My Community

I have a couple of phases that I would like to compare the relative stability of with respect to pressure. I plan to do so via the enthalpy. I have calculated the change in enthalpy H as a function of applied pressure for each phase without problem using Vasp. I have also calculated the thermal properties using phonopy-qha (quasi harmonic approximation) to solve for Cp at equilibrium. I am planning to add the phonon related enthalpic contributions by adding the int(Cp dT) to calculate delta H. I can calculate from a Maxwell relation that (dCp/dP)T is -T(d^2 V/dT^2)P, but while I have calculated the expansion coefficient using phonopy-qha, it is not as trivial to calculate the second derivative of the coefficient of expansion with respect to temperature. Looking at the term, it seems likely to be small. I am curious if anyone has experience with this and would it be fair to assume that Cp is pressure independent to 10 kB or so? Thanks for any advice in advance.

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

Best wishes,

VASP