# What information about a crystalline solid material goes into calculating phase diagrams in Thermo-Calc, and how?

Gibbs free energy, $$G$$, for a crystalline solid material could be described as: $$$$G\: =\: H_{T=0}\: +\: H_{T>0}\: +\: \text{ZPE}\: -\: T\cdot S,$$$$ Where $$H$$ is enthalpy, ZPE is the zero-point energy and S is entropy (all kinds).

Solids (condensed matter might be a better term) are highly incompressible, so their internal energy computed with either empirical potentials or otherwise can be considered equal to their enthalpy. That takes care of the $$H_{T=0}$$ term. What about the rest? Can each of them be included in a Thermocalc phase transition study?

I haven't explored Thermocalc enough (blame it on VASP!). As far as I know, we make Gibbs free energy equations for a material at various temperature ranges and dump those in a .tdb (database) file. If these other terms are accounted for, please help me understand how, code and theory-wise.

• It is unusual for a question on our site to have only one vote. Does anyone want to explain why I was the only one that voted?! – Nike Dattani Dec 7 '20 at 3:19