hcp to fcc transition in silicon at 78 GPa and studies to 100 GPa

The pressure-induced phase sequence of silicon has been studied to 100 GPa by energy-dispersive x-ray diffraction techniques. A new phase transition from hexagonal close-packed to face-centered cubic was observed at a volume compression of V/V₀=0.481±{}0.005 and 78±{}3 GPa, in excellent agreement with first-principles calculations of the phase stability of silicon at high pressures. This represents the lowest atomic number material for which a structural determination has been made to 100 GPa.