Pseudopotential study of the structural properties of bulk Li

Abstract

The phase stability of the hcp, fcc, and bcc structures of Li is studied using the pseudopotential density-functional total-energy calculation scheme. The order of the crystal energy at zero pressure is ${\mathit{E}}_{\mathrm{hcp}}$${\mathit{E}}_{\mathrm{fcc}}$${\mathit{E}}_{\mathrm{bcc}}$. The two closed-packed structures (fcc and hcp) are fairly stable compared to the bcc structure for all volumes considered, i.e., there is no pressure-induced bcc transition from either hcp or fcc. The energy difference between hcp and fcc is very small and a hcp-to-fcc transition occurs at a pressure of about 15 kbar. Unlike a previous pseudopotential calculation, which predicted a fcc-to-bcc transition, but no hcp-to-fcc transition, the present result on the transitions is in good agreement with existing all-electron calculations.