First-principles pseudopotential study of the structural phases of silicon

A first-principles pseudopotential study of 11 phases of silicon is reported: diamond (cd), body-centered cubic (bcc), face-centered cubic (fcc), body-centered tetragonal (bct), simple hexagonal (sh), hexagonal-close-packed (hcp), double-hexagonal-close-packed (dhcp), simple cubic (sc), β-tin, a body-centered cubic structure with eight atoms per unit cell (bc8), and a simple tetragonal structure with 12 atoms per unit cell (st12). For each structure and for each volume considered we have minimized the energy with respect to all structural degrees of freedom. We have used large basis sets and very careful integrations over the Brillouin zone to resolve the small energy differences between structures, and our pseudopotentials incorporate nonlinear core exchange-correlation corrections, leading to more accurate results than those of previous calculations. We find good agreement with experiments and with some previous calculations but a few discrepancies remain and we gain some insights into the high-pressure phase diagram of silicon.