On the relative stability of orthorhombic and hcp phases of beryllium at high pressures

High-pressure electronic properties of Be have been investigated theoretica lly by means of ab initio electronic structure calculations. The calculatio ns have been carried out by the semirelativistic full-potential, linear muf fin-tin orbital (FPLMTO) method, within the local density approximation. Th e crystal structure stability among the hcp, bcc and orthorhombic (distorte d hcp) phases has been studied as a function of compression. The bcc struct ure is found to be energetically stable at pressures above 180 GPa. From th e results of our calculations, the orthorhombic phase cannot occur as an in termediate phase between the ambient pressure hcp phase and the high-pressu re bcc structure. Our work thus suggests the need for more accurate high-pr essure x-ray data.