forked from lijiext/lammps
150 lines
4.0 KiB
C++
150 lines
4.0 KiB
C++
/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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http://lammps.sandia.gov, Sandia National Laboratories
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Steve Plimpton, sjplimp@sandia.gov
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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 "math.h"
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#include "stdlib.h"
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#include "string.h"
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#include "fix_drag.h"
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#include "atom.h"
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#include "update.h"
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#include "respa.h"
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#include "domain.h"
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#include "error.h"
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#include "force.h"
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using namespace LAMMPS_NS;
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using namespace FixConst;
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/* ---------------------------------------------------------------------- */
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FixDrag::FixDrag(LAMMPS *lmp, int narg, char **arg) :
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Fix(lmp, narg, arg)
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{
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if (narg != 8) error->all(FLERR,"Illegal fix drag command");
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vector_flag = 1;
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size_vector = 3;
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global_freq = 1;
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extvector = 1;
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xflag = yflag = zflag = 1;
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if (strcmp(arg[3],"NULL") == 0) xflag = 0;
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else xc = force->numeric(FLERR,arg[3]);
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if (strcmp(arg[4],"NULL") == 0) yflag = 0;
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else yc = force->numeric(FLERR,arg[4]);
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if (strcmp(arg[5],"NULL") == 0) zflag = 0;
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else zc = force->numeric(FLERR,arg[5]);
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f_mag = force->numeric(FLERR,arg[6]);
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delta = force->numeric(FLERR,arg[7]);
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force_flag = 0;
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ftotal[0] = ftotal[1] = ftotal[2] = 0.0;
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}
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/* ---------------------------------------------------------------------- */
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int FixDrag::setmask()
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{
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int mask = 0;
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mask |= POST_FORCE;
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mask |= POST_FORCE_RESPA;
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return mask;
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}
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/* ---------------------------------------------------------------------- */
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void FixDrag::init()
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{
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if (strstr(update->integrate_style,"respa"))
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nlevels_respa = ((Respa *) update->integrate)->nlevels;
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}
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/* ---------------------------------------------------------------------- */
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void FixDrag::setup(int vflag)
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{
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if (strstr(update->integrate_style,"verlet"))
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post_force(vflag);
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else {
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((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
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post_force_respa(vflag,nlevels_respa-1,0);
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((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
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}
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}
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/* ---------------------------------------------------------------------- */
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void FixDrag::post_force(int vflag)
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{
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// apply drag force to atoms in group of magnitude f_mag
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// apply in direction (r-r0) if atom is further than delta away
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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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ftotal[0] = ftotal[1] = ftotal[2] = 0.0;
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force_flag = 0;
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double dx,dy,dz,r,prefactor,fx,fy,fz;
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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dx = x[i][0] - xc;
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dy = x[i][1] - yc;
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dz = x[i][2] - zc;
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if (!xflag) dx = 0.0;
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if (!yflag) dy = 0.0;
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if (!zflag) dz = 0.0;
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domain->minimum_image(dx,dy,dz);
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r = sqrt(dx*dx + dy*dy + dz*dz);
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if (r > delta) {
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prefactor = f_mag/r;
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fx = prefactor*dx;
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fy = prefactor*dy;
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fz = prefactor*dz;
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f[i][0] -= fx;
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f[i][1] -= fy;
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f[i][2] -= fz;
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ftotal[0] -= fx;
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ftotal[1] -= fy;
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ftotal[2] -= fz;
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}
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}
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}
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/* ---------------------------------------------------------------------- */
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void FixDrag::post_force_respa(int vflag, int ilevel, int iloop)
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{
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if (ilevel == nlevels_respa-1) post_force(vflag);
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}
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/* ----------------------------------------------------------------------
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return components of total drag force on fix group
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------------------------------------------------------------------------- */
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double FixDrag::compute_vector(int n)
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{
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// only sum across procs one time
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if (force_flag == 0) {
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MPI_Allreduce(ftotal,ftotal_all,3,MPI_DOUBLE,MPI_SUM,world);
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force_flag = 1;
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}
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return ftotal_all[n];
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}
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