[lammps-users] to find CRSS for dislocation motion

Dear steve,

i am trying to repeat the work published by osetsky in “Modelling and simulation in Materials science and engineering,11(2003)427-446”.

1.creation of domain with dislocation has been done.
2.Movement of dialocation at 0 k is also simulated.

But i am unable to get the Criticle resolved shear stress required to move the dislocation at 10K, which is repoted in paper as 25MPa.
i used the following steps in the input file

first the minmization of the domain using minimization commond.
thermal equilibration for 1000 time steps.
applying shear strain of 10^-5 per time step. at the same time dumping the stress values per atom of the upper group of atoms
and dividing by the number of atoms in the group to get avg stresss.(stress/volume)

the above steps are run in loop for 100 times to get 0.1% strain as in the paper.
is it wright?if not plz help me.
The input file using for the simulation is given below

3d metal shear simulation os box size 80*50 with dislocation

units metal
boundary p s p
atom_style atomic
lattice bcc 2.855324
read_data FORT.12
pair_style eam/fs
pair_coeff * * Fe_mm.eam.FS Fe
neighbor 2 bin
neigh_modify delay 5

region lower block INF INF INF 0 INF INF
region upper block INF INF 70 INF INF INF
region plot block INF INF 30 40 INF INF
group lower region lower
group upper region upper
group plot region plot
group bound union lower upper
group plot1 union plot bound
group m subtract all bound

temp controllers

compute new3d m temp
compute str upper stress/atom
compute sum upper reduce sum c_str[4]
compute 1 plot pe/atom
compute 2 plot centro/atom

fix 1 m nve
timestep 0.001

label loopa
variable a loop 200
print “A = $a”
fix 20 bound setforce 0 0 0
minimize 1.0e-10 1.0e-10 20000 20000
min_style cg
velocity m create 10.0 100000 temp new3d
fix 10 m temp/rescale 1 10.0 10.0 2.0 0.5
run 1000
velocity upper set 2 0 0
dump 21 bound custom 1 dump.pecentro.$a id x y z c_1
dump 22 upper custom 1 dump.upperstrs.$a id c_str[4] fx
run 1

undump 21
undump 22

next a
jump in.shear2 loopa

with regards

I don't know. I assume you've checked
that the system is indeed deforming as you
hope, via visualization or other diagnostics. Are
there other quantities besides dislocation movement
you can compare between your runs and the paper?
Are you using the same potential as in the paper, since
that can make a difference?