Firstprinciples derivation and properties of densityfunctional averageatom models
Abstract
Finitetemperature KohnSham density functional theory (KSDFT) is a widelyused method in warm dense matter (WDM) simulations and diagnostics. Unfortunately, full KSDFTmolecular dynamics models scale unfavourably with temperature and there remains uncertainty regarding the performance of existing approximate exchangecorrelation (XC) functionals under WDM conditions. Of particular concern is the expected explicit dependence of the XC functional on temperature, which is absent from most approximations. Averageatom (AA) models, which significantly reduce the computational cost of KSDFT calculations, have therefore become an integral part of WDM modeling. In this paper, we present a derivation of a firstprinciples AA model from the fullyinteracting manybody Hamiltonian, carefully analyzing the assumptions made and terms neglected in this reduction. We explore the impact of different choices within this model—such as boundary conditions and XC functionals—on common properties in WDM, for example equationofstate data, ionization degree and the behavior of the frontier energy levels. Furthermore, drawing upon insights from groundstate KSDFT, we discuss the likely sources of error in KSAA models and possible strategies for mitigating such errors.
 Publication:

Physical Review Research
 Pub Date:
 April 2022
 DOI:
 10.1103/PhysRevResearch.4.023055
 arXiv:
 arXiv:2103.09928
 Bibcode:
 2022PhRvR...4b3055C
 Keywords:

 Condensed Matter  Materials Science;
 Physics  Chemical Physics;
 Physics  Plasma Physics
 EPrint:
 To be published in Physical Review Research. 29 pages, 15 figures. Derivation of Hamiltonian clarified since v3 and added appendix B on computation of free energy