling of the different forms of silica has remained a challenge. Here we show that by combining density-functional theory at the SCAN functional level with machine-learning-based interatomic potential fitting, a range of condensed phases of silica can be accurately described. We present a Gaussian approximation potential model that achieves high accuracy for the thermodynamic properties of the crystalline phases, and we compare its performance (and performance-cost trade-off) with that of multiple empirically fitted interatomic potentials for silica. We also include amorphous phases, assessing the ability of the potentials to describe structures of melt-quenched glassy silica, their energetic stability, and the high-pressure structural transition to a mainly sixfold-coordinated phase. We suggest that rather than standing on their own, machine-learned potentials for silica may be used in conjunction with suitable empirical models, each having a distinct role and complementing the other, by combining the advantages of the long simulation times afforded by empirical potentials and the near-quantum-mechanical accuracy of machine-learned potentials. This way, our work is expected to advance atomistic simulations of this key material and to benefit further computational studies in the field.

Notes: The potential was designed for crystalline, amorphous and liquid silica and shows also good behavior for certain high-pressure phases. It is not tested for silica surfaces and non stoichiometric phases (non SiO2).

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Notes: These files were provided by Linus Erhard on Nov 1, 2022, and are alternatively available at the links listed below. For running the potential the QUIP package within LAMMPS is necessary. The file pot.in gives an example of the LAMMPS inputs to use to run this potential. Alternatively, the potential can be used in a python-ase interface called quippy.
File(s): Link(s):
zenodo, includes training data https://doi.org/10.5281/zenodo.6353684

Citation: E. Lee, K.-R. Lee, M.I. Baskes, and B.-J. Lee (2016), "A modified embedded-atom method interatomic potential for ionic systems: 2NNMEAM+Qeq", Physical Review B, 93(14), 144110. DOI: 10.1103/physrevb.93.144110.
Abstract: An interatomic potential model that can simultaneously describe metallic, covalent, and ionic bonding is suggested by combining the second nearest-neighbor modified embedded-atom method (2NNMEAM) and the charge equilibration (Qeq) method, as a further improvement of a series of existing models. Paying special attention to the removal of known problems found in the original Qeq model, a mathematical form for the atomic energy is newly developed, and carefully selected computational techniques are adapted for energy minimization, summation of Coulomb interaction, and charge representation. The model is applied to the Ti-O and Si-O binary systems selected as representative oxide systems for a metallic element and a covalent element. The reliability of the present 2NNMEAM+Qeq potential is evaluated by calculating the fundamental physical properties of a wide range of titanium and silicon oxides and comparing them with experimental data, density functional theory calculations, and other calculations based on (semi-)empirical potential models.

hybrid/overlay coul/streitz meam (2016--Lee-E--Si-O--LAMMPS--ipr1)
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Notes: These files were obtained from http://cmse.postech.ac.kr/home_2nnmeam, accessed Nov 9, 2020.More information on using the 2NNMEAM-QEQ potentials can be found at https://cmse.postech.ac.kr/lammps/140341.
File(s):
Citation: S. Munetoh, T. Motooka, K. Moriguchi, and A. Shintani (2007), "Interatomic potential for Si-O systems using Tersoff parameterization", Computational Materials Science, 39(2), 334-339. DOI: 10.1016/j.commatsci.2006.06.010.
Abstract: A parameter set for Tersoff potential has been developed to investigate the structural properties of Si-O systems. The potential parameters have been determined based on ab initio calculations of small molecules and the experimental data of α-quartz. The structural properties of various silica polymorphs calculated by using the new potential were in good agreement with their experimental data and ab initio calculation results. Furthermore, we have prepared SiO2 glass using molecular dynamics (MD) simulations by rapid quenching of melted SiO2. The radial distribution function and phonon density of states of SiO2 glass generated by MD simulation were in excellent agreement with those of SiO2 glass obtained experimentally.

LAMMPS pair_style tersoff (2007--Munetoh-S--Si-O--LAMMPS--ipr1)
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Notes: This file was created and verified by Lucas Hale. The parameter values are comparable to the SiO.tersoff file in the August 22, 2018 LAMMPS distribution, with this file having higher numerical precision for the derived mixing parameters.
File(s):
Citation: J.Q. Broughton, C.A. Meli, P. Vashishta, and R.K. Kalia (1997), "Direct atomistic simulation of quartz crystal oscillators: Bulk properties and nanoscale devices", Physical Review B, 56(2), 611-618. DOI: 10.1103/physrevb.56.611.
Abstract: Current experimental research aims to reduce the size of quartz crystal oscillators into the submicrometer range. Devices then comprise multimillion atoms and operating frequencies will be in the gigahertz regime. Such characteristics make direct atomic scale simulation feasible using large scale parallel computing. Here, we describe molecular-dynamics simulations on bulk and nanoscale device systems focusing on elastic constants and flexural frequencies. Here we find (a) in order to achieve elastic constants within 1% of those of the bulk requires approximately one million atoms; precisely the experimental regime of interest; (b) differences from continuum mechanical frequency predictions are observable for 17 nm devices; (c) devices with 1% defects exhibit dramatic anharmonicity. A subsequent paper describes the direct atomistic simulation of operating characteristics of a micrometer scale device. A PAPS cosubmission gives algorithmic details.

LAMMPS pair_style vashishta (1997--Broughton-J-Q--Si-O--LAMMPS--ipr1)
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Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
File(s):
Citation: A. Nakano, R.K. Kalia, and P. Vashishta (1994), "First sharp diffraction peak and intermediate-range order in amorphous silica: finite-size effects in molecular dynamics simulations", Journal of Non-Crystalline Solids, 171(2), 157-163. DOI: 10.1016/0022-3093(94)90351-4.
Abstract: Large-scale molecular dynamics simulations of amorphous silica are carried out on systems containing up to 41472 particles using an effective interatomic potential consisting of two-body and three-body covalent interactions. The intermediate-range order represented by the first sharp diffraction peak (FSDP) in the neutron static structure factor shows a significant dependence on the system size. Correlations in the range 0.4–1.1 nm are found to play a vital role in determining the shape of the FSDP correctly. The calculated structure factor for the largest system is in excellent agreement with neutron diffraction experiments, including the height of the FSDP.

LAMMPS pair_style vashishta (1994--Nakano-A--Si-O--LAMMPS--ipr1)
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Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
File(s):
Citation: P. Vashishta, R.K. Kalia, J.P. Rino, and I. Ebbsjö (1990), "Interaction potential for SiO2: A molecular-dynamics study of structural correlations", Physical Review B, 41(17), 12197-12209. DOI: 10.1103/physrevb.41.12197.
Abstract: An interaction potential consisting of two-body and three-body covalent interactions is proposed for SiO2. The interaction potential is used in molecular-dynamics studies of structural and dynamical correlations of crystalline, molten, and vitreous states under various conditions of densities and temperatures. The two-body contribution to the interaction potential consists of steric repulsion due to atomic sizes, Coulomb interactions resulting from charge transfer, and charge-dipole interaction to include the effects of large electronic polarizability of anions. The three-body covalent contributions include O-Si-O and Si-O-Si interactions which are angle dependent and functions of Si-O distance. In lattice-structure calculations with the total potential function, α-cristobalite and α-quartz are found to have the lowest and almost degenerate energies, in agreement with experiments. The energies for β-cristobalite, β-quartz, and keatite are found to be higher than those for α-cristobalite and α-quartz. Molecular-dynamics calculations with this potential function correctly describe the short- and intermediate-range order in molten and vitreous states.\nIn the latter, partial pair-distribution functions give Si-O, O-O, and Si-Si bond lengths of 1.62, 2.65, and 3.05 Å, respectively. The vitreous state consists of nearly ideal Si(O1/2)4 tetrahedra in corner-sharing configurations. The Si-O-Si bond-angle distribution has a peak at 142° and a full width at half maximum (FWHM) of 25° in good agreement with nuclear magnetic resonance experiments. The calculated static structure factor is also in agreement with neutron-diffraction experiments. Partial static structure factors reveal that intermediate-range Si-Si, O-O, and Si-O correlations between 4 and 8 Å give rise to the first sharp diffraction peak (FSDP). The FSDP is absent in charge-charge structure factor, which indicates that charge neutrality prevails over length scales between 4 and 8 Å. Dynamical correlations in vitreous and molten states, phonon densities of states of crystalline and vitreous SiO2, infrared spectra of crystalline, vitreous and molten states, isotope effect, distribution of rings and their structure in molten and vitreous states, and structural transformations at high pressures will be discussed in subsequent papers.

LAMMPS pair_style vashishta (1990--Vashishta-P--Si-O--LAMMPS--ipr1)
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Notes: This file was taken from the August 22, 2018 LAMMPS distribution.
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Date Created: October 5, 2010 | Last updated: November 08, 2022