diff --git a/src/MC/fix_gcmc.cpp b/src/MC/fix_gcmc.cpp
index d13135b8a..2deeb56c6 100644
--- a/src/MC/fix_gcmc.cpp
+++ b/src/MC/fix_gcmc.cpp
@@ -1,1303 +1,1310 @@
 /* ----------------------------------------------------------------------
    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 author: Paul Crozier (SNL)
 ------------------------------------------------------------------------- */
 
 #include "math.h"
 #include "stdlib.h"
 #include "string.h"
 #include "fix_gcmc.h"
 #include "atom.h"
 #include "atom_vec.h"
 #include "atom_vec_hybrid.h"
 #include "update.h"
 #include "modify.h"
 #include "fix.h"
 #include "comm.h"
 #include "group.h"
 #include "domain.h"
 #include "region.h"
 #include "random_park.h"
 #include "force.h"
 #include "pair.h"
 #include "math_const.h"
 #include "memory.h"
 #include "error.h"
 #include <iostream>
 
 using namespace std;
 using namespace LAMMPS_NS;
 using namespace FixConst;
 using namespace MathConst;
 
 /* ---------------------------------------------------------------------- */
 
 FixGCMC::FixGCMC(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg)
 {
   if (narg < 11) error->all(FLERR,"Illegal fix gcmc command");
 
   vector_flag = 1;
   size_vector = 8;
   global_freq = 1;
   extvector = 0;
   restart_global = 1;
   time_depend = 1;
 
   // required args
 
   nevery = atoi(arg[3]);
   nexchanges = atoi(arg[4]);
   nmcmoves = atoi(arg[5]);
   ngcmc_type = atoi(arg[6]);
   seed = atoi(arg[7]);
   reservoir_temperature = atof(arg[8]);
   chemical_potential = atof(arg[9]);
   displace = atof(arg[10]);
 
   if (nexchanges < 0) error->all(FLERR,"Illegal fix gcmc command");
   if (nmcmoves < 0) error->all(FLERR,"Illegal fix gcmc command");
   if (seed <= 0) error->all(FLERR,"Illegal fix gcmc command");
   if (reservoir_temperature < 0.0)
     error->all(FLERR,"Illegal fix gcmc command");
   if (displace < 0.0) error->all(FLERR,"Illegal fix gcmc command");
 
   // set defaults
 
   molflag = 0;
   max_rotation_angle = 10*MY_PI/180;
   regionflag = 0; 
   iregion = -1; 
   region_volume = 0;
   max_region_attempts = 1000; 
   rotation_group = 0;
   rotation_groupbit = 0;
   rotation_inversegroupbit = 0;
 
   // read options from end of input line
 
   options(narg-11,&arg[11]);
 
   // random number generator, same for all procs
 
   random_equal = new RanPark(lmp,seed);
 
   // random number generator, not the same for all procs
 
   random_unequal = new RanPark(lmp,seed);
   
   // error checks on region and its extent being inside simulation box
 
   region_xlo = region_xhi = region_ylo = region_yhi = 
     region_zlo = region_zhi = 0.0;
   if (regionflag) {
     if (domain->regions[iregion]->bboxflag == 0)
       error->all(FLERR,"Fix gcmc region does not support a bounding box");
     if (domain->regions[iregion]->dynamic_check())
       error->all(FLERR,"Fix gcmc region cannot be dynamic");
     
     region_xlo = domain->regions[iregion]->extent_xlo;
     region_xhi = domain->regions[iregion]->extent_xhi;
     region_ylo = domain->regions[iregion]->extent_ylo;
     region_yhi = domain->regions[iregion]->extent_yhi;
     region_zlo = domain->regions[iregion]->extent_zlo;
     region_zhi = domain->regions[iregion]->extent_zhi;
 
     if (region_xlo < domain->boxlo[0] || region_xhi > domain->boxhi[0] ||
         region_ylo < domain->boxlo[1] || region_yhi > domain->boxhi[1] ||
         region_zlo < domain->boxlo[2] || region_zhi > domain->boxhi[2])
       error->all(FLERR,"Fix gcmc region extends outside simulation box");
 
     // estimate region volume using MC trials
       
     double coord[3];
     int inside = 0;
     int attempts = 10000000;
     for (int i = 0; i < attempts; i++) {
       coord[0] = region_xlo + random_equal->uniform() * (region_xhi-region_xlo);
       coord[1] = region_ylo + random_equal->uniform() * (region_yhi-region_ylo);
       coord[2] = region_zlo + random_equal->uniform() * (region_zhi-region_zlo);
       if (domain->regions[iregion]->match(coord[0],coord[1],coord[2]) != 0) inside++;
     }
 
     double max_region_volume = (region_xhi - region_xlo)*
      (region_yhi - region_ylo)*(region_zhi - region_zlo);
 
     region_volume = max_region_volume*static_cast<double> (inside)/
      static_cast<double> (attempts);
   }
 
   // compute the number of MC cycles that occur nevery timesteps
 
   ncycles = nexchanges + nmcmoves;
 
   // set up reneighboring
 
   force_reneighbor = 1;
   next_reneighbor = update->ntimestep + 1;
 
   // zero out counters
 
   ntranslation_attempts = 0.0;
   ntranslation_successes = 0.0;
   nrotation_attempts = 0.0;
   nrotation_successes = 0.0;
   ndeletion_attempts = 0.0;
   ndeletion_successes = 0.0;
   ninsertion_attempts = 0.0;
   ninsertion_successes = 0.0;
 
   gcmc_nmax = 0;
   local_gas_list = NULL;
 
   model_atom = NULL;
 }
 
 /* ----------------------------------------------------------------------
    parse optional parameters at end of input line
 ------------------------------------------------------------------------- */
 
 void FixGCMC::options(int narg, char **arg)
 {
   if (narg < 0) error->all(FLERR,"Illegal fix gcmc command");
 
   int iarg = 0;
   while (iarg < narg) {
   if (strcmp(arg[iarg],"molecule") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal fix gcmc command");
       if (strcmp(arg[iarg+1],"no") == 0) molflag = 0;
       else if (strcmp(arg[iarg+1],"yes") == 0) molflag = 1;
       else error->all(FLERR,"Illegal fix gcmc command");
       iarg += 2;
     } else if (strcmp(arg[iarg],"region") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal fix gcmc command");
       iregion = domain->find_region(arg[iarg+1]);
       if (iregion == -1)
         error->all(FLERR,"Region ID for fix gcmc does not exist");
       int n = strlen(arg[iarg+1]) + 1;
       idregion = new char[n];
       strcpy(idregion,arg[iarg+1]);
       regionflag = 1;
       iarg += 2;
     } else if (strcmp(arg[iarg],"maxangle") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal fix gcmc command");
       max_rotation_angle = atof(arg[iarg+1]);
       max_rotation_angle *= MY_PI/180;
       iarg += 2;
     } else error->all(FLERR,"Illegal fix gcmc command");
   }
 }
 
 /* ---------------------------------------------------------------------- */
 
 FixGCMC::~FixGCMC()
 {
   delete random_equal;
   delete random_unequal;
   memory->destroy(local_gas_list);
   memory->destroy(atom_coord);
   memory->destroy(model_atom_buf);
   delete model_atom;
 }
 
 /* ---------------------------------------------------------------------- */
 
 int FixGCMC::setmask()
 {
   int mask = 0;
   mask |= PRE_EXCHANGE;
   return mask;
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixGCMC::init()
 {
   int *type = atom->type;
 
   if (molflag == 0) {
     if (ngcmc_type <= 0 || ngcmc_type > atom->ntypes)
       error->all(FLERR,"Invalid atom type in fix gcmc command");
   }
 
   // if molflag not set, warn if any deletable atom has a mol ID
 
   if (molflag == 0 && atom->molecule_flag) {
     int *molecule = atom->molecule;
     int *mask = atom->mask;
     int flag = 0;
     for (int i = 0; i < atom->nlocal; i++)
       if (type[i] == ngcmc_type)
         if (molecule[i]) flag = 1;
     int flagall;
     MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_SUM,world);
     if (flagall && comm->me == 0)
       error->all(FLERR,
        "Fix gcmc cannot exchange individual atoms belonging to a molecule");
   }
 
   // if molflag set, check for unset mol IDs
 
   if (molflag == 1) {
     int *molecule = atom->molecule;
     int *mask = atom->mask;
     int flag = 0;
     for (int i = 0; i < atom->nlocal; i++)
       if (mask[i] == groupbit)
         if (molecule[i] == 0) flag = 1;
     int flagall;
     MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_SUM,world);
     if (flagall && comm->me == 0)
       error->all(FLERR,
        "All mol IDs should be set for fix gcmc group atoms");
   }
 
   if ((molflag && (atom->molecule_flag == 0)) || 
       (molflag && ((!atom->tag_enable) || (!atom->map_style))))
     error->all(FLERR,
      "Fix gcmc molecule command requires that atoms have molecule attributes");
 
   if (force->pair->single_enable == 0)
     error->all(FLERR,"Fix gcmc incompatible with given pair_style");
 
   if (domain->dimension == 2)
     error->all(FLERR,"Cannot use fix gcmc in a 2d simulation");
 
   if (domain->triclinic == 1)
     error->all(FLERR,"Cannot use fix gcmc with a triclinic box");
 
   // create a new group for rotation molecules
 
   if (molflag) {
     char **group_arg = new char*[3];
     group_arg[0] = (char *) "rotation_gas_atoms";
     group_arg[1] = (char *) "molecule";
     char digits[12];
     sprintf(digits,"%d",ngcmc_type);
     group_arg[2] = digits;
     group->assign(3,group_arg);
     rotation_group = group->find(group_arg[0]);
     if (rotation_group == -1) 
       error->all(FLERR,"Could not find fix gcmc rotation group ID");
     rotation_groupbit = group->bitmask[rotation_group];
     rotation_inversegroupbit = rotation_groupbit ^ ~0;
     delete [] group_arg;
   }
     
   // get all of the needed molecule data if molflag, 
   // otherwise just get the gas mass
   
   if (molflag) get_model_molecule();
   else gas_mass = atom->mass[ngcmc_type];
   
   if (gas_mass <= 0.0)
     error->all(FLERR,"Illegal fix gcmc gas mass <= 0");
   
   // check that no deletable atoms are in atom->firstgroup
   // deleting such an atom would not leave firstgroup atoms first
   
   if (atom->firstgroup >= 0) {
     int *mask = atom->mask;
     int firstgroupbit = group->bitmask[atom->firstgroup];
 
     int flag = 0;
     for (int i = 0; i < atom->nlocal; i++)
       if ((mask[i] == groupbit) && (mask[i] && firstgroupbit)) flag = 1;
     
     int flagall;
     MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_SUM,world);
 
     if (flagall)
       error->all(FLERR,"Cannot do GCMC on atoms in atom_modify first group");
   }
   
   // compute beta, lambda, sigma, and the zz factor
 
   beta = 1.0/(force->boltz*reservoir_temperature);
   double lambda = sqrt(force->hplanck*force->hplanck/
                        (2.0*MY_PI*gas_mass*force->mvv2e*
                         force->boltz*reservoir_temperature));
   sigma = sqrt(force->boltz*reservoir_temperature/gas_mass/force->mvv2e);
   zz = exp(beta*chemical_potential)/(pow(lambda,3.0));
   
   imagetmp = ((tagint) IMGMAX << IMG2BITS) | 
              ((tagint) IMGMAX << IMGBITS) | IMGMAX;
 }
 
 /* ----------------------------------------------------------------------
    attempt Monte Carlo translations, rotations, insertions, and deletions
    done before exchange, borders, reneighbor
    so that ghost atoms and neighbor lists will be correct
 ------------------------------------------------------------------------- */
 
 void FixGCMC::pre_exchange()
 {
   // just return if should not be called on this timestep
 
   if (next_reneighbor != update->ntimestep) return;
 
   xlo = domain->boxlo[0];
   xhi = domain->boxhi[0];
   ylo = domain->boxlo[1];
   yhi = domain->boxhi[1];
   zlo = domain->boxlo[2];
   zhi = domain->boxhi[2];
   sublo = domain->sublo;
   subhi = domain->subhi;
 
   if (regionflag) volume = region_volume;
   else volume = domain->xprd * domain->yprd * domain->zprd;
 
   update_gas_atoms_list();
 
   if (molflag) {
     for (int i = 0; i < ncycles; i++) {
       int random_int_fraction =
         static_cast<int>(random_equal->uniform()*ncycles) + 1;
       if (random_int_fraction <= nmcmoves) {
         if (random_equal->uniform() < 0.5) attempt_molecule_translation();
         else attempt_molecule_rotation();
       } else {
         if (random_equal->uniform() < 0.5) attempt_molecule_deletion();
         else attempt_molecule_insertion();
       }
     }
   } else {
     for (int i = 0; i < ncycles; i++) {
       int random_int_fraction =
         static_cast<int>(random_equal->uniform()*ncycles) + 1;
       if (random_int_fraction <= nmcmoves) {
         attempt_atomic_translation();
       } else {
         if (random_equal->uniform() < 0.5) attempt_atomic_deletion();
         else attempt_atomic_insertion();
       }
     }
   }
 
   next_reneighbor = update->ntimestep + nevery;
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_atomic_translation()
 {
   ntranslation_attempts += 1.0;
   
   if (ngas == 0) return;
 
   int i;
   if (regionflag) i = pick_random_gas_atom_in_region();
   else i = pick_random_gas_atom();
   
   int success = 0;
   if (i >= 0) {
     double **x = atom->x;
     double energy_before = energy(i,ngcmc_type,-1,x[i]);
     double rsq = 1.1;
     double rx,ry,rz;
     rx = ry = rz = 0.0;
     while (rsq > 1.0) {
       rx = 2*random_unequal->uniform() - 1.0;
       ry = 2*random_unequal->uniform() - 1.0;
       rz = 2*random_unequal->uniform() - 1.0;
       rsq = rx*rx + ry*ry + rz*rz;
     }
     double coord[3];
     coord[0] = x[i][0] + displace*rx;
     coord[1] = x[i][1] + displace*ry;
     coord[2] = x[i][2] + displace*rz;
     double energy_after = energy(i,ngcmc_type,-1,coord);
     if (random_unequal->uniform() < exp(-beta*(energy_after - energy_before))) {
       x[i][0] = coord[0];
       x[i][1] = coord[1];
       x[i][2] = coord[2];
       success = 1;
     }
   }
 
   int success_all = 0;
   MPI_Allreduce(&success,&success_all,1,MPI_INT,MPI_MAX,world);
 
   if (success_all) {
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ntranslation_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_atomic_deletion()
 {
   ndeletion_attempts += 1.0;
 
   if (ngas == 0) return;
   
   int i;
   if (regionflag) i = pick_random_gas_atom_in_region();
   else i = pick_random_gas_atom();
 
   int success = 0;
   if (i >= 0) {
     double deletion_energy = energy(i,ngcmc_type,-1,atom->x[i]);
     if (random_unequal->uniform() < ngas*exp(beta*deletion_energy)/(zz*volume)) {
       atom->avec->copy(atom->nlocal-1,i,1);
       atom->nlocal--;
       success = 1;
     }
   }
 
   int success_all = 0;
   MPI_Allreduce(&success,&success_all,1,MPI_INT,MPI_MAX,world);
 
   if (success_all) {
     if (atom->tag_enable) {
       atom->natoms--;
       if (atom->map_style) atom->map_init();
     }
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ndeletion_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_atomic_insertion()
 {
   ninsertion_attempts += 1.0;
 
   double coord[3];
   if (regionflag) {
     int region_attempt = 0;
     coord[0] = region_xlo + random_equal->uniform() * (region_xhi-region_xlo);
     coord[1] = region_ylo + random_equal->uniform() * (region_yhi-region_ylo);
     coord[2] = region_zlo + random_equal->uniform() * (region_zhi-region_zlo);
     while (domain->regions[iregion]->match(coord[0],coord[1],coord[2]) == 0) {
       coord[0] = region_xlo + random_equal->uniform() * (region_xhi-region_xlo);
       coord[1] = region_ylo + random_equal->uniform() * (region_yhi-region_ylo);
       coord[2] = region_zlo + random_equal->uniform() * (region_zhi-region_zlo);
       region_attempt++;
       if (region_attempt >= max_region_attempts) return;
     }
   } else {
     coord[0] = xlo + random_equal->uniform() * (xhi-xlo);
     coord[1] = ylo + random_equal->uniform() * (yhi-ylo);
     coord[2] = zlo + random_equal->uniform() * (zhi-zlo);
   }
 
   int proc_flag = 0;
   if (coord[0] >= sublo[0] && coord[0] < subhi[0] &&
       coord[1] >= sublo[1] && coord[1] < subhi[1] &&
       coord[2] >= sublo[2] && coord[2] < subhi[2]) proc_flag = 1;
 
   int success = 0;
   if (proc_flag) {
     double insertion_energy = energy(-1,ngcmc_type,-1,coord);
     if (random_unequal->uniform() <
         zz*volume*exp(-beta*insertion_energy)/(ngas+1)) {
       atom->avec->create_atom(ngcmc_type,coord);
       int m = atom->nlocal - 1;
       atom->mask[m] = 1 | groupbit;
       atom->v[m][0] = random_unequal->gaussian()*sigma;
       atom->v[m][1] = random_unequal->gaussian()*sigma;
       atom->v[m][2] = random_unequal->gaussian()*sigma;
 
       int nfix = modify->nfix;
       Fix **fix = modify->fix;
       for (int j = 0; j < nfix; j++)
         if (fix[j]->create_attribute) fix[j]->set_arrays(m);
 
       success = 1;
     }
   }
 
   int success_all = 0;
   MPI_Allreduce(&success,&success_all,1,MPI_INT,MPI_MAX,world);
 
   if (success_all) {
     if (atom->tag_enable) {
       atom->natoms++;
       atom->tag_extend();
       if (atom->map_style) atom->map_init();
     }
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ninsertion_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_molecule_translation()
 {
   ntranslation_attempts += 1.0;
 
   if (ngas == 0) return;
 
   int translation_molecule;
   if (regionflag) translation_molecule = pick_random_gas_molecule_in_region();
   else translation_molecule = pick_random_gas_molecule();
   if (translation_molecule == -1) return;
 
   double energy_before_sum = molecule_energy(translation_molecule);
   
   double **x = atom->x;
   double rx,ry,rz;
   double com_displace[3],coord[3];
   double rsq = 1.1;
   while (rsq > 1.0) {
     rx = 2*random_equal->uniform() - 1.0;
     ry = 2*random_equal->uniform() - 1.0;
     rz = 2*random_equal->uniform() - 1.0;
     rsq = rx*rx + ry*ry + rz*rz;
   }
   com_displace[0] = displace*rx;
   com_displace[1] = displace*ry;
   com_displace[2] = displace*rz;
 
   double energy_after = 0.0;
   for (int i = 0; i < atom->nlocal; i++) {
     if (atom->molecule[i] == translation_molecule) {
       coord[0] = x[i][0] + com_displace[0];
       coord[1] = x[i][1] + com_displace[1];
       coord[2] = x[i][2] + com_displace[2];
       energy_after += energy(i,atom->type[i],translation_molecule,coord);
     }
   }
 
   double energy_after_sum = 0.0;
   MPI_Allreduce(&energy_after,&energy_after_sum,1,MPI_DOUBLE,MPI_SUM,world);
 
   if (random_equal->uniform() < exp(-beta*(energy_after_sum - energy_before_sum))) {
     for (int i = 0; i < atom->nlocal; i++) {
       if (atom->molecule[i] == translation_molecule) {
         x[i][0] += com_displace[0];
         x[i][1] += com_displace[1];
         x[i][2] += com_displace[2];
       }
     }
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ntranslation_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_molecule_rotation()
 {
   nrotation_attempts += 1.0;
 
   if (ngas == 0) return;
 
   int rotation_molecule;
   if (regionflag) rotation_molecule = pick_random_gas_molecule_in_region();
   else rotation_molecule = pick_random_gas_molecule();
   if (rotation_molecule == -1) return;
   
   double energy_before_sum = molecule_energy(rotation_molecule);
 
   int nlocal = atom->nlocal;
   int *mask = atom->mask;
   for (int i = 0; i < nlocal; i++) {
     if (atom->molecule[i] == rotation_molecule) {
       mask[i] |= rotation_groupbit;
     } else {
       mask[i] &= rotation_inversegroupbit;
     }
   }
 
   double com[3];
   com[0] = com[1] = com[2] = 0.0;
   group->xcm(rotation_group,gas_mass,com);
 
   double rot[9];
   get_rotation_matrix(max_rotation_angle,&rot[0]);
 
   double **x = atom->x;
   tagint *image = atom->image;
   double energy_after = 0.0;
   int n = 0;
   for (int i = 0; i < nlocal; i++) {
     if (mask[i] & rotation_groupbit) {
       double xtmp[3];
       domain->unmap(x[i],image[i],xtmp);
       xtmp[0] -= com[0];
       xtmp[1] -= com[1];
       xtmp[2] -= com[2];
       atom_coord[n][0] = rot[0]*xtmp[0] + rot[1]*xtmp[1] + rot[2]*xtmp[2] + com[0];
       atom_coord[n][1] = rot[3]*xtmp[0] + rot[4]*xtmp[1] + rot[5]*xtmp[2] + com[1];
       atom_coord[n][2] = rot[6]*xtmp[0] + rot[7]*xtmp[1] + rot[8]*xtmp[2] + com[2];
       xtmp[0] = atom_coord[n][0];
       xtmp[1] = atom_coord[n][1];
       xtmp[2] = atom_coord[n][2];
       domain->remap(xtmp);
       energy_after += energy(i,atom->type[i],rotation_molecule,xtmp);
       n++;
     }
   }
 
   double energy_after_sum = 0.0;
   MPI_Allreduce(&energy_after,&energy_after_sum,1,MPI_DOUBLE,MPI_SUM,world);
 
   if (random_equal->uniform() < exp(-beta*(energy_after_sum - energy_before_sum))) {
     int n = 0;
     for (int i = 0; i < nlocal; i++) {
       if (mask[i] & rotation_groupbit) {
         image[i] = imagetmp;
         x[i][0] = atom_coord[n][0];
         x[i][1] = atom_coord[n][1];
         x[i][2] = atom_coord[n][2];
         domain->remap(x[i],image[i]);
         n++;
       }
     }
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     nrotation_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_molecule_deletion()
 {
   ndeletion_attempts += 1.0;
 
   if (ngas == 0) return;
   
   int deletion_molecule;
   if (regionflag) deletion_molecule = pick_random_gas_molecule_in_region();
   else deletion_molecule = pick_random_gas_molecule();
   if (deletion_molecule == -1) return;
 
   double deletion_energy_sum = molecule_energy(deletion_molecule);
 
   if (random_equal->uniform() < ngas*exp(beta*deletion_energy_sum)/(zz*volume)) {
     int i = 0;
     while (i < atom->nlocal) {
       if (atom->molecule[i] == deletion_molecule) {
         atom->avec->copy(atom->nlocal-1,i,1);
         atom->nlocal--;
       } else i++;
     }
     atom->natoms -= natoms_per_molecule;
     atom->map_init();
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ndeletion_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 void FixGCMC::attempt_molecule_insertion()
 {
   ninsertion_attempts += 1.0;
 
   double xprd = domain->xprd;
   double yprd = domain->yprd;
   double zprd = domain->zprd;
 
   double com_coord[3];
   if (regionflag) {
     int region_attempt = 0;
     com_coord[0] = region_xlo + random_equal->uniform() * (region_xhi-region_xlo);
     com_coord[1] = region_ylo + random_equal->uniform() * (region_yhi-region_ylo);
     com_coord[2] = region_zlo + random_equal->uniform() * (region_zhi-region_zlo);
     while (domain->regions[iregion]->match(com_coord[0],com_coord[1],com_coord[2]) == 0) {
       com_coord[0] = region_xlo + random_equal->uniform() * (region_xhi-region_xlo);
       com_coord[1] = region_ylo + random_equal->uniform() * (region_yhi-region_ylo);
       com_coord[2] = region_zlo + random_equal->uniform() * (region_zhi-region_zlo);
       region_attempt++;
       if (region_attempt >= max_region_attempts) return;
     }
   } else {
     com_coord[0] = xlo + random_equal->uniform() * (xhi-xlo);
     com_coord[1] = ylo + random_equal->uniform() * (yhi-ylo);
     com_coord[2] = zlo + random_equal->uniform() * (zhi-zlo);
   }
 
   double rot[9];
   get_rotation_matrix(MY_2PI,&rot[0]);
 
   double **model_x = model_atom->x;
   double insertion_energy = 0.0;
   bool procflag[natoms_per_molecule];
   for (int i = 0; i < natoms_per_molecule; i++) {
     atom_coord[i][0] = rot[0]*model_x[i][0] + rot[1]*model_x[i][1] + rot[2]*model_x[i][2] + com_coord[0];
     atom_coord[i][1] = rot[3]*model_x[i][0] + rot[4]*model_x[i][1] + rot[5]*model_x[i][2] + com_coord[1];
     atom_coord[i][2] = rot[6]*model_x[i][0] + rot[7]*model_x[i][1] + rot[8]*model_x[i][2] + com_coord[2];
 
     double xtmp[3];
     xtmp[0] = atom_coord[i][0];
     xtmp[1] = atom_coord[i][1];
     xtmp[2] = atom_coord[i][2];
     domain->remap(xtmp);
 
     procflag[i] = false;
     if (xtmp[0] >= sublo[0] && xtmp[0] < subhi[0] &&
         xtmp[1] >= sublo[1] && xtmp[1] < subhi[1] &&
         xtmp[2] >= sublo[2] && xtmp[2] < subhi[2]) {
       procflag[i] = true;
       insertion_energy += energy(-1,model_atom->type[i],-1,xtmp);
     }
   }
 
   double insertion_energy_sum = 0.0;
   MPI_Allreduce(&insertion_energy,&insertion_energy_sum,1,MPI_DOUBLE,MPI_SUM,world);
 
   if (random_equal->uniform() < zz*volume*exp(-beta*insertion_energy_sum)/(ngas+1)) {  
     maxmol++;
     if (maxmol >= MAXSMALLINT) 
       error->all(FLERR,"Fix gcmc ran out of available molecule IDs");
 
     int maxtag = 0;
     for (int i = 0; i < atom->nlocal; i++) maxtag = MAX(maxtag,atom->tag[i]);
     int maxtag_all;
     MPI_Allreduce(&maxtag,&maxtag_all,1,MPI_INT,MPI_MAX,world);
     int atom_offset = maxtag_all;
 
     int k = 0;
     double **x = atom->x;
     double **v = atom->v;
     tagint *image = atom->image;
     int *molecule = atom->molecule;
     int *tag = atom->tag;
     for (int i = 0; i < natoms_per_molecule; i++) {
       k += atom->avec->unpack_restart(&model_atom_buf[k]);
       if (procflag[i]) {
         int m = atom->nlocal - 1;
         image[m] = imagetmp;
         x[m][0] = atom_coord[i][0];
         x[m][1] = atom_coord[i][1];
         x[m][2] = atom_coord[i][2];
         domain->remap(x[m],image[m]);
         atom->molecule[m] = maxmol;
         tag[m] += atom_offset;
         v[m][0] = random_unequal->gaussian()*sigma;
         v[m][1] = random_unequal->gaussian()*sigma;
         v[m][2] = random_unequal->gaussian()*sigma;
         
         if (atom->avec->bonds_allow)
           for (int j = 0; j < atom->num_bond[m]; j++)
             atom->bond_atom[m][j] += atom_offset;
         if (atom->avec->angles_allow)
           for (int j = 0; j < atom->num_angle[m]; j++) {
             atom->angle_atom1[m][j] += atom_offset;
             atom->angle_atom2[m][j] += atom_offset;
             atom->angle_atom3[m][j] += atom_offset;
           }
         if (atom->avec->dihedrals_allow)
           for (int j = 0; j < atom->num_dihedral[m]; j++) {
             atom->dihedral_atom1[m][j] += atom_offset;
             atom->dihedral_atom2[m][j] += atom_offset;
             atom->dihedral_atom3[m][j] += atom_offset;
             atom->dihedral_atom4[m][j] += atom_offset;
           }
         if (atom->avec->impropers_allow)
           for (int j = 0; j < atom->num_improper[m]; j++) {
             atom->improper_atom1[m][j] += atom_offset;
             atom->improper_atom2[m][j] += atom_offset;
             atom->improper_atom3[m][j] += atom_offset;
             atom->improper_atom4[m][j] += atom_offset;
           }
         
         int nfix = modify->nfix;
         Fix **fix = modify->fix;
         for (int j = 0; j < nfix; j++)
           if (fix[j]->create_attribute) fix[j]->set_arrays(m);
 
       } else atom->nlocal--;
     }
     atom->natoms += natoms_per_molecule;
     atom->map_init();
+    atom->nghost = 0;
     comm->borders();
     update_gas_atoms_list();
     ninsertion_successes += 1.0;
   }
 }
 
 /* ----------------------------------------------------------------------
    compute particle's interaction energy with the rest of the system
 ------------------------------------------------------------------------- */
 
 double FixGCMC::energy(int i, int itype, int imolecule, double *coord)
 {
   double delx,dely,delz,rsq;
 
   double **x = atom->x;
   int *type = atom->type;
   int *molecule = atom->molecule;
   int nall = atom->nlocal + atom->nghost;
   pair = force->pair;
   cutsq = force->pair->cutsq;
 
   double fpair = 0.0;
   double factor_coul = 1.0;
   double factor_lj = 1.0;
 
   double total_energy = 0.0;
   for (int j = 0; j < nall; j++) {
 
     if (i == j) continue;
     if (molflag)
       if (imolecule == molecule[j]) continue;
 
     delx = coord[0] - x[j][0];
     dely = coord[1] - x[j][1];
     delz = coord[2] - x[j][2];
     rsq = delx*delx + dely*dely + delz*delz;
     int jtype = type[j];
 
     if (rsq < cutsq[itype][jtype])
       total_energy +=
         pair->single(i,j,itype,jtype,rsq,factor_coul,factor_lj,fpair);
   }
 
   return total_energy;
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 int FixGCMC::pick_random_gas_atom()
 {
   int i = -1;
   int iwhichglobal = static_cast<int> (ngas*random_equal->uniform());
   if ((iwhichglobal >= ngas_before) &&
       (iwhichglobal < ngas_before + ngas_local)) {
     int iwhichlocal = iwhichglobal - ngas_before;
     i = local_gas_list[iwhichlocal];
   }
 
   return i;
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 int FixGCMC::pick_random_gas_atom_in_region()
 {
   int i = -1;
   int i_own_candidate = 0;
   int i_own_candidate_all = 0;
   int region_attempt = 0;
   double **x = atom->x;
   while (!i_own_candidate_all) {
     int iwhichglobal = static_cast<int> (ngas*random_equal->uniform());
     if ((iwhichglobal >= ngas_before) &&
         (iwhichglobal < ngas_before + ngas_local)) {
       i_own_candidate = 1;
       int iwhichlocal = iwhichglobal - ngas_before;
       i = local_gas_list[iwhichlocal];
       if (domain->regions[iregion]->match(x[i][0],x[i][1],x[i][2]) == 0)
         i_own_candidate = 0;
     }
     MPI_Allreduce(&i_own_candidate,&i_own_candidate_all,1,MPI_INT,MPI_MAX,world);
     region_attempt++;
     if (region_attempt >= max_region_attempts) return -1;
   }
 
   return i;
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 int FixGCMC::pick_random_gas_molecule()
 {
   int iwhichglobal = static_cast<int> (ngas*random_equal->uniform());
   int gas_molecule_id = 0;
   if ((iwhichglobal >= ngas_before) &&
       (iwhichglobal < ngas_before + ngas_local)) {
     int iwhichlocal = iwhichglobal - ngas_before;
     int i = local_gas_list[iwhichlocal];
     gas_molecule_id = atom->molecule[i];
   }
 
   int gas_molecule_id_all = 0;
   MPI_Allreduce(&gas_molecule_id,&gas_molecule_id_all,1,MPI_INT,MPI_MAX,world);
   
   return gas_molecule_id_all;
 }
 
 /* ----------------------------------------------------------------------
 ------------------------------------------------------------------------- */
 
 int FixGCMC::pick_random_gas_molecule_in_region()
 {
   int region_attempt = 0;
   int gas_molecule_id = 0;
   int gas_molecule_id_all = 0;
   double **x = atom->x;
   while (!gas_molecule_id_all) {
     int iwhichglobal = static_cast<int> (ngas*random_equal->uniform());
     if ((iwhichglobal >= ngas_before) &&
         (iwhichglobal < ngas_before + ngas_local)) {
       int iwhichlocal = iwhichglobal - ngas_before;
       int i = local_gas_list[iwhichlocal];
       if (domain->regions[iregion]->match(x[i][0],x[i][1],x[i][2]) != 0) {
         gas_molecule_id = atom->molecule[i];
       }
     }
     gas_molecule_id_all = 0;
     MPI_Allreduce(&gas_molecule_id,&gas_molecule_id_all,1,MPI_INT,MPI_MAX,world);
     region_attempt++;
     if (region_attempt >= max_region_attempts) return -1;
   }
 
   return gas_molecule_id_all;
 }
 
 /* ----------------------------------------------------------------------
    compute the energy of the given gas molecule in its current position 
    sum across all procs that own atoms of the given molecule
 ------------------------------------------------------------------------- */
 
 double FixGCMC::molecule_energy(int gas_molecule_id)
 {
   double mol_energy = 0.0;
   for (int i = 0; i < atom->nlocal; i++)
     if (atom->molecule[i] == gas_molecule_id) {
       mol_energy += energy(i,atom->type[i],gas_molecule_id,atom->x[i]);
     }
 
   double mol_energy_sum = 0.0;
   MPI_Allreduce(&mol_energy,&mol_energy_sum,1,MPI_DOUBLE,MPI_SUM,world);
   
   return mol_energy_sum;
 }
 
 /* ----------------------------------------------------------------------
    compute a 3x3 rotation matrix using 3 random Euler angles, 
    each with a random maximum value supplied by the caller
 ------------------------------------------------------------------------- */
 
 void FixGCMC::get_rotation_matrix(double max_angle, double *rot)
 {
   double angle_x = max_angle*random_equal->uniform();
   double angle_y = max_angle*random_equal->uniform();
   double angle_z = max_angle*random_equal->uniform();
   
   double a = cos(angle_x);
   double b = sin(angle_x);
   double c = cos(angle_y);
   double d = sin(angle_y);
   double e = cos(angle_z);
   double f = sin(angle_z);
   double ad = a*d;
   double bd = b*d;
 
   rot[0] = c*e;
   rot[1] = -c*f;
   rot[2] = -d;
   rot[3] = -bd*e + a*f;
   rot[4] = bd*f + a*e;
   rot[5] = -b*c;
   rot[6] = ad*e + b*f;
   rot[7] = -ad*f + b*e;
   rot[8] = a*c;
 }
 
 /* ----------------------------------------------------------------------
    when using the molecule capability, populate model atom arrays from
    the model molecule provided by the user that will then be used to build 
    inserted molecules
 ------------------------------------------------------------------------- */
 
 void FixGCMC::get_model_molecule()
 {
   // find out how many atoms are in the model molecule
   // just loop through all of the atoms I own, then sum up across procs
   
   int model_molecule_number = ngcmc_type;
   int natoms_per_molecule_local = 0;
   for (int i = 0; i < atom->nlocal; i++) {
     if (atom->molecule[i] == model_molecule_number) {
       natoms_per_molecule_local++;
     }
   }
 
   natoms_per_molecule = 0;
   MPI_Allreduce(&natoms_per_molecule_local,&natoms_per_molecule,1,MPI_INT,MPI_MAX,world);
 
   if (natoms_per_molecule == 0)
     error->all(FLERR,"Fix gcmc could not find any atoms in the user-supplied template molecule");
   
   memory->create(atom_coord,natoms_per_molecule,3,"fixGCMC:atom_coord");
 
   // maxmol = largest molecule tag across all existing atoms
 
   maxmol = 0;
   if (atom->molecular) {
     for (int i = 0; i < atom->nlocal; i++) maxmol = MAX(atom->molecule[i],maxmol);
     int maxmol_all;
     MPI_Allreduce(&maxmol,&maxmol_all,1,MPI_INT,MPI_MAX,world);
     maxmol = maxmol_all;
   }
 
   // communication buffer for model atom's info
   // max_size = largest buffer needed by any proc
   // must do before new Atom class created,
   //   since size_restart() uses atom->nlocal
 
   int max_size;
   int buf_send_size = atom->avec->size_restart(); 
   
   MPI_Allreduce(&buf_send_size,&max_size,1,MPI_INT,MPI_MAX,world);
   double *buf;
   memory->create(buf,max_size,"fixGCMC:buf");
   
   // create storage space for the model molecule's atoms
   // create a new atom object called atom to store the data
   
   // old_atom = original atom class
   // atom = new model atom class
   // if old_atom style was hybrid, pass sub-style names to create_avec
 
   Atom *old_atom = atom;
   atom = new Atom(lmp);
   atom->settings(old_atom);
   
   int nstyles = 0;
   char **keywords = NULL;
   if (strcmp(old_atom->atom_style,"hybrid") == 0) {
     AtomVecHybrid *avec_hybrid = (AtomVecHybrid *) old_atom->avec;
     nstyles = avec_hybrid->nstyles;
     keywords = avec_hybrid->keywords;
   }
   
   atom->create_avec(old_atom->atom_style,nstyles,keywords);
   
   // assign atom and topology counts in model atom class from old_atom
 
   atom->ntypes = old_atom->ntypes;
   atom->nbondtypes = old_atom->nbondtypes;
   atom->nangletypes = old_atom->nangletypes;
   atom->ndihedraltypes = old_atom->ndihedraltypes;
   atom->nimpropertypes = old_atom->nimpropertypes;
   atom->bond_per_atom = old_atom->bond_per_atom;
   atom->angle_per_atom = old_atom->angle_per_atom;
   atom->dihedral_per_atom = old_atom->dihedral_per_atom;
   atom->improper_per_atom = old_atom->improper_per_atom;
   atom->extra_bond_per_atom = old_atom->extra_bond_per_atom;
   atom->allocate_type_arrays();
   atom->avec->grow(natoms_per_molecule);
   
   // copy type arrays to model atom class
   
   if (atom->mass) {
     for (int itype = 1; itype <= atom->ntypes; itype++) {
       atom->mass_setflag[itype] = old_atom->mass_setflag[itype];
       if (atom->mass_setflag[itype]) atom->mass[itype] = old_atom->mass[itype];
     }
   }
   // loop over all procs
   // if this iteration of loop is me:
   //   pack my atom data into buf
   //   bcast it to all other procs
 
   AtomVec *old_avec = old_atom->avec;
   AtomVec *model_avec = atom->avec;
 
   int model_buf_size = 0;
   for (int iproc = 0; iproc < comm->nprocs; iproc++) {
     int nbuf_iproc = 0;
     if (comm->me == iproc) {
       for (int i = 0; i < old_atom->nlocal; i++) {
         if (old_atom->molecule[i] == model_molecule_number) {
           nbuf_iproc += old_avec->pack_restart(i,&buf[nbuf_iproc]);
         }
       }
     }
     MPI_Bcast(&nbuf_iproc,1,MPI_INT,iproc,world);
     MPI_Bcast(buf,nbuf_iproc,MPI_DOUBLE,iproc,world);
 
     model_buf_size += nbuf_iproc;
      
     int m = 0;
     while (m < nbuf_iproc)
       m += model_avec->unpack_restart(&buf[m]);
   }
 
   // free communication buffer 
 
   memory->destroy(buf);
   
   // make sure that the number of model atoms is equal to the number of atoms per gas molecule
   
   int nlocal = atom->nlocal;
   if (nlocal != natoms_per_molecule)
     error->all(FLERR,"Fix gcmc incorrect number of atoms per molecule");
   
   // compute the model molecule's mass and center-of-mass
   // then recenter model molecule on the origin
 
   double com[3]; 
   gas_mass = group->mass(0);
   group->xcm(0,gas_mass,com);
 
   double **x = atom->x;  
   for (int i = 0; i < nlocal; i++) {
     domain->unmap(x[i],atom->image[i]);
     x[i][0] -= com[0];
     x[i][1] -= com[1];
     x[i][2] -= com[2];
   }
 
   int mintag = atom->tag[0];
   for (int i = 0; i < atom->nlocal; i++) mintag = MIN(mintag,atom->tag[i]);
   int atom_offset = mintag - 1;
   
   for (int i = 0; i < nlocal; i++) {
     atom->mask[i] = 1 | groupbit;
     atom->tag[i] -= atom_offset;
     if (atom->avec->bonds_allow)
       for (int j = 0; j < atom->num_bond[i]; j++)
         atom->bond_atom[i][j] -= atom_offset;
     if (atom->avec->angles_allow)
       for (int j = 0; j < atom->num_angle[i]; j++) {
         atom->angle_atom1[i][j] -= atom_offset;
         atom->angle_atom2[i][j] -= atom_offset;
         atom->angle_atom3[i][j] -= atom_offset;
       }
     if (atom->avec->dihedrals_allow)
       for (int j = 0; j < atom->num_dihedral[i]; j++) {
         atom->dihedral_atom1[i][j] -= atom_offset;
         atom->dihedral_atom2[i][j] -= atom_offset;
         atom->dihedral_atom3[i][j] -= atom_offset;
         atom->dihedral_atom4[i][j] -= atom_offset;
       }
     if (atom->avec->impropers_allow)
       for (int j = 0; j < atom->num_improper[i]; j++) {
         atom->improper_atom1[i][j] -= atom_offset;
         atom->improper_atom2[i][j] -= atom_offset;
         atom->improper_atom3[i][j] -= atom_offset;
         atom->improper_atom4[i][j] -= atom_offset;
       }
   }
 
   // pack model atoms into a buffer for use during molecule insertions
   
   memory->create(model_atom_buf,model_buf_size,"fixGCMC:model_atom_buf");
   int n = 0;
   for (int i = 0; i < nlocal; i++) 
     n += model_avec->pack_restart(i,&model_atom_buf[n]);
 
   // move atom to model_atom and restore old_atom class pointer back to atom
 
   model_atom = atom;
   atom = old_atom;
 }
 
 /* ----------------------------------------------------------------------
    update the list of gas atoms
 ------------------------------------------------------------------------- */
 
 void FixGCMC::update_gas_atoms_list()
 {
   if (atom->nlocal > gcmc_nmax) {
     memory->sfree(local_gas_list);
     gcmc_nmax = atom->nmax;
     local_gas_list = (int *) memory->smalloc(gcmc_nmax*sizeof(int),
      "GCMC:local_gas_list");
   }
 
   ngas_local = 0;
   for (int i = 0; i < atom->nlocal; i++) {
     if (atom->mask[i] & groupbit) {
       local_gas_list[ngas_local] = i;
       ngas_local++;
     }
   }
 
   MPI_Allreduce(&ngas_local,&ngas,1,MPI_INT,MPI_SUM,world);
   MPI_Scan(&ngas_local,&ngas_before,1,MPI_INT,MPI_SUM,world);
   ngas_before -= ngas_local;
 }
 
 /* ----------------------------------------------------------------------
   return acceptance ratios
 ------------------------------------------------------------------------- */
 
 double FixGCMC::compute_vector(int n)
 {
   if (n == 0) return ntranslation_attempts;
   if (n == 1) return ntranslation_successes;
   if (n == 2) return ninsertion_attempts;
   if (n == 3) return ninsertion_successes;
   if (n == 4) return ndeletion_attempts;
   if (n == 5) return ndeletion_successes;
   if (n == 6) return nrotation_attempts;
   if (n == 7) return nrotation_successes;
   return 0.0;
 }
 
 /* ----------------------------------------------------------------------
    memory usage of local atom-based arrays
 ------------------------------------------------------------------------- */
 
 double FixGCMC::memory_usage()
 {
   double bytes = gcmc_nmax * sizeof(int);
   return bytes;
 }
 
 /* ----------------------------------------------------------------------
    pack entire state of Fix into one write
 ------------------------------------------------------------------------- */
 
 void FixGCMC::write_restart(FILE *fp)
 {
   int n = 0;
   double list[4];
   list[n++] = random_equal->state();
   list[n++] = random_unequal->state();
   list[n++] = next_reneighbor;
 
   if (comm->me == 0) {
     int size = n * sizeof(double);
     fwrite(&size,sizeof(int),1,fp);
     fwrite(list,sizeof(double),n,fp);
   }
 }
 
 /* ----------------------------------------------------------------------
    use state info from restart file to restart the Fix
 ------------------------------------------------------------------------- */
 
 void FixGCMC::restart(char *buf)
 {
   int n = 0;
   double *list = (double *) buf;
 
   seed = static_cast<int> (list[n++]);
   random_equal->reset(seed);
 
   seed = static_cast<int> (list[n++]);
   random_unequal->reset(seed);
 
   next_reneighbor = static_cast<int> (list[n++]);
 }