Using the generalized thermal adiabatic connection to analyze and build exchange-correlation free energy approximations

Warm dense matter is a highly energetic phase found within planetary cores that exhibits properties of both plasmas and solids. Thermal density functional theory is commonly used to simulate this challenging phase, driving development of temperature-dependent approximations to the exchange-correlation free energy. The generalized thermal adiabatic connection (GTAC) introduces a fictitious temperature parameter that allows temperature to vary along the AC pathway, which is useful for generating approximations to entropic and kinetic free energy components. Previously demonstrated for LDA-level parameterizations of the exchange-correlation (XC) free energy, this approach will next be used to extract the XC entropy from a thermal GGA and applied to approximate AC curves at zero temperature.