- slight modifs of the damped exchange example

examples/SPIN/test_problems/validation_damped_exchange/llg_exchange.py

@@ -6,9 +6,17 @@ 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 
+J2 = 0.0    # adim
+J3 = 1.0    # in Ang.
+
+# initial spins
 S1 = np.array([1.0, 0.0, 0.0])
 S2 = np.array([0.0, 1.0, 0.0])
+
 alpha=0.01              # damping coefficient
 pi=math.pi
 
@@ -30,6 +38,14 @@ def rotation_matrix(axis, theta):
       [2 * (bc - ad), aa + cc - bb - dd, 2 * (cd + ab)],
       [2 * (bd + ac), 2 * (cd - ab), aa + dd - bb - cc]])
 
+#Definition of the Bethe-Slater function
+def func_BS(x,a,b,c):
+    return 4*a*((x/c)**2)*(1-b*(x/c)**2)*np.exp(-(x/c)**2)
+
+#Definition of the derivative of the Bethe-Slater function
+def func_dBS(x,a,b,c):
+    return 4*a*((x/c)**2)*(1-b*(x/c)**2)*np.exp(-(x/c)**2)
+
 # calculating precession field of spin Sr
 def calc_rot_vector(Sr,Sf):
   rot = (J0/hbar)*(Sf-alpha*np.cross(Sf,Sr))/(1.0+alpha**2)

examples/SPIN/test_problems/validation_damped_exchange/test-spin-precession.in

@@ -21,7 +21,7 @@ pair_coeff	* * exchange 3.1 11.254 0.0 1.0
 variable        Temperature equal 0.0 
 variable        RUN equal 30000
 
-fix             1 all nve/spin lattice no
+fix             1 all nve/spin lattice frozen
 fix             2 all langevin/spin ${Temperature} 0.01 12345
 
 compute		out_mag    all spin
@@ -36,6 +36,9 @@ variable	emag      equal c_out_mag[5]
 thermo_style    custom step time v_magx v_magy v_magz v_emag pe etotal
 thermo          10
 
+compute 	outsp all property/atom spx spy spz sp fmx fmy fmz
+dump 		1 all custom 10 dump.data type x y z c_outsp[1] c_outsp[2] c_outsp[3] fx fy fz
+
 timestep	0.0001
 
 run             ${RUN}