Alternative approaches for calculations of exchange and correlation contributions to thermodynamic properties

The cumulant expansion of the one-electron Green’s function has been found to be an improved method for calculations of excited states and spectra for a wide variety of systems [1]. Additionally, an extension of the cumulant Green’s function approach to finite temperatures has yielded total energies and exchange correlation potentials in good agreement with quantum Monte-Carlo results [2]. Here we present an investigation of alternative thermodynamic pathways for properties such as the free energy, entropy, and heat capacity of the homogeneous electron gas. In addition we discuss approximate methods based on quasiparticle properties alone. These approximate methods improve the efficiency of the approach, and could be applied to real systems for which calculations of GW quasiparticle effects are computationally reasonable.
[1] J.S. Zhou et al., J Chem Phys. 143, 184109 (2015)
[2] J.J. Kas, J.J. Rehr, Phys. Rev. Lett. 119, 176403 (2017)