thank you very much for your fast reply. The script worked like a charm
after I've recompiled LAMMPS with the ewald/n method and used this method
instead of P3M. The results it returned are actually pretty good aswell.
The strain we've applied previously is quite big indeed. However, I did want
to make sure that we do not run into any instabilities during the actual
simulation where we deform particles quite heavily.
Well, let me thank you again. Your hint relly helped a lot and is definately
a time safer compared to our previous method.
Have a nice weekend!
----- Chuck's Reply -----
It will take you only a short time to modify the in.elastic scripts in the
LAMMPS examples folder to compute the entire elastic constant matrix of ZnS.
You will need to build the lattice in init.mod and change the potential type
in potential.mod but it will be worth it. In there you will see that the
deformation applied to the box is very small. 1% is a huge deformation for
many materials. The elastic constant script applies orders of magnitude
less deformation than what you have applied. You should be thinking of only
applying about 0.01% or less. A strain of about 10^-6, for example.
From that information you can quickly compute the bulk modulus but you will
also have the entire elastic matrix.