Fermi surface of alkali metals using the full-potential linear muffin-tin orbital method and the generalized gradient approximation.

Abstract

The Fermi surface (FS) of the alkali metals (Li, Na, K, Rb, and Cs) has been studied using a full-potential linear muffin-tin orbital (FPLMTO) method together with both the local-density approximation (LDA) and the generalized gradient approximation of Perdew and Wang (PW91). We demonstrate that FPLMTO calculations based on the LDA improve the FS of K, Rb, and Cs compared to LMTO calculations within the atomic-sphere approximation (ASA). Most importantly, our FPLMTO-LDA calculations reproduce all essential features of the FS of Cs, whereas the previous LMTO-ASA LDA calculations erroneously resulted in a FS that is open at the N point. The gradient-corrected FPLMTO calculations further improve the FS for K, Rb, and Cs and give results in good agreement with experiment. For Li and Na the FPLMTO calculations slightly worsen the FS, both when using the LDA and PW91.