Elastic Coefficients for Poly atomic species

Dear all,

I’m new to lammps and I’m now working on a project to find the elastic coefficients using hydrostatic strain.

I found the example program ‘ELASTIC’ in lammps for Silicon.

I modified the program and potential as mentioned in it for my poly-atomic crystal.

But the values are not matching and it keeps deviating when the ${up} variable is changed.

Is there anything else other than pair potentials and structure file I have to modify for polyatomic species???

I’m getting wrong values for all poly-species I’ve tried.

Could someone please shed light on this. I’m just a beginner in lammps.

Thanks in advance.

Please do not post to both the mailing list and the forum. Choose one to post to first and only if you don’t receive a suitable response within a few days, you should post to the other.

Since you are new to LAMMPS you should not start with “advanced” simulation topics right away.
But rather first gain some experience. You will need that anyway and some suitable tutoring/training as the LAMMPS developers may be able to help you with the technical aspects (i.e. how to use the correct syntax and how to address bugs and limitations), but for anything related to the “science”, it is not something that can be obtained easily from a mailing list. There are some comments about what to watch out for in the input script files, but it is ultimately your responsibility to check and make certain that your calculations are meaningful and the settings, parameters, system sizes are chosen as such that you get reliable and well converged results. This is usually best done while being tutored by somebody with practical experience.