Structural Transition from Ordered to Disordered of BeZnO_2 Alloy

Employing Monte Carlo simulations based on the cluster expansion, the special quasi-random structures and first-principles calculations, we systematically investigate the structure transition of BeZnO_2 alloys from the ordered to the disordered phase driven by the increased synthesis temperature, together with the solid-state phase diagram. It is found that by controlling the ordering parameter at the mixed sublattice, the band structure can vary continuously from a wide direct band gap of 4.61 eV for the fully ordered structure to a relatively narrow direct band gap of 3.60 eV for the fully disordered structure. Therefore, a better optical performance could be achieved simply by controlling the synthesis temperature, which determines the ordering parameters and thus the band gaps.