Dear Lammps Users,

Currently I am working on modelling the shock wave for polymer material. I am using the LAMMPS 2017 version. I am modelling the polyethylene for the shock loading.

I am facing some problem those are as follows;

- While applying the wall/piston command on the z lower dimension, the simulation box is moving along the shock direction and the box dimension increases constantly in the z direction.

herewith i have attached the input script. kindly help me to find the problem in the manuscript.

# VARIABLES

variable simname index polyethyene

##########Initializing simulation#################

units real

boundary p p p

atom_style charge

##Defining Atom Coordinates#####

#log log.${simname}.txt

read_data data.pe

## Defining potential####################

pair_style reax/c lmp_control

pair_coeff * * ffield.reax.BN H C

fix spcl all qeq/reax 20 0.0 10.0 1e-6 reax/c #param.qeq

neighbor 2 bin

neigh_modify every 2 delay 0 check no

write_dump all custom EQ_*.dump id type mass x y z q

## Setting (calculating extra properties)

compute mytemp all temp

compute peratom all pe/atom

compute pe all reduce ave c_peratom

compute ke all ke/atom

compute ke1 all reduce ave c_ke

compute strs all stress/atom NULL virial

compute pr all reduce sum c_strs[1] c_strs[2] c_strs[3]

min_style cg

minimize 1e-15 1e-15 10000 10000

velocity all create 300.0 1231141 dist gaussian rot yes