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# Copyright (c) 2012, Regents of the University of Minnesota.  All rights reserved.
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# Contributors:
#    Ryan S. Elliott
#    Ellad B. Tadmor
#    Valeriu Smirichinski
#    Amit Singh
#    Mingjian Wen


This directory (Three_Body_Stillinger_Weber_Zhang_Silicene_Model2_Si__MO_475612090600_002)
contains a parameterization of the Stillinger-Weber potential [1] optimized for 
Silicene (single-layer Si sheets) [2] based on the KIM Model Driver 
Three_Body_Stillinger_Weber.  According to the authors, the potential
"accurately reproduces the low buckling structure of silicene and the full phonon dispersion curves obtained from ab initio calculations" [2]. 
The authors provide two sets of parameters. This parameterization corresponds 
to the parameter set referred to as "Optimized SW2" in [2].

The following files are in this directory:

Three_Body_Stillinger_Weber_Zhang_Silicene_Model2_Si.params

  first line: 1 (number of species)

  Then the following 9 parameters:
  A(in ev) B p q sigma(in Angstrom) lambda(in eV) gamma(in Angstorm) costheta_0 cutoff

  Any additional lines will be silently ignored.


LICENSE.CDDL
  The Common Development and Distribution License (CDDL) Version 1.0 file

Makefile
  makefile to compile and build the Model based on the specified KIM Model Driver

README
  This file

References:

1. F. H. Stillinger and T. A. Weber, "Computer simulation of local order in condensed phases of silicon", Phys. Rev. B, vol. 31, 5262-5271, 1985

2. X. Zhang, H. Xie, M. Hu, H. Bao, S. Yue, G. Qin and G. Su, "Thermal conductivity of silicene calculated using an optimized Stillinger-Weber potential", Phys. Rev. B, vol 89, 054310, 2014.



###############################################################################
The functional form of the SW potential is rewritten as:

  E = sum_{i,j>i} phi_2(rij) + sum_{i, j!=i, k>j} phi_3(rij, rik, theta)

  phi_2(rij)           = Aij*(Bij(rij/sigma_ij)^(-p) - (rij/sigma_ij)^(-q))
                         * exp(sigma_ij/(rij - rcutij))

  phi_3(rij,rik,theta) = lambda_ijk(cos[theta] - cos[theta0])^2
                         *  exp(gamma_ij/(rij - rcutij) + gamma_ik/(rik - rcutik))
  
Compared to the standard SW potential, the following redefinitions have been made:
  A      := A*epsilon
  lambda := lambda*epsilon
  gamma  := gamma*sigma
  rcut   := a*sigma