I would like to calculate the above quantities for a given unit cell (or supercell) with arbitrary symmetry. Specifically, I am trying to use a machine-learned interatomic potential (MLIP), and since the MLIP will only give me energies for given atomic configurations, I need to be able to calculate these elastic constants using energies only. I know, for instance, that the bulk modulus can be calculated by changing the lattice parameter and fitting the energy curve to the Birch-Murnaghan equation of state (EOS), but I am not sure what to do for Poisson's ratio.

Any help is greatly appreciated, and if this has already been asked before I would be happy to be redirected to those answers. However, from the searching that I did, I could not find answers pertaining to going from energies to moduli. Thanks in advance!

  • $\begingroup$ +1 and welcome to our new community! You're basically asking four questions though, which is against our one question per post policy. Can you narrow it down to the property that you most urgently need to study, then perhaps ask the other questions in separate posts, depending on whether or not the answers that you get to the first question are not sufficient for the rest of your work? $\endgroup$ Oct 14, 2023 at 0:59
  • $\begingroup$ Can't your MLIP also give you forces? What about stresses? $\endgroup$ Oct 15, 2023 at 1:14
  • $\begingroup$ @PhilHasnip Yes the MLIP can get me forces and stresses $\endgroup$
    – xlr
    Oct 15, 2023 at 18:48
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    $\begingroup$ @NikeDattani Apologies, I have edited the question to only the Poisson's ratio $\endgroup$
    – xlr
    Oct 15, 2023 at 18:49