[lammps-users] Shock modelling of polymer

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1

Dear Lammps Users,
I am using the 2020 version of lammps. I am modelling the polyethylene for shock loading using wall/piston comman on the z lower dimension. I am facing some problem while applying the shock load on the simulation cell.

  1. During the simulation, temperature of the simulation cell overshoot rapidly to a large value and the simulation box dimension increases continuously.
  2. I am applying the rigid piston on the lower edge of the z dimension and the upper edge of the z dimension getting increased

INPUT SCRIPT

variable fname index data.pe
variable simname index polyethyene

##########Initializing simulation#################
units metal
boundary p p p
atom_style atomic
atom_modify map array

##Defining Atom Coordinates#####
log log.${simname}.txt
read_data data.pe

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

pair_style airebo 3.0
pair_coeff * * CH.airebo H C
neighbor 2 bin
neigh_modify every 2 delay 0 check no

2

This is normal. If a shockwave is established with this method, your box will be moving at the speed of the particle velocity. If no shockwaves, it is moving at the impact velocity.