Regarding shock absorption

Dear All,
I want to absorb shock (acoustic wave) in my system at the boundary (or wall).
Can LAMMPS do this?
Thanks in advance.

Regards

Dear All,
I want to absorb shock (acoustic wave) in my system at the boundary (or
wall).
Can LAMMPS do this?

​rather than asking for something specific, you should consider what
actually constitutes the absorbing: the kinetic energy of the incoming wave
is dissipated. now consider how this effect can be most easily reproduced
in a simulation: you could use a dissipative thermostat with a suitably
short time constant​, e.g. fix langevin, fix csld, fix gle, fix gld etc.
you cannot just remove the kinetic energy instantly, as that would be like
kicking and cooling down your system (unless you want that) and you would
cause a (partial) reflection. to make it work at a boundary/wall, you would
need to apply this thermostat to a specific region only.

if you want to do something more complex, e.g. a position dependent
friction force in only one specific direction, you could use fix addforce
with an atom style variable that computes the added force based on position
and velocity

axel.