git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@26 f3b2605a-c512-4ea7-a41b-209d697bcdaa

2006-09-27 19:51:33 +00:00
parent 3422cb245c
commit 222c95507e
536 changed files with 108384 additions and 0 deletions
--- a/src/fix_drag.cpp
+++ b/src/fix_drag.cpp
@ -0,0 +1,112 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   www.cs.sandia.gov/~sjplimp/lammps.html
+   Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under 
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#include "math.h"
+#include "stdlib.h"
+#include "string.h"
+#include "fix_drag.h"
+#include "atom.h"
+#include "update.h"
+#include "respa.h"
+#include "domain.h"
+#include "error.h"
+
+/* ---------------------------------------------------------------------- */
+
+FixDrag::FixDrag(int narg, char **arg) : Fix(narg, arg)
+{
+  if (narg != 8) error->all("Illegal fix drag command");
+
+  xflag = yflag = zflag = 1;
+
+  if (strcmp(arg[3],"NULL") == 0) xflag = 0;
+  else xc = atof(arg[3]);
+  if (strcmp(arg[4],"NULL") == 0) yflag = 0;
+  else yc = atof(arg[4]);
+  if (strcmp(arg[5],"NULL") == 0) zflag = 0;
+  else zc = atof(arg[5]);
+
+  f_mag = atof(arg[6]);
+  delta = atof(arg[7]);
+}
+
+/* ---------------------------------------------------------------------- */
+
+int FixDrag::setmask()
+{
+  int mask = 0;
+  mask |= POST_FORCE;
+  mask |= POST_FORCE_RESPA;
+  return mask;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixDrag::init()
+{
+  if (strcmp(update->integrate_style,"respa") == 0)
+    nlevels_respa = ((Respa *) update->integrate)->nlevels;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixDrag::setup()
+{
+  if (strcmp(update->integrate_style,"verlet") == 0)
+    post_force(1);
+  else {
+    ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
+    post_force_respa(1,nlevels_respa-1,0);
+    ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixDrag::post_force(int vflag)
+{
+  // apply drag force to atoms in group of magnitude f_mag
+  // apply in direction (r-r0) if atom is further than delta away
+
+  double **x = atom->x;
+  double **f = atom->f;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+  
+  double dx,dy,dz,r,prefactor;
+
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+      dx = x[i][0] - xc;
+      dy = x[i][1] - yc;
+      dz = x[i][2] - zc;
+      if (!xflag) dx = 0.0;
+      if (!yflag) dy = 0.0;
+      if (!zflag) dz = 0.0;
+      domain->minimum_image(&dx,&dy,&dz);
+      r = sqrt(dx*dx + dy*dy + dz*dz);
+      if (r > delta) {
+	prefactor = f_mag/r;
+	f[i][0] -= prefactor*dx;
+	f[i][1] -= prefactor*dy;
+	f[i][2] -= prefactor*dz;
+      }
+    }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixDrag::post_force_respa(int vflag, int ilevel, int iloop)
+{
+  if (ilevel == nlevels_respa-1) post_force(vflag);
+}