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)