[lammps-users] Generating Shock by Shrinking Periodic Boundaries


I am using LAMMPS Version marked 12 Dec 2018. I have been trying to conduct shock simulations by shrinking the periodic boundary along the longest dimension of a cuboid shaped domain (as used in this paper: https://doi.org/10.1063/1.1554489). The paper states:

A planar shock wave was initiated at time zero by shrinking the periodic computational cell length Lx according to Lx(t)=Lx(0)-2upt ,while keeping the lengths Ly and Lz fixed.

This approach is expected to create two shock fronts that approach the center of the domain from the two periodic boundaries. My input script is as follows, where I am using ‘fix deform’ to shrink the periodic boundary at a certain velocity. However, no shock waves are created and the domain undergoes homogeneous shrinkage along z-axis at a constant rate. I understand that I am missing something fundamental here, since some kind of inhomogeneous deformation is needed to generate a shock front. Any help would be appreciated.

units real

boundary p p p

atom_style charge

read_restart restart.b4c.108000

pair_style reax/c lmp_control

pair_coeff * * ffield.reax C B B B B B B B B B B B C B C

neigh_modify every 5 delay 0 check yes

timestep 0.1

thermo 50

restart 4000 restart.b4c

compute p all stress/atom NULL

dump data all custom 200 dump.data id type mass x y z vx vy vz c_p[*]

fix 1 all qeq/reax 1 0.0 10.0 1e-6 reax/c

fix 2 all nve

fix 3 all deform 1 z vel -0.07

run 10000


Amith Adoor

this discussion has moved to the new forum. https://matsci.org/t/generating-shock-by-shrinking-periodic-boundaries/36176/4