"Must shrink-wrap piston boundary"

Hi,

Your using velocity shock_part NULL NULL 0.02 units box # (Apply velocity (Up).
So your already compressing the sample: System is launched towards a static mirror that reflects every particle . In other words, the sample is slammed up against a specularly reflecting wall with velocity Up. As a result a shockwave is propagated in the other sense at velocity Us‐Up.

A Salute
Oscar G.

Thanks Oscar, for your prompt response. so I have defined my shock commands and when I run the simulations, I get the following error

ERROR: Bond/angle/dihedral extent > half of periodic box length (domain.cpp:580). I understand that this is more of a structural problem than a lammps problem, however I have double checked my structure and verified the thermal-physical properties to be comparable with experiments. This only happens when I remove the periodicity in the Z direction. Any suggestion/lead on how to fix this error?

No idea …

A Salute
Oscar G.

It means the following:

delta = 1/2 the smallest periodic box length
You have a bond that is longer than delta.
Or if you have angles/dihedrals, then 2*bond-length
or 3*bond-length is longer than delta.

If this is the case, LAMMPS has no way to know
which perioidic image of the atoms in that bond/angle/dihedral
to use when computing the bond.

Is that the case for your model? I don't know why you
would only get the error when you make z non-periodic.
That doesn't make sense.

Steve