diff --git a/src/ASPHERE/fix_npt_asphere.cpp b/src/ASPHERE/fix_npt_asphere.cpp
index 2625bc6391..205630376a 100755
--- a/src/ASPHERE/fix_npt_asphere.cpp
+++ b/src/ASPHERE/fix_npt_asphere.cpp
@@ -46,7 +46,7 @@ FixNPTAsphere::FixNPTAsphere(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTAsphere::FixNPTAsphere(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/ASPHERE/fix_nvt_asphere.cpp b/src/ASPHERE/fix_nvt_asphere.cpp
index 5b8b943ab4..f43e731c23 100755
--- a/src/ASPHERE/fix_nvt_asphere.cpp
+++ b/src/ASPHERE/fix_nvt_asphere.cpp
@@ -45,5 +45,5 @@ FixNVTAsphere::FixNVTAsphere(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/BODY/fix_nph_body.cpp b/src/BODY/fix_nph_body.cpp
index 1808b9ade8..99e33a3d22 100644
--- a/src/BODY/fix_nph_body.cpp
+++ b/src/BODY/fix_nph_body.cpp
@@ -50,7 +50,7 @@ FixNPHBody::FixNPHBody(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -68,5 +68,5 @@ FixNPHBody::FixNPHBody(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/BODY/fix_npt_body.cpp b/src/BODY/fix_npt_body.cpp
index 17014ba17c..077a7babd4 100755
--- a/src/BODY/fix_npt_body.cpp
+++ b/src/BODY/fix_npt_body.cpp
@@ -50,7 +50,7 @@ FixNPTBody::FixNPTBody(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -68,5 +68,5 @@ FixNPTBody::FixNPTBody(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/BODY/fix_nvt_body.cpp b/src/BODY/fix_nvt_body.cpp
index d6601f4966..464f42eae9 100755
--- a/src/BODY/fix_nvt_body.cpp
+++ b/src/BODY/fix_nvt_body.cpp
@@ -49,5 +49,5 @@ FixNVTBody::FixNVTBody(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/KOKKOS/fix_nph_kokkos.cpp b/src/KOKKOS/fix_nph_kokkos.cpp
index 350832a3d7..f3f7c271d6 100755
--- a/src/KOKKOS/fix_nph_kokkos.cpp
+++ b/src/KOKKOS/fix_nph_kokkos.cpp
@@ -47,7 +47,7 @@ FixNPHKokkos<DeviceType>::FixNPHKokkos(LAMMPS *lmp, int narg, char **arg) :
 
   this->modify->add_compute(3,newarg);
   delete [] newarg;
-  this->tflag = 1;
+  this->tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -65,7 +65,7 @@ FixNPHKokkos<DeviceType>::FixNPHKokkos(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = this->id_temp;
   this->modify->add_compute(4,newarg);
   delete [] newarg;
-  this->pflag = 1;
+  this->pcomputeflag = 1;
 }
 
 namespace LAMMPS_NS {
diff --git a/src/KOKKOS/fix_npt_kokkos.cpp b/src/KOKKOS/fix_npt_kokkos.cpp
index 3832fb3e57..bbc26b8e88 100755
--- a/src/KOKKOS/fix_npt_kokkos.cpp
+++ b/src/KOKKOS/fix_npt_kokkos.cpp
@@ -47,7 +47,7 @@ FixNPTKokkos<DeviceType>::FixNPTKokkos(LAMMPS *lmp, int narg, char **arg) :
 
   this->modify->add_compute(3,newarg);
   delete [] newarg;
-  this->tflag = 1;
+  this->tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -65,7 +65,7 @@ FixNPTKokkos<DeviceType>::FixNPTKokkos(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = this->id_temp;
   this->modify->add_compute(4,newarg);
   delete [] newarg;
-  this->pflag = 1;
+  this->pcomputeflag = 1;
 }
 
 namespace LAMMPS_NS {
diff --git a/src/KOKKOS/fix_nvt_kokkos.cpp b/src/KOKKOS/fix_nvt_kokkos.cpp
index bf6ce0de2b..c479251c33 100755
--- a/src/KOKKOS/fix_nvt_kokkos.cpp
+++ b/src/KOKKOS/fix_nvt_kokkos.cpp
@@ -46,7 +46,7 @@ FixNVTKokkos<DeviceType>::FixNVTKokkos(LAMMPS *lmp, int narg, char **arg) :
 
   this->modify->add_compute(3,newarg);
   delete [] newarg;
-  this->tflag = 1;
+  this->tcomputeflag = 1;
 }
 
 namespace LAMMPS_NS {
diff --git a/src/MANYBODY/pair_vashishta.cpp b/src/MANYBODY/pair_vashishta.cpp
index 7456c08791..aa030540f4 100755
--- a/src/MANYBODY/pair_vashishta.cpp
+++ b/src/MANYBODY/pair_vashishta.cpp
@@ -488,13 +488,16 @@ void PairVashishta::setup_params()
 
   // set cutsq using shortcut to reduce neighbor list for accelerated
   // calculations. cut must remain unchanged as it is a potential parameter
+  double tmp_par;
 
   for (m = 0; m < nparams; m++) {
     params[m].cutsq = params[m].cut * params[m].cut;
     params[m].cutsq2 = params[m].r0 * params[m].r0;
 
-    params[m].lam1inv = 1.0/params[m].lambda1;
-    params[m].lam4inv = 1.0/params[m].lambda4;
+    tmp_par = params[m].lambda1;
+    params[m].lam1inv = (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
+    tmp_par = params[m].lambda4;
+    params[m].lam4inv = (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
     params[m].zizj = params[m].zi*params[m].zj * force->qqr2e;
     // note that bigd does not have 1/2 factor
     params[m].mbigd = params[m].bigd;
@@ -502,8 +505,9 @@ void PairVashishta::setup_params()
     params[m].big2b = 2.0*params[m].bigb;
     params[m].big6w = 6.0*params[m].bigw;
 
-    params[m].rcinv = 1.0/params[m].cut;
-    params[m].rc2inv = 1.0/params[m].cutsq;
+    tmp_par = params[m].cut;
+    params[m].rcinv =  (tmp_par == 0.0) ? 0.0 : 1.0/tmp_par;
+    params[m].rc2inv = params[m].rcinv*params[m].rcinv;
     params[m].rc4inv = params[m].rc2inv*params[m].rc2inv;
     params[m].rc6inv = params[m].rc2inv*params[m].rc4inv;
     params[m].rceta = pow(params[m].rcinv,params[m].eta);
diff --git a/src/MC/fix_tfmc.cpp b/src/MC/fix_tfmc.cpp
index eea0a0bf31..8ce1308694 100755
--- a/src/MC/fix_tfmc.cpp
+++ b/src/MC/fix_tfmc.cpp
@@ -229,9 +229,12 @@ void FixTFMC::initial_integrate(int vflag)
   // zero com motion
   if (comflag == 1 && group->count(igroup) != 0) {
     MPI_Allreduce(xcm_d,xcm_dall,3,MPI_DOUBLE,MPI_SUM,world);
-    xcm_dall[0] /= masstotal;
-    xcm_dall[1] /= masstotal;
-    xcm_dall[2] /= masstotal;
+    if (masstotal > 0.0) {
+      xcm_dall[0] /= masstotal;
+      xcm_dall[1] /= masstotal;
+      xcm_dall[2] /= masstotal;
+    } else xcm_dall[0] = xcm_dall[1] = xcm_dall[2] = 0.0;
+    
     for (int i = 0; i < nlocal; i++) {
       if (mask[i] & groupbit) {
         if (xflag) x[i][0] -= xcm_dall[0];
diff --git a/src/RIGID/fix_rigid_nh.cpp b/src/RIGID/fix_rigid_nh.cpp
index 5db799e9f0..a2c6c338b7 100644
--- a/src/RIGID/fix_rigid_nh.cpp
+++ b/src/RIGID/fix_rigid_nh.cpp
@@ -148,6 +148,9 @@ FixRigidNH::FixRigidNH(LAMMPS *lmp, int narg, char **arg) :
 
   tcomputeflag = 0;
   pcomputeflag = 0;
+
+  id_temp = NULL;
+  id_press = NULL;
 }
 
 /* ---------------------------------------------------------------------- */
@@ -162,10 +165,8 @@ FixRigidNH::~FixRigidNH()
 
   if (rfix) delete [] rfix;
 
-  if (tcomputeflag) {
-    modify->delete_compute(id_temp);
-    delete [] id_temp;
-  }
+  if (tcomputeflag) modify->delete_compute(id_temp);
+  delete [] id_temp;
 
   // delete pressure if fix created it
 
@@ -1265,7 +1266,6 @@ int FixRigidNH::modify_param(int narg, char **arg)
 {
   if (strcmp(arg[0],"temp") == 0) {
     if (narg < 2) error->all(FLERR,"Illegal fix_modify command");
-    if (!pstat_flag) error->all(FLERR,"Illegal fix_modify command");
     if (tcomputeflag) {
       modify->delete_compute(id_temp);
       tcomputeflag = 0;
diff --git a/src/RIGID/fix_rigid_nh.h b/src/RIGID/fix_rigid_nh.h
index 684579b8af..08208e5aac 100644
--- a/src/RIGID/fix_rigid_nh.h
+++ b/src/RIGID/fix_rigid_nh.h
@@ -69,7 +69,7 @@ class FixRigidNH : public FixRigid {
 
   char *id_temp,*id_press;
   class Compute *temperature,*pressure;
-  int tcomputeflag,pcomputeflag;
+  int tcomputeflag,pcomputeflag;      // 1 = compute was created by fix. 0 = external
 
   void couple();
   void remap();
diff --git a/src/RIGID/fix_rigid_nh_small.cpp b/src/RIGID/fix_rigid_nh_small.cpp
index 5708bb6602..d8ec174f72 100644
--- a/src/RIGID/fix_rigid_nh_small.cpp
+++ b/src/RIGID/fix_rigid_nh_small.cpp
@@ -163,6 +163,9 @@ FixRigidNHSmall::FixRigidNHSmall(LAMMPS *lmp, int narg, char **arg) :
 
   tcomputeflag = 0;
   pcomputeflag = 0;
+
+  id_temp = NULL;
+  id_press = NULL;
 }
 
 /* ---------------------------------------------------------------------- */
@@ -176,10 +179,8 @@ FixRigidNHSmall::~FixRigidNHSmall()
 
   if (rfix) delete [] rfix;
 
-  if (tcomputeflag) {
-    modify->delete_compute(id_temp);
-    delete [] id_temp;
-  }
+  if (tcomputeflag) modify->delete_compute(id_temp);
+  delete [] id_temp;
 
   // delete pressure if fix created it
 
@@ -1374,7 +1375,6 @@ int FixRigidNHSmall::modify_param(int narg, char **arg)
 {
   if (strcmp(arg[0],"temp") == 0) {
     if (narg < 2) error->all(FLERR,"Illegal fix_modify command");
-    if (!pstat_flag) error->all(FLERR,"Illegal fix_modify command");
     if (tcomputeflag) {
       modify->delete_compute(id_temp);
       tcomputeflag = 0;
diff --git a/src/RIGID/fix_rigid_nh_small.h b/src/RIGID/fix_rigid_nh_small.h
index f771b8c41b..07510a59e3 100644
--- a/src/RIGID/fix_rigid_nh_small.h
+++ b/src/RIGID/fix_rigid_nh_small.h
@@ -68,7 +68,7 @@ class FixRigidNHSmall : public FixRigidSmall {
 
   char *id_temp,*id_press;
   class Compute *temperature,*pressure;
-  int tcomputeflag,pcomputeflag;
+  int tcomputeflag,pcomputeflag;      // 1 = compute was created by fix. 0 = external
 
   void couple();
   void remap();
diff --git a/src/SHOCK/fix_nphug.cpp b/src/SHOCK/fix_nphug.cpp
index 480b667254..7fc0f8a381 100644
--- a/src/SHOCK/fix_nphug.cpp
+++ b/src/SHOCK/fix_nphug.cpp
@@ -135,7 +135,7 @@ FixNPHug::FixNPHug(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -153,7 +153,7 @@ FixNPHug::FixNPHug(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 
   // create a new compute potential energy compute
 
diff --git a/src/USER-EFF/fix_nph_eff.cpp b/src/USER-EFF/fix_nph_eff.cpp
index dc6bfe20d5..0fe8c8e6db 100644
--- a/src/USER-EFF/fix_nph_eff.cpp
+++ b/src/USER-EFF/fix_nph_eff.cpp
@@ -46,7 +46,7 @@ FixNPHEff::FixNPHEff(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPHEff::FixNPHEff(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-EFF/fix_npt_eff.cpp b/src/USER-EFF/fix_npt_eff.cpp
index 36a6f87cba..02f09839b1 100644
--- a/src/USER-EFF/fix_npt_eff.cpp
+++ b/src/USER-EFF/fix_npt_eff.cpp
@@ -46,7 +46,7 @@ FixNPTEff::FixNPTEff(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTEff::FixNPTEff(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-EFF/fix_nvt_eff.cpp b/src/USER-EFF/fix_nvt_eff.cpp
index 36a9ff3293..ab82f9e0f8 100644
--- a/src/USER-EFF/fix_nvt_eff.cpp
+++ b/src/USER-EFF/fix_nvt_eff.cpp
@@ -46,5 +46,5 @@ FixNVTEff::FixNVTEff(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/USER-EFF/fix_nvt_sllod_eff.cpp b/src/USER-EFF/fix_nvt_sllod_eff.cpp
index 1f6dea658f..1b4ec1f3fb 100644
--- a/src/USER-EFF/fix_nvt_sllod_eff.cpp
+++ b/src/USER-EFF/fix_nvt_sllod_eff.cpp
@@ -58,7 +58,7 @@ FixNVTSllodEff::FixNVTSllodEff(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/USER-INTEL/fix_npt_intel.cpp b/src/USER-INTEL/fix_npt_intel.cpp
index 150464413e..2bfbd5e735 100644
--- a/src/USER-INTEL/fix_npt_intel.cpp
+++ b/src/USER-INTEL/fix_npt_intel.cpp
@@ -46,7 +46,7 @@ FixNPTIntel::FixNPTIntel(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTIntel::FixNPTIntel(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-INTEL/fix_nvt_intel.cpp b/src/USER-INTEL/fix_nvt_intel.cpp
index 65854b07a8..3fe712c9ab 100644
--- a/src/USER-INTEL/fix_nvt_intel.cpp
+++ b/src/USER-INTEL/fix_nvt_intel.cpp
@@ -45,6 +45,6 @@ FixNVTIntel::FixNVTIntel(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
 
diff --git a/src/USER-INTEL/fix_nvt_sllod_intel.cpp b/src/USER-INTEL/fix_nvt_sllod_intel.cpp
index 5505abb9ce..bab748ad74 100644
--- a/src/USER-INTEL/fix_nvt_sllod_intel.cpp
+++ b/src/USER-INTEL/fix_nvt_sllod_intel.cpp
@@ -59,7 +59,7 @@ FixNVTSllodIntel::FixNVTSllodIntel(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/USER-OMP/fix_nph_asphere_omp.cpp b/src/USER-OMP/fix_nph_asphere_omp.cpp
index 3e0a6c9df0..dfcbc87e6f 100644
--- a/src/USER-OMP/fix_nph_asphere_omp.cpp
+++ b/src/USER-OMP/fix_nph_asphere_omp.cpp
@@ -46,7 +46,7 @@ FixNPHAsphereOMP::FixNPHAsphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPHAsphereOMP::FixNPHAsphereOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nph_omp.cpp b/src/USER-OMP/fix_nph_omp.cpp
index be21da2eed..f2a4e66f55 100644
--- a/src/USER-OMP/fix_nph_omp.cpp
+++ b/src/USER-OMP/fix_nph_omp.cpp
@@ -46,7 +46,7 @@ FixNPHOMP::FixNPHOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPHOMP::FixNPHOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nph_sphere_omp.cpp b/src/USER-OMP/fix_nph_sphere_omp.cpp
index a5626f9d1c..670009de2f 100644
--- a/src/USER-OMP/fix_nph_sphere_omp.cpp
+++ b/src/USER-OMP/fix_nph_sphere_omp.cpp
@@ -46,7 +46,7 @@ FixNPHSphereOMP::FixNPHSphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPHSphereOMP::FixNPHSphereOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nphug_omp.cpp b/src/USER-OMP/fix_nphug_omp.cpp
index 7721781769..b652cf563a 100644
--- a/src/USER-OMP/fix_nphug_omp.cpp
+++ b/src/USER-OMP/fix_nphug_omp.cpp
@@ -135,7 +135,7 @@ FixNPHugOMP::FixNPHugOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -153,7 +153,7 @@ FixNPHugOMP::FixNPHugOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 
   // create a new compute potential energy compute
 
diff --git a/src/USER-OMP/fix_npt_asphere_omp.cpp b/src/USER-OMP/fix_npt_asphere_omp.cpp
index 00bafe661a..1db62d40c0 100644
--- a/src/USER-OMP/fix_npt_asphere_omp.cpp
+++ b/src/USER-OMP/fix_npt_asphere_omp.cpp
@@ -46,7 +46,7 @@ FixNPTAsphereOMP::FixNPTAsphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTAsphereOMP::FixNPTAsphereOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_npt_omp.cpp b/src/USER-OMP/fix_npt_omp.cpp
index c4af48542a..5610f62f36 100644
--- a/src/USER-OMP/fix_npt_omp.cpp
+++ b/src/USER-OMP/fix_npt_omp.cpp
@@ -46,7 +46,7 @@ FixNPTOMP::FixNPTOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTOMP::FixNPTOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_npt_sphere_omp.cpp b/src/USER-OMP/fix_npt_sphere_omp.cpp
index 6baee93cb4..d71d1380b9 100644
--- a/src/USER-OMP/fix_npt_sphere_omp.cpp
+++ b/src/USER-OMP/fix_npt_sphere_omp.cpp
@@ -46,7 +46,7 @@ FixNPTSphereOMP::FixNPTSphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTSphereOMP::FixNPTSphereOMP(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nvt_asphere_omp.cpp b/src/USER-OMP/fix_nvt_asphere_omp.cpp
index 23cc2e9581..bb1e784a37 100644
--- a/src/USER-OMP/fix_nvt_asphere_omp.cpp
+++ b/src/USER-OMP/fix_nvt_asphere_omp.cpp
@@ -45,5 +45,5 @@ FixNVTAsphereOMP::FixNVTAsphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nvt_omp.cpp b/src/USER-OMP/fix_nvt_omp.cpp
index 18d02bff4d..f8f3c15b76 100644
--- a/src/USER-OMP/fix_nvt_omp.cpp
+++ b/src/USER-OMP/fix_nvt_omp.cpp
@@ -45,5 +45,5 @@ FixNVTOMP::FixNVTOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nvt_sllod_omp.cpp b/src/USER-OMP/fix_nvt_sllod_omp.cpp
index 8105e831f7..bd704148a5 100644
--- a/src/USER-OMP/fix_nvt_sllod_omp.cpp
+++ b/src/USER-OMP/fix_nvt_sllod_omp.cpp
@@ -65,7 +65,7 @@ FixNVTSllodOMP::FixNVTSllodOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/USER-OMP/fix_nvt_sphere_omp.cpp b/src/USER-OMP/fix_nvt_sphere_omp.cpp
index 6db9ad849a..22eda99883 100644
--- a/src/USER-OMP/fix_nvt_sphere_omp.cpp
+++ b/src/USER-OMP/fix_nvt_sphere_omp.cpp
@@ -45,5 +45,5 @@ FixNVTSphereOMP::FixNVTSphereOMP(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/USER-REAXC/pair_reax_c.cpp b/src/USER-REAXC/pair_reax_c.cpp
index 59b39d4534..b1a14f84e6 100644
--- a/src/USER-REAXC/pair_reax_c.cpp
+++ b/src/USER-REAXC/pair_reax_c.cpp
@@ -386,7 +386,6 @@ void PairReaxC::init_style( )
     delete [] fixarg;
     fix_reax = (FixReaxC *) modify->fix[modify->nfix-1];
   }
-
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/USER-TALLY/compute_force_tally.cpp b/src/USER-TALLY/compute_force_tally.cpp
index 90464d7949..e9ecedd5ab 100644
--- a/src/USER-TALLY/compute_force_tally.cpp
+++ b/src/USER-TALLY/compute_force_tally.cpp
@@ -56,6 +56,7 @@ ComputeForceTally::ComputeForceTally(LAMMPS *lmp, int narg, char **arg) :
 ComputeForceTally::~ComputeForceTally()
 {
   if (force && force->pair) force->pair->del_tally_callback(this);
+  memory->destroy(fatom);
   delete[] vector;
 }
 
diff --git a/src/USER-TALLY/compute_pe_tally.cpp b/src/USER-TALLY/compute_pe_tally.cpp
index f18a58e44e..68c00b6d2e 100644
--- a/src/USER-TALLY/compute_pe_tally.cpp
+++ b/src/USER-TALLY/compute_pe_tally.cpp
@@ -55,6 +55,7 @@ ComputePETally::ComputePETally(LAMMPS *lmp, int narg, char **arg) :
 ComputePETally::~ComputePETally()
 {
   if (force && force->pair) force->pair->del_tally_callback(this);
+  memory->destroy(eatom);
   delete[] vector;
 }
 
diff --git a/src/USER-TALLY/compute_stress_tally.cpp b/src/USER-TALLY/compute_stress_tally.cpp
index 2a5f522636..2575bd372a 100644
--- a/src/USER-TALLY/compute_stress_tally.cpp
+++ b/src/USER-TALLY/compute_stress_tally.cpp
@@ -56,6 +56,7 @@ ComputeStressTally::ComputeStressTally(LAMMPS *lmp, int narg, char **arg) :
 ComputeStressTally::~ComputeStressTally()
 {
   if (force && force->pair) force->pair->del_tally_callback(this);
+  memory->destroy(stress);
   delete[] vector;
 }
 
diff --git a/src/comm.cpp b/src/comm.cpp
index 825460720d..f29d1bf7df 100644
--- a/src/comm.cpp
+++ b/src/comm.cpp
@@ -688,6 +688,10 @@ void Comm::ring(int n, int nper, void *inbuf, int messtag,
   int maxbytes;
   MPI_Allreduce(&nbytes,&maxbytes,1,MPI_INT,MPI_MAX,world);
 
+  // no need to communicate without data
+
+  if (maxbytes == 0) return;
+
   char *buf,*bufcopy;
   memory->create(buf,maxbytes,"comm:buf");
   memory->create(bufcopy,maxbytes,"comm:bufcopy");
diff --git a/src/compute_angmom_chunk.cpp b/src/compute_angmom_chunk.cpp
index 93a843ac31..5e88f5bc25 100644
--- a/src/compute_angmom_chunk.cpp
+++ b/src/compute_angmom_chunk.cpp
@@ -136,9 +136,11 @@ void ComputeAngmomChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // compute angmom for each chunk
diff --git a/src/compute_dipole_chunk.cpp b/src/compute_dipole_chunk.cpp
index 449fb002b6..cb618055f6 100644
--- a/src/compute_dipole_chunk.cpp
+++ b/src/compute_dipole_chunk.cpp
@@ -159,10 +159,11 @@ void ComputeDipoleChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    if (masstotal[i] == 0.0) masstotal[i] = 1.0;
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // compute dipole for each chunk
diff --git a/src/compute_gyration.cpp b/src/compute_gyration.cpp
index 0c1c58a4fd..7f06df9103 100644
--- a/src/compute_gyration.cpp
+++ b/src/compute_gyration.cpp
@@ -109,6 +109,7 @@ void ComputeGyration::compute_vector()
     }
   MPI_Allreduce(rg,vector,6,MPI_DOUBLE,MPI_SUM,world);
 
-  if (masstotal == 0.0) return;
-  for (int i = 0; i < 6; i++) vector[i] = vector[i]/masstotal;
+  if (masstotal > 0.0) 
+    for (int i = 0; i < 6; i++)
+      vector[i] /= masstotal;
 }
diff --git a/src/compute_gyration_chunk.cpp b/src/compute_gyration_chunk.cpp
index e006a82299..58fe33bc3c 100644
--- a/src/compute_gyration_chunk.cpp
+++ b/src/compute_gyration_chunk.cpp
@@ -143,7 +143,8 @@ void ComputeGyrationChunk::compute_vector()
   MPI_Allreduce(rg,rgall,nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++)
-    rgall[i] = sqrt(rgall[i]/masstotal[i]);
+    if (masstotal[i] > 0.0)
+      rgall[i] = sqrt(rgall[i]/masstotal[i]);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -191,9 +192,12 @@ void ComputeGyrationChunk::compute_array()
   if (nchunk)
     MPI_Allreduce(&rgt[0][0],&rgtall[0][0],nchunk*6,MPI_DOUBLE,MPI_SUM,world);
 
-  for (i = 0; i < nchunk; i++)
-    for (j = 0; j < 6; j++)
-      rgtall[i][j] = rgtall[i][j]/masstotal[i];
+  for (i = 0; i < nchunk; i++) {
+    if (masstotal[i] > 0.0) {
+      for (j = 0; j < 6; j++)
+        rgtall[i][j] = rgtall[i][j]/masstotal[i];
+    }
+  }
 }
 
 
@@ -253,9 +257,11 @@ void ComputeGyrationChunk::com_chunk()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 }
 
diff --git a/src/compute_inertia_chunk.cpp b/src/compute_inertia_chunk.cpp
index 33660b839f..c4e83fa4a1 100644
--- a/src/compute_inertia_chunk.cpp
+++ b/src/compute_inertia_chunk.cpp
@@ -136,9 +136,11 @@ void ComputeInertiaChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // compute inertia tensor for each chunk
diff --git a/src/compute_msd_chunk.cpp b/src/compute_msd_chunk.cpp
index 9d9ddcb3bd..30eee1d64a 100644
--- a/src/compute_msd_chunk.cpp
+++ b/src/compute_msd_chunk.cpp
@@ -201,9 +201,11 @@ void ComputeMSDChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // MSD is difference between current and initial COM
diff --git a/src/compute_omega_chunk.cpp b/src/compute_omega_chunk.cpp
index c437dd66b3..54e0b8f906 100644
--- a/src/compute_omega_chunk.cpp
+++ b/src/compute_omega_chunk.cpp
@@ -138,9 +138,11 @@ void ComputeOmegaChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // compute inertia tensor for each chunk
diff --git a/src/compute_temp_chunk.cpp b/src/compute_temp_chunk.cpp
index 5a5853514f..87d6e11864 100644
--- a/src/compute_temp_chunk.cpp
+++ b/src/compute_temp_chunk.cpp
@@ -472,9 +472,13 @@ void ComputeTempChunk::vcm_compute()
   MPI_Allreduce(massproc,masstotal,nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (i = 0; i < nchunk; i++) {
-    vcmall[i][0] /= masstotal[i];
-    vcmall[i][1] /= masstotal[i];
-    vcmall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      vcmall[i][0] /= masstotal[i];
+      vcmall[i][1] /= masstotal[i];
+      vcmall[i][2] /= masstotal[i];
+    } else {
+      vcmall[i][0] = vcmall[i][1] = vcmall[i][2] = 0.0;
+    }
   }
 }
 
@@ -689,7 +693,7 @@ void ComputeTempChunk::internal(int icol)
 
 void ComputeTempChunk::remove_bias(int i, double *v)
 {
-  int index = cchunk->ichunk[i];
+  int index = cchunk->ichunk[i]-1;
   if (index < 0) return;
   v[0] -= vcmall[index][0];
   v[1] -= vcmall[index][1];
@@ -711,11 +715,11 @@ void ComputeTempChunk::remove_bias_all()
 
   for (int i = 0; i < nlocal; i++)
     if (mask[i] & groupbit) {
-      index = ichunk[i];
+      index = ichunk[i]-1;
       if (index < 0) continue;
-      v[i][0] -= vbias[0];
-      v[i][1] -= vbias[1];
-      v[i][2] -= vbias[2];
+      v[i][0] -= vcmall[index][0];
+      v[i][1] -= vcmall[index][1];
+      v[i][2] -= vcmall[index][2];
     }
 }
 
@@ -726,7 +730,7 @@ void ComputeTempChunk::remove_bias_all()
 
 void ComputeTempChunk::restore_bias(int i, double *v)
 {
-  int index = cchunk->ichunk[i];
+  int index = cchunk->ichunk[i]-1;
   if (index < 0) return;
   v[0] += vcmall[index][0];
   v[1] += vcmall[index][1];
@@ -749,11 +753,11 @@ void ComputeTempChunk::restore_bias_all()
 
   for (int i = 0; i < nlocal; i++)
     if (mask[i] & groupbit) {
-      index = ichunk[i];
+      index = ichunk[i]-1;
       if (index < 0) continue;
-      v[i][0] += vbias[0];
-      v[i][1] += vbias[1];
-      v[i][2] += vbias[2];
+      v[i][0] += vcmall[index][0];
+      v[i][1] += vcmall[index][1];
+      v[i][2] += vcmall[index][2];
     }
 }
 
diff --git a/src/compute_temp_region.cpp b/src/compute_temp_region.cpp
index 158c93b2fb..33e07bfb1e 100644
--- a/src/compute_temp_region.cpp
+++ b/src/compute_temp_region.cpp
@@ -209,7 +209,7 @@ void ComputeTempRegion::remove_bias_all()
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
 
-  if (nlocal > maxbias) {
+  if (atom->nmax > maxbias) {
     memory->destroy(vbiasall);
     maxbias = atom->nmax;
     memory->create(vbiasall,maxbias,3,"temp/region:vbiasall");
diff --git a/src/compute_torque_chunk.cpp b/src/compute_torque_chunk.cpp
index 41ae0c628c..5462debcfc 100644
--- a/src/compute_torque_chunk.cpp
+++ b/src/compute_torque_chunk.cpp
@@ -136,9 +136,11 @@ void ComputeTorqueChunk::compute_array()
   MPI_Allreduce(&com[0][0],&comall[0][0],3*nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    comall[i][0] /= masstotal[i];
-    comall[i][1] /= masstotal[i];
-    comall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      comall[i][0] /= masstotal[i];
+      comall[i][1] /= masstotal[i];
+      comall[i][2] /= masstotal[i];
+    }
   }
 
   // compute torque on each chunk
diff --git a/src/compute_vcm_chunk.cpp b/src/compute_vcm_chunk.cpp
index a3751fa13a..cd864b2aa8 100644
--- a/src/compute_vcm_chunk.cpp
+++ b/src/compute_vcm_chunk.cpp
@@ -146,9 +146,11 @@ void ComputeVCMChunk::compute_array()
     MPI_Allreduce(massproc,masstotal,nchunk,MPI_DOUBLE,MPI_SUM,world);
 
   for (int i = 0; i < nchunk; i++) {
-    vcmall[i][0] /= masstotal[i];
-    vcmall[i][1] /= masstotal[i];
-    vcmall[i][2] /= masstotal[i];
+    if (masstotal[i] > 0.0) {
+      vcmall[i][0] /= masstotal[i];
+      vcmall[i][1] /= masstotal[i];
+      vcmall[i][2] /= masstotal[i];
+    } else vcmall[i][0] = vcmall[i][1] = vcmall[i][2] = 0.0;
   }
 }
 
diff --git a/src/fix_deprecated.cpp b/src/fix_deprecated.cpp
index 8139a14d9d..9c0b6686d1 100644
--- a/src/fix_deprecated.cpp
+++ b/src/fix_deprecated.cpp
@@ -34,8 +34,8 @@ FixDeprecated::FixDeprecated(LAMMPS *lmp, int narg, char **arg) :
     "  dim, origin, delta, region, bound, discard, units\n\n";
 
     if (comm->me == 0) {
-      if (screen) fprintf(screen,message);
-      if (logfile) fprintf(logfile,message);
+      if (screen) fputs(message,screen);
+      if (logfile) fputs(message,logfile);
     }
   }
   error->all(FLERR,"This fix command has been removed from LAMMPS");
diff --git a/src/fix_heat.cpp b/src/fix_heat.cpp
index 0609d45efb..5da405ae3f 100644
--- a/src/fix_heat.cpp
+++ b/src/fix_heat.cpp
@@ -133,6 +133,8 @@ void FixHeat::init()
   if (group->count(igroup) == 0)
     error->all(FLERR,"Fix heat group has no atoms");
   masstotal = group->mass(igroup);
+  if (masstotal <= 0.0)
+    error->all(FLERR,"Fix heat group has invalid mass");
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/fix_nh.cpp b/src/fix_nh.cpp
index b300fd2d46..2f1081216b 100644
--- a/src/fix_nh.cpp
+++ b/src/fix_nh.cpp
@@ -80,6 +80,11 @@ FixNH::FixNH(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
   flipflag = 1;
   dipole_flag = 0;
 
+  tcomputeflag = 0;
+  pcomputeflag = 0;
+  id_temp = NULL;
+  id_press = NULL;
+
   // turn on tilt factor scaling, whenever applicable
 
   dimension = domain->dimension;
@@ -558,7 +563,7 @@ FixNH::~FixNH()
 
   // delete temperature and pressure if fix created them
 
-  if (tflag) modify->delete_compute(id_temp);
+  if (tcomputeflag) modify->delete_compute(id_temp);
   delete [] id_temp;
 
   if (tstat_flag) {
@@ -569,7 +574,7 @@ FixNH::~FixNH()
   }
 
   if (pstat_flag) {
-    if (pflag) modify->delete_compute(id_press);
+    if (pcomputeflag) modify->delete_compute(id_press);
     delete [] id_press;
     if (mpchain) {
       delete [] etap;
@@ -1347,9 +1352,9 @@ int FixNH::modify_param(int narg, char **arg)
 {
   if (strcmp(arg[0],"temp") == 0) {
     if (narg < 2) error->all(FLERR,"Illegal fix_modify command");
-    if (tflag) {
+    if (tcomputeflag) {
       modify->delete_compute(id_temp);
-      tflag = 0;
+      tcomputeflag = 0;
     }
     delete [] id_temp;
     int n = strlen(arg[1]) + 1;
@@ -1381,9 +1386,9 @@ int FixNH::modify_param(int narg, char **arg)
   } else if (strcmp(arg[0],"press") == 0) {
     if (narg < 2) error->all(FLERR,"Illegal fix_modify command");
     if (!pstat_flag) error->all(FLERR,"Illegal fix_modify command");
-    if (pflag) {
+    if (pcomputeflag) {
       modify->delete_compute(id_press);
-      pflag = 0;
+      pcomputeflag = 0;
     }
     delete [] id_press;
     int n = strlen(arg[1]) + 1;
diff --git a/src/fix_nh.h b/src/fix_nh.h
index 7227a22968..e468d49817 100644
--- a/src/fix_nh.h
+++ b/src/fix_nh.h
@@ -76,7 +76,7 @@ class FixNH : public Fix {
 
   char *id_temp,*id_press;
   class Compute *temperature,*pressure;
-  int tflag,pflag;
+  int tcomputeflag,pcomputeflag;   // 1 = compute was created by fix. 0 = external
 
   double *eta,*eta_dot;            // chain thermostat for particles
   double *eta_dotdot;
diff --git a/src/fix_nph.cpp b/src/fix_nph.cpp
index 6f3678ed3a..a331a07d24 100644
--- a/src/fix_nph.cpp
+++ b/src/fix_nph.cpp
@@ -46,7 +46,7 @@ FixNPH::FixNPH(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPH::FixNPH(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/fix_nph_sphere.cpp b/src/fix_nph_sphere.cpp
index 93d9bf8af2..852234074f 100644
--- a/src/fix_nph_sphere.cpp
+++ b/src/fix_nph_sphere.cpp
@@ -46,7 +46,7 @@ FixNPHSphere::FixNPHSphere(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPHSphere::FixNPHSphere(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/fix_npt.cpp b/src/fix_npt.cpp
index 0326c06c77..e14200f6a2 100644
--- a/src/fix_npt.cpp
+++ b/src/fix_npt.cpp
@@ -46,7 +46,7 @@ FixNPT::FixNPT(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPT::FixNPT(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/fix_npt_sphere.cpp b/src/fix_npt_sphere.cpp
index 6e7c074d5e..d3773e0d17 100644
--- a/src/fix_npt_sphere.cpp
+++ b/src/fix_npt_sphere.cpp
@@ -46,7 +46,7 @@ FixNPTSphere::FixNPTSphere(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
@@ -64,5 +64,5 @@ FixNPTSphere::FixNPTSphere(LAMMPS *lmp, int narg, char **arg) :
   newarg[3] = id_temp;
   modify->add_compute(4,newarg);
   delete [] newarg;
-  pflag = 1;
+  pcomputeflag = 1;
 }
diff --git a/src/fix_nvt.cpp b/src/fix_nvt.cpp
index a86f46c3b5..35ee085da1 100644
--- a/src/fix_nvt.cpp
+++ b/src/fix_nvt.cpp
@@ -45,5 +45,5 @@ FixNVT::FixNVT(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/fix_nvt_sllod.cpp b/src/fix_nvt_sllod.cpp
index 8257afae05..87e86f2351 100644
--- a/src/fix_nvt_sllod.cpp
+++ b/src/fix_nvt_sllod.cpp
@@ -63,7 +63,7 @@ FixNVTSllod::FixNVTSllod(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/fix_nvt_sphere.cpp b/src/fix_nvt_sphere.cpp
index c886935f12..b65b3adfae 100644
--- a/src/fix_nvt_sphere.cpp
+++ b/src/fix_nvt_sphere.cpp
@@ -45,5 +45,5 @@ FixNVTSphere::FixNVTSphere(LAMMPS *lmp, int narg, char **arg) :
 
   modify->add_compute(3,newarg);
   delete [] newarg;
-  tflag = 1;
+  tcomputeflag = 1;
 }
diff --git a/src/fix_recenter.cpp b/src/fix_recenter.cpp
index 7d30c2f865..e10edcb2d9 100644
--- a/src/fix_recenter.cpp
+++ b/src/fix_recenter.cpp
@@ -52,6 +52,7 @@ FixRecenter::FixRecenter(LAMMPS *lmp, int narg, char **arg) :
   extscalar = 1;
   extvector = 1;
   global_freq = 1;
+  dynamic_group_allow = 1;
 
 /* ---------------------------------------------------------------------- */
 
@@ -186,6 +187,9 @@ void FixRecenter::initial_integrate(int vflag)
   // current COM
 
   double xcm[3];
+  if (group->dynamic[igroup])
+    masstotal = group->mass(igroup);
+
   group->xcm(igroup,masstotal,xcm);
 
   // shift coords by difference between actual COM and requested COM
diff --git a/src/fix_spring.cpp b/src/fix_spring.cpp
index ddc161e50d..fb2b21b71d 100644
--- a/src/fix_spring.cpp
+++ b/src/fix_spring.cpp
@@ -47,6 +47,7 @@ FixSpring::FixSpring(LAMMPS *lmp, int narg, char **arg) :
   global_freq = 1;
   extscalar = 1;
   extvector = 1;
+  dynamic_group_allow = 1;
 
   group2 = NULL;
 
@@ -166,6 +167,10 @@ void FixSpring::post_force(int vflag)
 void FixSpring::spring_tether()
 {
   double xcm[3];
+
+  if (group->dynamic[igroup])
+    masstotal = group->mass(igroup);
+
   group->xcm(igroup,masstotal,xcm);
 
   // fx,fy,fz = components of k * (r-r0) / masstotal
@@ -192,9 +197,11 @@ void FixSpring::spring_tether()
   if (dr < 0.0) ftotal[3] = -ftotal[3];
   espring = 0.5*k_spring * dr*dr;
 
-  fx /= masstotal;
-  fy /= masstotal;
-  fz /= masstotal;
+  if (masstotal > 0.0) {
+    fx /= masstotal;
+    fy /= masstotal;
+    fz /= masstotal;
+  }
 
   // apply restoring force to atoms in group
 
@@ -231,6 +238,13 @@ void FixSpring::spring_tether()
 void FixSpring::spring_couple()
 {
   double xcm[3],xcm2[3];
+
+  if (group->dynamic[igroup])
+    masstotal = group->mass(igroup);
+
+  if (group->dynamic[igroup2])
+    masstotal2 = group->mass(igroup2);
+
   group->xcm(igroup,masstotal,xcm);
   group->xcm(igroup2,masstotal2,xcm2);
 
@@ -259,12 +273,16 @@ void FixSpring::spring_couple()
   if (dr < 0.0) ftotal[3] = -ftotal[3];
   espring = 0.5*k_spring * dr*dr;
 
-  fx2 = fx/masstotal2;
-  fy2 = fy/masstotal2;
-  fz2 = fz/masstotal2;
-  fx /= masstotal;
-  fy /= masstotal;
-  fz /= masstotal;
+  if (masstotal2 > 0.0) {
+    fx2 = fx/masstotal2;
+    fy2 = fy/masstotal2;
+    fz2 = fz/masstotal2;
+  }
+  if (masstotal > 0.0) {
+    fx /= masstotal;
+    fy /= masstotal;
+    fz /= masstotal;
+  }
 
   // apply restoring force to atoms in group
   // f = -k*(r-r0)*mass/masstotal
diff --git a/src/fix_spring_rg.cpp b/src/fix_spring_rg.cpp
index 5e267340c1..4145e01047 100644
--- a/src/fix_spring_rg.cpp
+++ b/src/fix_spring_rg.cpp
@@ -42,6 +42,8 @@ FixSpringRG::FixSpringRG(LAMMPS *lmp, int narg, char **arg) :
   rg0_flag = 0;
   if (strcmp(arg[4],"NULL") == 0) rg0_flag = 1;
   else rg0 = force->numeric(FLERR,arg[4]);
+
+  dynamic_group_allow = 1;
 }
 
 /* ---------------------------------------------------------------------- */
@@ -94,6 +96,8 @@ void FixSpringRG::post_force(int vflag)
   // compute current Rg and center-of-mass
 
   double xcm[3];
+  if (group->dynamic[igroup])
+    masstotal = group->mass(igroup);
   group->xcm(igroup,masstotal,xcm);
   double rg = group->gyration(igroup,masstotal,xcm);
 
@@ -108,6 +112,7 @@ void FixSpringRG::post_force(int vflag)
   int *type = atom->type;
   imageint *image = atom->image;
   double *mass = atom->mass;
+  double *rmass = atom->rmass;
   int nlocal = atom->nlocal;
 
   double massfrac;
@@ -120,10 +125,14 @@ void FixSpringRG::post_force(int vflag)
       dy = unwrap[1] - xcm[1];
       dz = unwrap[2] - xcm[2];
       term1 = 2.0 * k * (1.0 - rg0/rg);
-      massfrac = mass[type[i]]/masstotal;
-      f[i][0] -= term1*dx*massfrac;
-      f[i][1] -= term1*dy*massfrac;
-      f[i][2] -= term1*dz*massfrac;
+      if (masstotal > 0.0) {
+        if (rmass) massfrac = rmass[i]/masstotal;
+        else  massfrac = mass[type[i]]/masstotal;
+
+        f[i][0] -= term1*dx*massfrac;
+        f[i][1] -= term1*dy*massfrac;
+        f[i][2] -= term1*dz*massfrac;
+      }
     }
 }
 
diff --git a/src/fix_tmd.cpp b/src/fix_tmd.cpp
index 4be97a816e..d326685368 100644
--- a/src/fix_tmd.cpp
+++ b/src/fix_tmd.cpp
@@ -85,6 +85,8 @@ FixTMD::FixTMD(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
   }
 
   masstotal = group->mass(igroup);
+  if (masstotal == 0.0)
+    error->all(FLERR,"Cannot use fix TMD on massless group");
 
   // rho_start = initial rho
   // xold = initial x or 0.0 if not in group
@@ -155,10 +157,7 @@ void FixTMD::init()
   int flag = 0;
   for (int i = 0; i < modify->nfix; i++) {
     if (strcmp(modify->fix[i]->style,"tmd") == 0) flag = 1;
-    if (flag && strcmp(modify->fix[i]->style,"nve") == 0) flag = 2;
-    if (flag && strcmp(modify->fix[i]->style,"nvt") == 0) flag = 2;
-    if (flag && strcmp(modify->fix[i]->style,"npt") == 0) flag = 2;
-    if (flag && strcmp(modify->fix[i]->style,"nph") == 0) flag = 2;
+    if (flag && modify->fix[i]->time_integrate) flag = 2;
   }
   if (flag == 2) error->all(FLERR,"Fix tmd must come after integration fixes");
 
diff --git a/src/lattice.cpp b/src/lattice.cpp
index e851760792..484ce27972 100644
--- a/src/lattice.cpp
+++ b/src/lattice.cpp
@@ -53,7 +53,16 @@ Lattice::Lattice(LAMMPS *lmp, int narg, char **arg) : Pointers(lmp)
 
   if (style == NONE) {
     if (narg != 2) error->all(FLERR,"Illegal lattice command");
-    xlattice = ylattice = zlattice = force->numeric(FLERR,arg[1]);
+
+    // Domain defines a default lattice of style "none" with
+    // spacing 1.0 before the force class is initialized, so
+    // we have to fall back to using atof() in that case.
+
+    if (force)
+      xlattice = ylattice = zlattice = force->numeric(FLERR,arg[1]);
+    else
+      xlattice = ylattice = zlattice = atof(arg[1]);
+
     if (xlattice <= 0.0) error->all(FLERR,"Illegal lattice command");
     return;
   }
diff --git a/src/molecule.cpp b/src/molecule.cpp
index 99b5718133..91557b32ba 100644
--- a/src/molecule.cpp
+++ b/src/molecule.cpp
@@ -245,9 +245,11 @@ void Molecule::compute_com()
       com[1] += x[i][1]*onemass;
       com[2] += x[i][2]*onemass;
     }
-    com[0] /= masstotal;
-    com[1] /= masstotal;
-    com[2] /= masstotal;
+    if (masstotal > 0.0) {
+      com[0] /= masstotal;
+      com[1] /= masstotal;
+      com[2] /= masstotal;
+    }
   }
 
   memory->destroy(dxcom);
diff --git a/src/replicate.cpp b/src/replicate.cpp
index 941ec32492..e2ed718f65 100644
--- a/src/replicate.cpp
+++ b/src/replicate.cpp
@@ -116,9 +116,9 @@ void Replicate::command(int narg, char **arg)
   // also set atomKK for Kokkos version of Atom class
 
   Atom *old = atom;
-  if (lmp->kokkos) atom = new AtomKokkos(lmp);
+  atomKK = NULL;
+  if (lmp->kokkos) atom = atomKK = new AtomKokkos(lmp);
   else atom = new Atom(lmp);
-  atomKK = (AtomKokkos*) atom;
 
   atom->settings(old);
   atom->create_avec(old->atom_style,old->avec->nargcopy,old->avec->argcopy,0);