adding modifications for more than one fix langevin/spin in fix nve/spin

examples/SPIN/test_problems/validation_damped_exchange/llg_exchange.py

@@ -6,7 +6,7 @@ import matplotlib.pyplot as plt
 import mpmath as mp
 
 hbar=0.658212           # Planck's constant (eV.fs/rad)
-# J0=0.05                 # per-neighbor exchange interaction (eV)
+J0=0.05                 # per-neighbor exchange interaction (eV)
 
 # exchange interaction parameters
 J1 = 11.254 # in eV 

examples/SPIN/test_problems/validation_nvt/in.spin.nvt_lattice

@@ -30,8 +30,8 @@ neighbor 	0.1 bin
 neigh_modify 	every 10 check yes delay 20
 
 fix 		1 all precession/spin zeeman 0.0 0.0 0.0 1.0
-fix             2 all langevin 200.0 200.0 1.0 48279
+fix             2 all langevin 200.0 200.0 0.1 48279
-fix 		3 all langevin/spin 0.0 0.00001 321
+fix 		3 all langevin/spin 0.0 0.0 321
 fix 		4 all nve/spin lattice moving
 timestep	0.001
 

examples/SPIN/test_problems/validation_nvt/in.spin.nvt_spin

@@ -21,16 +21,19 @@ mass		1 55.845
 set 		group all spin 2.2 0.0 0.0 1.0
 velocity 	all create 0 4928459 rot yes dist gaussian
 
-pair_style 	hybrid/overlay eam/alloy spin/exchange 3.5
+# pair_style 	hybrid/overlay eam/alloy spin/exchange 3.5
+pair_style 	hybrid/overlay eam/alloy spin/exchange 4.0 spin/neel 4.0
 pair_coeff 	* * eam/alloy Fe_Mishin2006.eam.alloy Fe
 pair_coeff 	* * spin/exchange exchange 3.4 0.1 0.2171 1.841
+pair_coeff 	* * spin/neel neel 4.0 0.02 0.0 1.841 0.0 0.0 1.0 
 
 neighbor 	0.1 bin
 neigh_modify 	every 10 check yes delay 20
 
 fix 		1 all precession/spin zeeman 0.0 0.0 0.0 1.0
-fix 		2 all langevin/spin 200.0 0.01 321
+fix             2 all langevin 0.0 0.0 0.0 48279
-fix 		3 all nve/spin lattice moving
+fix 		3 all langevin/spin 200.0 0.01 321
+fix 		4 all nve/spin lattice moving
 timestep	0.001
 
 # compute and output options

src/SPIN/fix_langevin_spin.cpp

@@ -24,6 +24,7 @@
 #include "fix_langevin_spin.h"
 #include <cmath>
 #include <cstring>
+#include "atom.h"
 #include "comm.h"
 #include "error.h"
 #include "force.h"
@@ -163,3 +164,14 @@ void FixLangevinSpin::add_temperature(double fmi[3])
   fmi[1] *= gil_factor;
   fmi[2] *= gil_factor;
 }
+
+/* ---------------------------------------------------------------------- */
+
+void FixLangevinSpin::compute_single_langevin(int i, double spi[3], double fmi[3])
+{
+  int *mask = atom->mask;
+  if (mask[i] & groupbit) {
+    if (tdamp_flag) add_tdamping(spi,fmi);
+    if (temp_flag) add_temperature(fmi);
+  }
+}

src/SPIN/fix_langevin_spin.h

@@ -26,7 +26,7 @@ namespace LAMMPS_NS {
 
 class FixLangevinSpin : public Fix {
  public:
-  int tdamp_flag,ldamp_flag,temp_flag;           // damping and temperature flags
+  int tdamp_flag,temp_flag;     // damping and temperature flags
 
   FixLangevinSpin(class LAMMPS *, int, char **);
   virtual ~FixLangevinSpin();
@@ -35,6 +35,7 @@ class FixLangevinSpin : public Fix {
   void setup(int);
   void add_tdamping(double *, double *);                 // add transverse damping
   void add_temperature(double *);                        // add temperature
+  void compute_single_langevin(int, double *, double *);
 
  protected:
   double alpha_t;               // transverse mag. damping

src/SPIN/fix_nve_spin.cpp

@@ -60,7 +60,8 @@ enum{NONE};
 
 FixNVESpin::FixNVESpin(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg),
-  pair(nullptr), spin_pairs(nullptr),
+  pair(nullptr), spin_pairs(nullptr), locklangevinspin(nullptr), 
+  locksetforcespin(nullptr), lockprecessionspin(nullptr),
   rsec(nullptr), stack_head(nullptr), stack_foot(nullptr),
   backward_stacks(nullptr), forward_stacks(nullptr)
 {
@@ -76,7 +77,7 @@ FixNVESpin::FixNVESpin(LAMMPS *lmp, int narg, char **arg) :
   npairspin = 0;
   
   // test nprec
-  nprecspin = 0;
+  nprecspin = nlangspin = nsetspin = 0;
 
   // checking if map array or hash is defined
 
@@ -128,7 +129,6 @@ FixNVESpin::FixNVESpin(LAMMPS *lmp, int narg, char **arg) :
   maglangevin_flag = 0;
   tdamp_flag = temp_flag = 0;
   setforce_spin_flag = 0;
-
 }
 
 /* ---------------------------------------------------------------------- */
@@ -141,6 +141,8 @@ FixNVESpin::~FixNVESpin()
   memory->destroy(forward_stacks);
   memory->destroy(backward_stacks);
   delete [] spin_pairs;
+  delete [] locklangevinspin;
+  delete [] lockprecessionspin;
 }
 
 /* ---------------------------------------------------------------------- */
@@ -261,20 +263,52 @@ void FixNVESpin::init()
   if (count2 != nprecspin)
     error->all(FLERR,"Incorrect number of fix precession/spin");
 
-  // ptrs on the FixLangevinSpin class
+  // set ptrs for fix langevin/spin styles
+  
+  // loop 1: obtain # of fix langevin/spin styles
   
   for (iforce = 0; iforce < modify->nfix; iforce++) {
     if (strstr(modify->fix[iforce]->style,"langevin/spin")) {
-      maglangevin_flag = 1;
+      nlangspin++;
-      locklangevinspin = (FixLangevinSpin *) modify->fix[iforce];
     }
   }
   
-  if (maglangevin_flag) {
+  // init length of vector of ptrs to precession/spin styles
-   if (locklangevinspin->tdamp_flag == 1) tdamp_flag = 1;
+
-   if (locklangevinspin->temp_flag == 1) temp_flag = 1;
+  if (nlangspin > 0) {
+    locklangevinspin = new FixLangevinSpin*[nprecspin];
   }
   
+  // loop 2: fill vector with ptrs to precession/spin styles
+
+  count2 = 0;
+  if (nlangspin > 0) {
+    for (iforce = 0; iforce < modify->nfix; iforce++) {
+      if (strstr(modify->fix[iforce]->style,"langevin/spin")) {
+        maglangevin_flag = 1;
+        locklangevinspin[count2] = (FixLangevinSpin *) modify->fix[iforce];
+        count2++;
+      }
+    }
+  }
+  
+  if (count2 != nlangspin)
+    error->all(FLERR,"Incorrect number of fix precession/spin");
+  
+  // // ptrs on the FixLangevinSpin class
+
+  // for (iforce = 0; iforce < modify->nfix; iforce++) {
+  //   if (strstr(modify->fix[iforce]->style,"langevin/spin")) {
+  //     maglangevin_flag = 1;
+  //     locklangevinspin = (FixLangevinSpin *) modify->fix[iforce];
+  //   }
+  // }
+
+  // if (maglangevin_flag) {
+  //  if (locklangevinspin->tdamp_flag == 1) tdamp_flag = 1;
+  //  if (locklangevinspin->temp_flag == 1) temp_flag = 1;
+  // }
+
   // ptrs FixSetForceSpin classes
 
   for (iforce = 0; iforce < modify->nfix; iforce++) {
@@ -515,12 +549,15 @@ void FixNVESpin::ComputeInteractionsSpin(int i)
   // update langevin damping and random force
 
   if (maglangevin_flag) {               // mag. langevin
-    if (tdamp_flag) {                   // transverse damping
+    for (int k = 0; k < nlangspin; k++) {
-      locklangevinspin->add_tdamping(spi,fmi);
+      locklangevinspin[k]->compute_single_langevin(i,spi,fmi);
-    }
-    if (temp_flag) {                    // spin temperature
-      locklangevinspin->add_temperature(fmi);
     }
+    // if (tdamp_flag) {                   // transverse damping
+    //   locklangevinspin->add_tdamping(spi,fmi);
+    // }
+    // if (temp_flag) {                    // spin temperature
+    //   locklangevinspin->add_temperature(fmi);
+    // }
   }
 
   // update setforce of magnetic interactions

src/SPIN/fix_nve_spin.h

@@ -61,11 +61,15 @@ friend class PairSpin;
   int tdamp_flag, temp_flag;
   int setforce_spin_flag;
 
-  // pointers to magnetic fixes
+  // pointers to fix langevin/spin styles
 
-  // class FixPrecessionSpin *lockprecessionspin;
+  int nlangspin;
-  class FixLangevinSpin *locklangevinspin;
+  class FixLangevinSpin **locklangevinspin;
-  class FixSetForceSpin *locksetforcespin;
+  
+  // pointers to fix setforce/spin styles
+  
+  int nsetspin;
+  class FixSetForceSpin *locksetforcespin; // to be done
   
   // pointers to fix precession/spin styles
 

src/SPIN/fix_precession_spin.cpp

@@ -433,7 +433,6 @@ void FixPrecessionSpin::compute_anisotropy(double spi[3], double fmi[3])
   fmi[0] += scalar*Kax;
   fmi[1] += scalar*Kay;
   fmi[2] += scalar*Kaz;
-  // printf("fm pres1: %g %g %g \n",fmi[0],fmi[1],fmi[2]);
 }
 
 /* ---------------------------------------------------------------------- */