Update gcmc to have a max and min

src/MC/fix_gcmc.cpp

@@ -272,6 +272,8 @@ void FixGCMC::options(int narg, char **arg)
   tfac_insert = 1.0;
   overlap_cutoffsq = 0.0;
   overlap_flag = 0;
+  min_ngas = -1;
+  max_ngas = -1;
 
   int iarg = 0;
   while (iarg < narg) {
@@ -391,6 +393,14 @@ void FixGCMC::options(int narg, char **arg)
       overlap_cutoffsq = rtmp*rtmp;
       overlap_flag = 1;
       iarg += 2;
+    } else if (strcmp(arg[iarg],"min") == 0) {
+      if (iarg+2 > narg) error->all(FLERR,"Illegal fix gcmc command");
+      min_ngas = force->numeric(FLERR,arg[iarg+1]);
+      iarg += 2;
+    } else if (strcmp(arg[iarg],"max") == 0) {
+      if (iarg+2 > narg) error->all(FLERR,"Illegal fix gcmc command");
+      max_ngas = force->numeric(FLERR,arg[iarg+1]);
+      iarg += 2;
     } else error->all(FLERR,"Illegal fix gcmc command");
   }
 }
@@ -897,7 +907,7 @@ void FixGCMC::attempt_atomic_deletion()
 {
   ndeletion_attempts += 1.0;
 
-  if (ngas == 0) return;
+  if (ngas == 0 || ngas == min_ngas) return;
 
   int i = pick_random_gas_atom();
 
@@ -938,6 +948,8 @@ void FixGCMC::attempt_atomic_insertion()
 
   ninsertion_attempts += 1.0;
 
+  if (ngas == max_ngas) return;
+  
   // pick coordinates for insertion point
 
   double coord[3];
@@ -1252,7 +1264,7 @@ void FixGCMC::attempt_molecule_deletion()
 {
   ndeletion_attempts += 1.0;
 
-  if (ngas == 0) return;
+  if (ngas == 0 || ngas == min_ngas) return;
 
   // work-around to avoid n=0 problem with fix rigid/nvt/small
 
@@ -1291,6 +1303,8 @@ void FixGCMC::attempt_molecule_insertion()
   double lamda[3];
   ninsertion_attempts += 1.0;
 
+  if (ngas == max_ngas) return;
+  
   double com_coord[3];
   if (regionflag) {
     int region_attempt = 0;
@@ -1574,7 +1588,7 @@ void FixGCMC::attempt_atomic_deletion_full()
 
   ndeletion_attempts += 1.0;
 
-  if (ngas == 0) return;
+  if (ngas == 0 || ngas == min_ngas) return;
 
   double energy_before = energy_stored;
 
@@ -1623,6 +1637,8 @@ void FixGCMC::attempt_atomic_insertion_full()
   double lamda[3];
   ninsertion_attempts += 1.0;
 
+  if (ngas == max_ngas) return;
+  
   double energy_before = energy_stored;
 
   double coord[3];
@@ -1918,7 +1934,7 @@ void FixGCMC::attempt_molecule_deletion_full()
 {
   ndeletion_attempts += 1.0;
 
-  if (ngas == 0) return;
+  if (ngas == 0 || ngas == min_ngas) return;
 
   // work-around to avoid n=0 problem with fix rigid/nvt/small
 
@@ -2001,6 +2017,8 @@ void FixGCMC::attempt_molecule_insertion_full()
   double lamda[3];
   ninsertion_attempts += 1.0;
 
+  if (ngas == max_ngas) return;
+
   double energy_before = energy_stored;
 
   tagint maxmol = 0;

src/MC/fix_gcmc.h

@@ -120,6 +120,8 @@ class FixGCMC : public Fix {
   imageint imagezero;
   double overlap_cutoffsq; // square distance cutoff for overlap
   int overlap_flag;
+  int max_ngas;
+  int min_ngas;
 
   double energy_intra;