PSEUDOPOTENTIAL STUDY OF THE STRUCTURAL-PROPERTIES OF BULK LI

The phase stability of the hcp, fcc, and bcc structures of Li is studi ed using the pseudopotential density-functional total-energy calculati on scheme. The order of the crystal energy at zero pressure is E(hcp) < E(fcc) < E(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 hc p-to-fcc transition occurs at a pressure of about 15 kbar. Unlike a pr evious pseudopotential calculation, which predicted a fcc-to-bcc trans ition, but no hcp-to-fcc transition, the present result on the transit ions is in good agreement with existing all-electron calculations.