From 5028d01a487d33a4ce4198ffad2b21ff36d7bb81 Mon Sep 17 00:00:00 2001
From: sjplimp <sjplimp@f3b2605a-c512-4ea7-a41b-209d697bcdaa>
Date: Thu, 22 Mar 2007 17:06:11 +0000
Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@432
 f3b2605a-c512-4ea7-a41b-209d697bcdaa

---
 src/fix_nve_noforce.cpp | 79 +++++++++++++++++++++++++++++++++++++++++
 src/fix_nve_noforce.h   | 36 +++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 src/fix_nve_noforce.cpp
 create mode 100644 src/fix_nve_noforce.h

diff --git a/src/fix_nve_noforce.cpp b/src/fix_nve_noforce.cpp
new file mode 100644
index 0000000000..7e0f55b69e
--- /dev/null
+++ b/src/fix_nve_noforce.cpp
@@ -0,0 +1,79 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   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 "stdio.h"
+#include "string.h"
+#include "fix_nve_noforce.h"
+#include "atom.h"
+#include "update.h"
+#include "respa.h"
+#include "error.h"
+
+using namespace LAMMPS_NS;
+
+/* ---------------------------------------------------------------------- */
+
+FixNVENoforce::FixNVENoforce(LAMMPS *lmp, int narg, char **arg) :
+  Fix(lmp, narg, arg)
+{
+  if (narg != 3) error->all("Illegal fix nve/noforce command");
+}
+
+/* ---------------------------------------------------------------------- */
+
+int FixNVENoforce::setmask()
+{
+  int mask = 0;
+  mask |= INITIAL_INTEGRATE;
+  mask |= INITIAL_INTEGRATE_RESPA;
+  return mask;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixNVENoforce::init()
+{
+  dtv = update->dt;
+
+  if (strcmp(update->integrate_style,"respa") == 0)
+    step_respa = ((Respa *) update->integrate)->step;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixNVENoforce::initial_integrate()
+{
+  double **x = atom->x;
+  double **v = atom->v;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+
+  for (int i = 0; i < nlocal; i++) {
+    if (mask[i] & groupbit) {
+      x[i][0] += dtv * v[i][0];
+      x[i][1] += dtv * v[i][1];
+      x[i][2] += dtv * v[i][2];
+    }
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixNVENoforce::initial_integrate_respa(int ilevel, int flag)
+{
+  if (flag) return;             // only used by NPT,NPH
+
+  dtv = step_respa[ilevel];
+
+  if (ilevel == 0) initial_integrate();
+}
diff --git a/src/fix_nve_noforce.h b/src/fix_nve_noforce.h
new file mode 100644
index 0000000000..b24554d5de
--- /dev/null
+++ b/src/fix_nve_noforce.h
@@ -0,0 +1,36 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   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.
+------------------------------------------------------------------------- */
+
+#ifndef FIX_NVE_NOFORCE_H
+#define FIX_NVE_NOFORCE_H
+
+#include "fix.h"
+
+namespace LAMMPS_NS {
+
+class FixNVENoforce : public Fix {
+ public:
+  FixNVENoforce(class LAMMPS *, int, char **);
+  int setmask();
+  void init();
+  void initial_integrate();
+  void initial_integrate_respa(int, int);
+
+ private:
+  double dtv;
+  double *step_respa;
+};
+
+}
+
+#endif