GAUSSIAN-BASIS LDA AND GGA CALCULATIONS FOR ALKALI-METAL EQUATIONS OFSTATE

Recently there has been renewed interest in implementations of density -functional theory for solids using various types of localized basis s ets, including atom-centered Gaussian-type functions. While such metho ds are clearly well adapted to most insulating and semiconducting syst ems, one might expect them to give a less-than-optimal description of metals relative to plane-wave-type methods. Nevertheless, several succ essful applications of local-basis methods to metals have recently bee n reported. Here, we report an application of our Gaussian linear comb ination of atomic orbitals (LCAO) code to some extremely free-electron -like metals, namely, the alkali metals Li, Na, and K. In agreement wi th other calculations (both local and plane wave) we find that the loc al-density approximation (LDA) lattice constants are relatively poor ( similar to-3% from experiment for the alkali metals versus +/-1% for m any other solids) and that the LDA bulk moduli are similar to 30% too high. We find that the Perdew-Burke-Enzerhof (PBE) version of the gene ralized-gradient approximation (GGA) corrects most of this error, in a greement with earlier calculations using similar GGA functionals. The Becke-Lee-Yang-Parr GGA functional gives similar results for the alkal i-metal equations of state but is found to overcorrect the errors of t he LDA for the cohesive energies, for which the PBE functional is in b etter agreement with experiment. Our results indicate that the Gaussia n-LCAO method should be able to give accurate results for nearly any c rystalline solid, since it succeeds even where it would be expected to have the most difficulty. [S0163-1829(98)07919-3].