97 lines
2.8 KiB
C++
97 lines
2.8 KiB
C++
/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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https://www.lammps.org/, Sandia National Laboratories
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LAMMPS development team: developers@lammps.org
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Copyright (2003) Sandia Corporation. Under the terms of Contract
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DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
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certain rights in this software. This software is distributed under
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the GNU General Public License.
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See the README file in the top-level LAMMPS directory.
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------------------------------------------------------------------------- */
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#include "fix_wall_lj126.h"
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#include "atom.h"
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#include "error.h"
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#include "math_special.h"
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using namespace LAMMPS_NS;
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using MathSpecial::powint;
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/* ---------------------------------------------------------------------- */
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FixWallLJ126::FixWallLJ126(LAMMPS *lmp, int narg, char **arg) : FixWall(lmp, narg, arg)
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{
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dynamic_group_allow = 1;
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}
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/* ---------------------------------------------------------------------- */
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void FixWallLJ126::precompute(int m)
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{
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coeff1[m] = 48.0 * epsilon[m] * powint(sigma[m], 12);
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coeff2[m] = 24.0 * epsilon[m] * powint(sigma[m], 6);
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coeff3[m] = 4.0 * epsilon[m] * powint(sigma[m], 12);
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coeff4[m] = 4.0 * epsilon[m] * powint(sigma[m], 6);
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double r2inv = 1.0 / (cutoff[m] * cutoff[m]);
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double r6inv = r2inv * r2inv * r2inv;
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offset[m] = r6inv * (coeff3[m] * r6inv - coeff4[m]);
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}
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/* ----------------------------------------------------------------------
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interaction of all particles in group with a wall
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m = index of wall coeffs
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which = xlo,xhi,ylo,yhi,zlo,zhi
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error if any particle is on or behind wall
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------------------------------------------------------------------------- */
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void FixWallLJ126::wall_particle(int m, int which, double coord)
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{
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double delta, rinv, r2inv, r6inv, fwall;
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double vn;
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double **x = atom->x;
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double **f = atom->f;
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int *mask = atom->mask;
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int nlocal = atom->nlocal;
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int dim = which / 2;
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int side = which % 2;
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if (side == 0) side = -1;
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int onflag = 0;
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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if (side < 0)
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delta = x[i][dim] - coord;
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else
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delta = coord - x[i][dim];
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if (delta >= cutoff[m]) continue;
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if (delta <= 0.0) {
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onflag = 1;
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continue;
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}
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rinv = 1.0 / delta;
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r2inv = rinv * rinv;
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r6inv = r2inv * r2inv * r2inv;
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fwall = side * r6inv * (coeff1[m] * r6inv - coeff2[m]) * rinv;
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f[i][dim] -= fwall;
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ewall[0] += r6inv * (coeff3[m] * r6inv - coeff4[m]) - offset[m];
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ewall[m + 1] += fwall;
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if (evflag) {
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if (side < 0)
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vn = -fwall * delta;
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else
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vn = fwall * delta;
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v_tally(dim, i, vn);
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}
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}
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if (onflag) error->one(FLERR, "Particle on or inside fix wall surface");
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}
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