diff --git a/src/pair_wf.cpp b/src/pair_wf.cpp
new file mode 100644
index 0000000000..00f3ad5aba
--- /dev/null
+++ b/src/pair_wf.cpp
@@ -0,0 +1,403 @@
+/* ----------------------------------------------------------------------
+   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.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing Authors: Xipeng Wang, Simon Ramirez-Hinestrosa
+------------------------------------------------------------------------- */
+
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include "pair_wf.h"
+#include "atom.h"
+#include "comm.h"
+#include "force.h"
+#include "neigh_list.h"
+#include "math_const.h"
+#include "memory.h"
+#include "error.h"
+
+using namespace LAMMPS_NS;
+using namespace MathConst;
+
+/* ---------------------------------------------------------------------- */
+
+PairWF::PairWF(LAMMPS *lmp) : Pair(lmp)
+{
+  writedata = 1;
+}
+
+/* ---------------------------------------------------------------------- */
+
+PairWF::~PairWF()
+{
+  if (allocated) {
+    memory->destroy(setflag);
+    memory->destroy(cutsq);
+    memory->destroy(cut);
+    memory->destroy(epsilon);
+    memory->destroy(sigma);
+    memory->destroy(nu);
+    memory->destroy(mu);
+    memory->destroy(nm);
+    memory->destroy(e0nm);  //Alpha * epsilon
+    memory->destroy(rcmu);
+    memory->destroy(sigma_mu);
+    memory->destroy(offset);
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void PairWF::compute(int eflag, int vflag)
+{
+  int i,j,ii,jj,inum,jnum,itype,jtype;
+  double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
+  double rsq,r2inv,factor_lj;
+  double r,forcenm,rminv, rm, rn;
+  int *ilist,*jlist,*numneigh,**firstneigh;
+
+  evdwl = 0.0;
+  if (eflag || vflag) ev_setup(eflag,vflag);
+  else evflag = vflag_fdotr = 0;
+
+  double **x = atom->x;
+  double **f = atom->f;
+  int *type = atom->type;
+  int nlocal = atom->nlocal;
+  double *special_lj = force->special_lj;
+  int newton_pair = force->newton_pair;
+
+  inum = list->inum;
+  ilist = list->ilist;
+  numneigh = list->numneigh;
+  firstneigh = list->firstneigh;
+
+  // loop over neighbors of my atoms
+
+  for (ii = 0; ii < inum; ii++) {
+    i = ilist[ii];
+    xtmp = x[i][0];
+    ytmp = x[i][1];
+    ztmp = x[i][2];
+    itype = type[i];
+    jlist = firstneigh[i];
+    jnum = numneigh[i];
+
+    for (jj = 0; jj < jnum; jj++) {
+      j = jlist[jj];
+      factor_lj = special_lj[sbmask(j)];
+      j &= NEIGHMASK;
+
+      delx = xtmp - x[j][0];
+      dely = ytmp - x[j][1];
+      delz = ztmp - x[j][2];
+      rsq = delx*delx + dely*dely + delz*delz;
+      jtype = type[j];
+
+      if (rsq < cutsq[itype][jtype]) {
+        r2inv = 1.0/rsq;
+        r = sqrt(rsq);
+        rminv = pow(r2inv,mu[itype][jtype]);
+        rm = sigma_mu[itype][jtype]*rminv - 1.0;
+        rn = rcmu[itype][jtype]*rminv - 1.0;
+
+        forcenm = 2.0*mu[itype][jtype] *sigma_mu[itype][jtype]*pow(rn,2.0*nu[itype][jtype])
+                + 4.0*nm[itype][jtype] *rcmu[itype][jtype]*rm*pow(rn,2.0*nu[itype][jtype]-1.0);
+        fpair = factor_lj*e0nm[itype][jtype]*forcenm*pow(r2inv,mu[itype][jtype]+1.0);
+
+        f[i][0] += delx*fpair;
+        f[i][1] += dely*fpair;
+        f[i][2] += delz*fpair;
+        if (newton_pair || j < nlocal) {
+          f[j][0] -= delx*fpair;
+          f[j][1] -= dely*fpair;
+          f[j][2] -= delz*fpair;
+        }
+
+        if (eflag) {
+          evdwl = e0nm[itype][jtype] *
+            (rm*pow(rn,2.0*nu[itype][jtype])) - offset[itype][jtype];
+          evdwl *= factor_lj;
+        }
+
+        if (evflag) ev_tally(i,j,nlocal,newton_pair,
+                             evdwl,0.0,fpair,delx,dely,delz);
+      }
+    }
+  }
+
+  if (vflag_fdotr) virial_fdotr_compute();
+}
+
+/* ----------------------------------------------------------------------
+   allocate all arrays
+------------------------------------------------------------------------- */
+
+void PairWF::allocate()
+{
+  allocated = 1;
+  int n = atom->ntypes;
+
+  memory->create(setflag,n+1,n+1,"pair:setflag");
+  for (int i = 1; i <= n; i++)
+    for (int j = i; j <= n; j++)
+      setflag[i][j] = 0;
+
+  memory->create(cutsq,n+1,n+1,"pair:cutsq");
+
+  memory->create(cut,n+1,n+1,"pair:cut");
+  memory->create(epsilon,n+1,n+1,"pair:epsilon");
+  memory->create(sigma,n+1,n+1,"pair:sigma");
+  memory->create(nu,n+1,n+1,"pair:nu");
+  memory->create(mu,n+1,n+1,"pair:mu");
+  memory->create(nm,n+1,n+1,"pair:nm");
+  memory->create(e0nm,n+1,n+1,"pair:e0nm");
+  memory->create(rcmu,n+1,n+1,"pair:rcmu");
+  memory->create(sigma_mu,n+1,n+1,"pair:sigma_mu");
+  memory->create(offset,n+1,n+1,"pair:offset");
+}
+
+/* ----------------------------------------------------------------------
+   global settings
+------------------------------------------------------------------------- */
+
+void PairWF::settings(int narg, char **arg)
+{
+  if (narg != 1) error->all(FLERR,"Illegal pair_style command");
+
+  cut_global = force->numeric(FLERR,arg[0]);
+
+  // reset cutoffs that have been explicitly set
+
+  if (allocated) {
+    int i,j;
+    for (i = 1; i <= atom->ntypes; i++)
+      for (j = i; j <= atom->ntypes; j++)
+        if (setflag[i][j]) cut[i][j] = cut_global;
+  }
+}
+
+/* ----------------------------------------------------------------------
+   set coeffs for one or more type pairs
+------------------------------------------------------------------------- */
+
+void PairWF::coeff(int narg, char **arg)
+{
+  if (narg < 6 || narg > 7)
+    error->all(FLERR,"Incorrect args for pair coefficients");
+  if (!allocated) allocate();
+
+  int ilo,ihi,jlo,jhi;
+  force->bounds(FLERR,arg[0],atom->ntypes,ilo,ihi);
+  force->bounds(FLERR,arg[1],atom->ntypes,jlo,jhi);
+
+  double epsilon_one = force->numeric(FLERR,arg[2]);
+  double sigma_one = force->numeric(FLERR,arg[3]);
+  double nu_one = force->numeric(FLERR,arg[4]);
+  double mu_one = force->numeric(FLERR,arg[5]);
+
+  double cut_one = cut_global;
+  if (narg == 7) cut_one = force->numeric(FLERR,arg[6]);
+
+  int count = 0;
+  for (int i = ilo; i <= ihi; i++) {
+    for (int j = MAX(jlo,i); j <= jhi; j++) {
+      epsilon[i][j] = epsilon_one;
+      sigma[i][j] = sigma_one;
+      nu[i][j] = nu_one;
+      mu[i][j] = mu_one;
+      cut[i][j] = cut_one;
+      setflag[i][j] = 1;
+      count++;
+    }
+  }
+
+  if (count == 0) error->all(FLERR,"Incorrect args for pair coefficients");
+}
+
+/* ----------------------------------------------------------------------
+   init for one type pair i,j and corresponding j,i
+------------------------------------------------------------------------- */
+
+double PairWF::init_one(int i, int j)
+{
+  if (setflag[i][j] == 0) error->all(FLERR,"All pair coeffs are not set");
+
+  nm[i][j] = nu[i][j]*mu[i][j];
+  e0nm[i][j] = epsilon[i][j]*2.0*nu[i][j]*pow(cut[i][j]/sigma[i][j],2.0*mu[i][j])
+                       *pow((1+2.0*nu[i][j])/(2.0*nu[i][j])/(pow(cut[i][j]/sigma[i][j],2.0*mu[i][j])-1.0),
+                              2.0*nu[i][j]+1.0);
+  rcmu[i][j] = pow(cut[i][j],2.0*mu[i][j]);
+  sigma_mu[i][j] = pow(sigma[i][j], 2.0*mu[i][j]);
+
+  if (offset_flag && (cut[i][j] > 0.0)) {
+    offset[i][j] = 0.0;
+  } else offset[i][j] = 0.0;
+
+  epsilon[j][i] = epsilon[i][j];
+  nu[j][i] = nu[i][j];
+  mu[j][i] = mu[i][j];
+  nm[j][i] = nm[i][j];
+  sigma[j][i] = sigma[i][j];
+  e0nm[j][i] = e0nm[i][j];
+  rcmu[j][i] = rcmu[i][j];
+  sigma_mu[j][i] = sigma_mu[i][j];
+  offset[j][i] = offset[i][j];
+
+  return cut[i][j];
+}
+
+/* ----------------------------------------------------------------------
+  proc 0 writes to restart file
+------------------------------------------------------------------------- */
+
+void PairWF::write_restart(FILE *fp)
+{
+  write_restart_settings(fp);
+
+  int i,j;
+  for (i = 1; i <= atom->ntypes; i++)
+    for (j = i; j <= atom->ntypes; j++) {
+      fwrite(&setflag[i][j],sizeof(int),1,fp);
+      if (setflag[i][j]) {
+        fwrite(&epsilon[i][j],sizeof(double),1,fp);
+        fwrite(&sigma[i][j],sizeof(double),1,fp);
+        fwrite(&nu[i][j],sizeof(double),1,fp);
+        fwrite(&mu[i][j],sizeof(double),1,fp);
+        fwrite(&cut[i][j],sizeof(double),1,fp);
+      }
+    }
+}
+
+/* ----------------------------------------------------------------------
+  proc 0 reads from restart file, bcasts
+------------------------------------------------------------------------- */
+
+void PairWF::read_restart(FILE *fp)
+{
+  read_restart_settings(fp);
+  allocate();
+
+  int i,j;
+  int me = comm->me;
+  for (i = 1; i <= atom->ntypes; i++)
+    for (j = i; j <= atom->ntypes; j++) {
+      if (me == 0) fread(&setflag[i][j],sizeof(int),1,fp);
+      MPI_Bcast(&setflag[i][j],1,MPI_INT,0,world);
+      if (setflag[i][j]) {
+        if (me == 0) {
+          fread(&epsilon[i][j],sizeof(double),1,fp);
+          fread(&sigma[i][j],sizeof(double),1,fp);
+          fread(&nu[i][j],sizeof(double),1,fp);
+          fread(&mu[i][j],sizeof(double),1,fp);
+          fread(&cut[i][j],sizeof(double),1,fp);
+        }
+        MPI_Bcast(&epsilon[i][j],1,MPI_DOUBLE,0,world);
+        MPI_Bcast(&sigma[i][j],1,MPI_DOUBLE,0,world);
+        MPI_Bcast(&nu[i][j],1,MPI_DOUBLE,0,world);
+        MPI_Bcast(&mu[i][j],1,MPI_DOUBLE,0,world);
+        MPI_Bcast(&cut[i][j],1,MPI_DOUBLE,0,world);
+      }
+    }
+}
+
+/* ----------------------------------------------------------------------
+  proc 0 writes to restart file
+------------------------------------------------------------------------- */
+
+void PairWF::write_restart_settings(FILE *fp)
+{
+  fwrite(&cut_global,sizeof(double),1,fp);
+  fwrite(&offset_flag,sizeof(int),1,fp);
+  fwrite(&mix_flag,sizeof(int),1,fp);
+//  fwrite(&tail_flag,sizeof(int),1,fp);
+}
+
+/* ----------------------------------------------------------------------
+  proc 0 reads from restart file, bcasts
+------------------------------------------------------------------------- */
+
+void PairWF::read_restart_settings(FILE *fp)
+{
+  if (comm->me == 0) {
+    fread(&cut_global,sizeof(double),1,fp);
+    fread(&offset_flag,sizeof(int),1,fp);
+    fread(&mix_flag,sizeof(int),1,fp);
+//    fread(&tail_flag,sizeof(int),1,fp);
+  }
+  MPI_Bcast(&cut_global,1,MPI_DOUBLE,0,world);
+  MPI_Bcast(&offset_flag,1,MPI_INT,0,world);
+  MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
+//  MPI_Bcast(&tail_flag,1,MPI_INT,0,world);
+}
+
+/* ----------------------------------------------------------------------
+   proc 0 writes to data file
+------------------------------------------------------------------------- */
+
+void PairWF::write_data(FILE *fp)
+{
+  for (int i = 1; i <= atom->ntypes; i++)
+    fprintf(fp,"%d %g %g %g %g\n",i,epsilon[i][i],sigma[i][i],nu[i][i],mu[i][i]);
+}
+
+/* ----------------------------------------------------------------------
+   proc 0 writes all pairs to data file
+------------------------------------------------------------------------- */
+
+void PairWF::write_data_all(FILE *fp)
+{
+  for (int i = 1; i <= atom->ntypes; i++)
+    for (int j = i; j <= atom->ntypes; j++)
+      fprintf(fp,"%d %d %g %g %g %g %g\n",i,j,
+              epsilon[i][j],sigma[i][j],nu[i][j],mu[i][j],cut[i][j]);
+}
+
+/* ---------------------------------------------------------------------- */
+
+double PairWF::single(int /*i*/, int /*j*/, int itype, int jtype,
+                      double rsq, double /*factor_coul*/, double factor_lj,
+                      double &fforce)
+{
+  double r2inv,r, rminv, rm, rn, forcenm,phinm;
+
+  r2inv = 1.0/rsq;
+  r = sqrt(rsq);
+   
+  r2inv = 1.0/rsq;
+  r = sqrt(rsq);
+  rminv = pow(r2inv,mu[itype][jtype]);
+  rm = sigma_mu[itype][jtype]*rminv - 1.0;
+  rn = rcmu[itype][jtype]*rminv - 1.0;
+  forcenm = 2.0*mu[itype][jtype] *sigma_mu[itype][jtype]*pow(rn,2.0*nu[itype][jtype])
+                + 4.0*nm[itype][jtype] *rcmu[itype][jtype]*rm*pow(rn,2.0*nu[itype][jtype]-1.0);
+  fforce = factor_lj*e0nm[itype][jtype]*forcenm*pow(r2inv,mu[itype][jtype]+1.0);
+
+  phinm = e0nm[itype][jtype] * rm*pow(rn,2.0*nu[itype][jtype]) -
+    offset[itype][jtype];
+  return factor_lj*phinm;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void *PairWF::extract(const char *str, int &dim)
+{
+  dim = 2;
+  if (strcmp(str,"epsilon") == 0) return (void *) epsilon;
+  if (strcmp(str,"sigma") == 0) return (void *) sigma;
+  if (strcmp(str,"nu") == 0) return (void *) nu;
+  if (strcmp(str,"mu") == 0) return (void *) mu;
+  return NULL;
+}
diff --git a/src/pair_wf.h b/src/pair_wf.h
new file mode 100644
index 0000000000..e4254f4ccf
--- /dev/null
+++ b/src/pair_wf.h
@@ -0,0 +1,76 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   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.
+------------------------------------------------------------------------- */
+
+#ifdef PAIR_CLASS
+
+PairStyle(wf,PairWF)
+
+#else
+
+#ifndef LMP_PAIR_WF
+#define LMP_PAIR_WF
+
+#include "pair.h"
+
+namespace LAMMPS_NS {
+
+class PairWF : public Pair {
+ public:
+  PairWF(class LAMMPS *);
+  virtual ~PairWF();
+
+  virtual void compute(int, int);
+  void settings(int, char **);
+  void coeff(int, char **);
+  double init_one(int, int);
+  void write_restart(FILE *);
+  void read_restart(FILE *);
+  void write_restart_settings(FILE *);
+  void read_restart_settings(FILE *);
+  void write_data(FILE *);
+  void write_data_all(FILE *);
+  double single(int, int, int, int, double, double, double, double &);
+  void *extract(const char *, int &);
+
+ protected:
+  double cut_global;
+  double **cut;
+  double **epsilon,**sigma,**nu, **mu;
+  double **nm,**e0nm,**rcmu,**sigma_mu,**offset;
+
+  void allocate();
+};
+
+}
+
+#endif
+#endif
+
+/* ERROR/WARNING messages:
+
+E: Illegal ... command
+
+Self-explanatory.  Check the input script syntax and compare to the
+documentation for the command.  You can use -echo screen as a
+command-line option when running LAMMPS to see the offending line.
+
+E: Incorrect args for pair coefficients
+
+Self-explanatory.  Check the input script or data file.
+
+E: All pair coeffs are not set
+
+All pair coefficients must be set in the data file or by the
+pair_coeff command before running a simulation.
+
+*/