Hi,
I am trying to run a pka cascade model on a NiFe alloy. More specifically I am trying to run several subsequent cascades (about 500). The idea is to pick a random atom in the box and give it a velocity (1e+3 A/ps) in the y direction. In order to run the subsequent cascade I apply a loop – next (jump SELF) cycle and a read-restart command for initiating the new cascade with the box as it was left in the previous cascade.
The problem is very soon in the cascades (after about 10-50 cascades) the box expands into a very bigger box and the microstructure begins to fall apart leaving nothing but small “droplets” of atoms very far one from each other. I tried several times with different settings but nothing I tried solved the problem.
I attach here an example of input file that may better explain what I was trying to do.
---------- INITIALIZATION ----------------------------------------------------
clear
timer full
units metal
dimension 3
boundary p p p
atom_style atomic
---------- GEOMETRY DEFINITION -----------------------------------------------
variable a loop 500
reset_timestep 0
read_restart NiFe_rst.*
group Fe type 1
group Ni type 2
group Cr type 3
region xlow block 0 0.5 0 30 0 30 #units box
region xhigh block 29.5 30 0 30 0 30 #units box
region ylow block 0 30 0 0.5 0 30 #units box
region yhigh block 0 30 29.5 30 0 30 #units box
region zlow block 0 30 0 30 0 0.5 #units box
region zhigh block 0 30 0 30 29.5 30
group xbot region xlow
group xtop region xhigh
group ybot region ylow
group ytop region yhigh
group zbot region zlow
group ztop region zhigh
group boundary union xbot xtop ybot ytop zbot ztop
--------- FORCE FIELD -------------------------------------------------------
pair_style eam/alloy
pair_coeff * * FeNiCr_Bonny_2013_ptDef.eam.alloy Fe Ni Cr
---------- SETTINGS ----------------------------------------------------------
COMPUTES
compute eng all pe/atom
compute new all temp
---------- DYNAMICS ----------------------------------------------------------
run 0
PRINT-SCREEN
thermo 1000
thermo_style custom step pe lx ly lz press pxx pyy pzz
--------- set temperature ----------------------------------------------------
fix 1 all dt/reset 10 0.0001 0.01 0.05 units box
fix 2 all npt temp 300 300 100 iso 1 1 1
run 100000
unfix 1
--------- run PKA cascade ----------------------------------------------------
reset_timestep 0
fix 3 all dt/reset 10 0.0001 0.01 0.05 units box
variable mypka equal round(random(1,108000,$a*146324)) # the box has 108000 atoms
group PKA id ${mypka}
velocity PKA set 0.0 1e3 0.0 units box
fix 4 boundary nvt temp 300 300 100 # Nosé-Hoover
run 50000
unfix 3
---------- minimize ----------------------------------------------------------
min_style cg
minimize 1e-15 1e-15 15000 15000
reset_timestep 0
dump 1 all custom 1000 dump.relax.1.$a id type xs ys zs c_eng
run 1000
undump 1
---------- OUTPUTS -----------------------------------------------------------
write_restart NiFe_rst.*
run 0
variable my_pe equal pe
print ${my_pe} append PE.fdata
next a
jump SELF