Thermodynamic Properties of the Electron Gas from the Cumulant Green’s Function Approach

We present results for thermodynamic properties of the spin polarized electron gas based on the one electron cumulant Green's function approach and the Galitskii-Migdal-Koltun sum-rule. This approach was recently extended to finite temperature calculations for the unpolarized electron gas [1], and gives good agreement in comparison with results from quantum Monte-Carlo (QMC) calculations of exchange-correlation energies over a wide range of temperatures and densities. Excited state properties not readily available from QMC were also calculated. Here we describe extensions to include spin-polarization, the exchange correlation free-energy and entropy, together with comparisons to QMC data and DFT fits. In addition, we extend the static COHSEX approximation of the self-energy to finite temperature, and discuss the quality of this approximation along with possible improvements [2].
[1] J. J. Kas and J. J. Rehr, Phys. Rev. Lett. 119, 176403 (2017)
[2] Wei Kang and Mark S. Hybertsen, Phys. Rev. B 82, 195108 (2010)