Ground-state properties and structural phase transformation of beryllium oxide

The electronic structure, the charge density and the total energy of BeO in the rocksalt (B1), caesium chloride (B2), zincblende (B3), wurtzite (B4), nickel arsenide (f) and iron silicide (B28) structures are studied using first-principles self-consistent local-density calculations in a large plane wave basis employing soft non-local pseudopotentials. Experimentally no transition was observed up to a pressure of 55 GPa. The wurtzite structure is the calculated ground state with a = 2.639 A, c = 4.299 A, c/a = 1.629 and an internal parameter u = 0.377. The experimental values are respectively 2.699 A, 4.373 A, 1.62 and 0.378. The zincblende structure is energetically very close to the wurtzite structure. The difference at the minimal energy between these two structures is only 5.6 meV. At a pressure of 137 GPa we observe a transition to the sixfold-coordinated rocksalt structure. From that structure on, no other transition is found to any of the calculated structures.