- improved design of test_problem

- cleaned up langevin/spin
- started doc for stt and hexaniso

doc/src/fix_precession_spin.rst

@@ -12,7 +12,7 @@ Syntax
 
 * ID, group are documented in :doc:`fix <fix>` command
 * precession/spin = style name of this fix command
-* style = *zeeman* or *anisotropy* or *cubic*
+* style = *zeeman* or *anisotropy* or *cubic* or *stt* or *hexaniso*
 
   .. parsed-literal::
 
@@ -22,12 +22,15 @@ Syntax
        *anisotropy* args = K x y z
          K = intensity of the magnetic anisotropy (in eV)
          x y z = vector direction of the anisotropy
-
-  .. parsed-literal::
-
        *cubic* args = K1 K2c n1x n1y n1x n2x n2y n2z n3x n3y n3z
          K1 and K2c = intensity of the magnetic anisotropy (in eV)
          n1x to n3z = three direction vectors of the cubic anisotropy
+       *stt* args = J x y z
+         H = intensity of the spin-transfer torque field (in Tesla)
+         x y z = vector direction of the field
+       *hexaniso* args = K6 x y z
+         H = intensity of the spin-transfer torque field (in Tesla)
+         x y z = vector direction of the field
 
 Examples
 """"""""

examples/SPIN/test_problems/README

@@ -45,3 +45,14 @@ directory.
   results (computed by the python script).
   Note: This example is a reworked version of a test problem 
   provided by Martin Kroger (ETHZ).  
+
+- validation_nve:
+  simulates a small assembly of magnetic atoms (54). The atoms are 
+  coupled by an exchange interaction and a mechanical potential 
+  (EAM here). 
+  This example represents an NVE run: the total energy of the 
+  system is preserved, whereas the spin and lattice energy 
+  reservoirs are exchanging energy.
+  Run as: ./run-test-nve.sh
+  Output: res_lammps.dat contains the data. The results are displayed
+  by nve_spin_lattice.pdf. 

examples/SPIN/test_problems/run_all.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# test 1: damping and exchange 
+cd validation_damped_exchange/
+./run-test-exchange.sh
+rm dump.data res_lammps.dat res_llg.dat
+cd ..
+
+# test 2: damping and Zeeman
+cd validation_damped_precession/
+./run-test-prec.sh
+rm res_lammps.dat res_llg.dat
+cd ..
+
+# test 3: langevin, damping and Zeeman
+cd validation_langevin_precession/
+./run-test-prec.sh
+rm average_spin test-prec-spin.in res_lammps.dat res_langevin.dat
+cd ..
+
+# test 4: NVE run, test Etot preservation
+cd validation_nve/
+./run-test-nve.sh
+rm nve_spin_lattice.pdf res_lammps.dat
+cd ..

src/SPIN/fix_langevin_spin.cpp

@@ -45,7 +45,7 @@ using namespace MathConst;
 /* ---------------------------------------------------------------------- */
 
 FixLangevinSpin::FixLangevinSpin(LAMMPS *lmp, int narg, char **arg) :
-  Fix(lmp, narg, arg), id_temp(nullptr), random(nullptr)
+  Fix(lmp, narg, arg), random(nullptr)
 {
   if (narg != 6) error->all(FLERR,"Illegal langevin/spin command");
 
@@ -53,14 +53,6 @@ FixLangevinSpin::FixLangevinSpin(LAMMPS *lmp, int narg, char **arg) :
   alpha_t = utils::numeric(FLERR,arg[4],false,lmp);
   seed = utils::inumeric(FLERR,arg[5],false,lmp);
 
-  dynamic_group_allow = 1;
-  scalar_flag = 1;
-  global_freq = 1;
-  extscalar = 1;
-  ecouple_flag = 1;
-  nevery = 1;
-  tallyflag = 1;
-
   if (alpha_t < 0.0) {
     error->all(FLERR,"Illegal langevin/spin command");
   } else if (alpha_t == 0.0) {
@@ -117,10 +109,8 @@ void FixLangevinSpin::init()
 
   double hbar = force->hplanck/MY_2PI;  // eV/(rad.THz)
   double kb = force->boltz;             // eV/K
-  // D = (MY_2PI*alpha_t*gil_factor*kb*temp);
 
   D = (alpha_t*gil_factor*kb*temp);
-  // D = (12.0/MY_2PI)*(MY_2PI*alpha_t*gil_factor*kb*temp);
   D /= (hbar*dts);
   sigma = sqrt(2.0*D);
 }
@@ -163,7 +153,6 @@ void FixLangevinSpin::add_temperature(int i, double spi[3], double fmi[3])
   double rz = sigma*random->gaussian();
   double hbar = force->hplanck/MY_2PI;
 
-  energyS += 0.25*hbar*(rx*spi[0]+ry*spi[1]+rz*spi[2])*update->dt;
   // adding the random field
 
   fmi[0] += rx;
@@ -187,16 +176,3 @@ void FixLangevinSpin::compute_single_langevin(int i, double spi[3], double fmi[3
     if (temp_flag) add_temperature(i,spi,fmi);
   }
 }
-
-/* ---------------------------------------------------------------------- */
-
-double FixLangevinSpin::compute_scalar()
-{
-  if (!tallyflag) return 0.0;
-
-  double energy_all;
-  MPI_Allreduce(&energyS,&energy_all,1,MPI_DOUBLE,MPI_SUM,world);
-  return -energy_all;
-}
-
-/* ---------------------------------------------------------------------- */

src/SPIN/fix_langevin_spin.h

@@ -36,7 +36,6 @@ class FixLangevinSpin : public Fix {
   void add_tdamping(double *, double *);                 // add transverse damping
   void add_temperature(int, double *, double *); 
   void compute_single_langevin(int, double *, double *);
-  virtual double compute_scalar();
 
  protected:
   double alpha_t;               // transverse mag. damping
@@ -44,11 +43,6 @@ class FixLangevinSpin : public Fix {
   double temp;                  // spin bath temperature
   double D,sigma;               // bath intensity var.
   double gil_factor;            // gilbert's prefactor
-  double energyS;
-  int nlocal_max;
-  int tallyflag;
-  char *id_temp;
-  class Compute *temperature;
 
   int nlevels_respa;
   class RanMars *random;