Assessing the suitability of temperature-dependent coefficients in zero-temperature models for the strong interaction limit

Density functional theory, a widely used quantum mechanical method, has been a powerful tool in simulating high-temperature processes such as fusion reactions conducted at the National Ignition Facility. The thermal upside-down adiabatic connection is a formalism that smoothly connects the physical system at a specific density to a fictitious infinitely interacting (strictly correlated) reference system via a scaling factor. This method yields an exact expression for the decorrelation free energy, the missing piece needed to calculate the total free energy of the realistically interacting system. While this technique is well established at zero temperature, further work is needed to apply this method to finite-temperature systems. This work probes the use of zero-temperature methods for calculating decorrelation free energies at finite temperatures. Comparisons to zero-temperature upside-down adiabatic connection curves help identify limitations in the infinitely interacting limit of the current formalism. Further investigation into the strictly correlated reference system in temperature-dependent applications will also be discussed.