Dear prof. Gale, sorry to bother you.

I was searching on how to calculate the free energies with GULP and I found out this tutorial: https://www.epj-conferences.org/articles/epjconf/pdf/2011/04/epjconf_ft2m2010_03005.pdf

I tried the two options (a) *grad conp prop phon* or b)*opti free zsisa*) you mentioned there, but I am using the pGFN-FF model.

Consequently, I could not run b) calculation, as the *free* method is not implemented for this model. For a), the calculation runs only if I don’t use the *shrink* keyword, which I understand it is needed so we can integrate across the Brillouin zone to obtain a converged free energy difference.

I am interested on calculating these free

energy differences for different phases of a framework. Is there any other way I can properly calculate the free energy using pGFN-FF in GULP?