Structural stability of BeH2 at high pressures

The electronic structure and structural stability of BeH2 are studied using first-principles density-functional calculation. The calculated structural parameters for alpha-BeH2 at the equilibrium volume are in very good agreement with experiments. At higher pressures alpha-BeH2 successively undergoes four structural transitions: (i) alpha- to beta-BeH2 at 7.07 GPa; (ii) beta- to gamma-BeH2 at 51.41 GPa; (iii) gamma- to delta-BeH2 at 86.56 GPa; and (iv) delta- to epsilon-BeH2 at 97.55 GPa [an effective two-phase (gamma and delta) region is found at 73.71-86.56 GPa]. Density of states studies reveal that BeH2 remains insulating up to 100 GPa whereupon anomalous changes are seen in the band-gap region with increasing pressure. (C) 2004 American Institute of Physics.