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 α-BeH2 at the equilibrium volume are in very good agreement with experiments. At higher pressures α-BeH2 successively undergoes four structural transitions: (i) α- to β-BeH2 at 7.07 GPa; (ii) β- to γ-BeH2 at 51.41 GPa; (iii) γ- to δ-BeH2 at 86.56 GPa; and (iv) δ- to e-BeH2 at 97.55 GPa [an effective two-phase (γ and δ) 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.