Computational study of the structural phase transitions and pressure dependent electronic structure of ZnO

摘要

We use rst-principles calculations based on density functional theory to study theudstructural properties and pressure-induced solid-solid phase transitions of ZnO. Bothudthe local-density approximation (LDA) and the PBE96 form of the generalized gradi-udent approximation (GGA) are employed together with the projector augmented waveud(PAW) method to mimic the electron-ion interaction. The electronic structure isudinvestigated by the HSE hybrid functional and a partially self-consistent GWapprox-udimation. We consider the wurtzite (B4), rocksalt (B1), zinc blende (B3), CsCl (B2),udPbO (B10), NaTl (B32), WC (Bh), BN (Bk), NiAs (B81) and AsTi (Bi) modi cationsudof ZnO. The calculated structural properties in the B4, B3, B1 and B2 phases compareudacceptably well with those found in previous theoretical studies, as is the transitionudpressure between them. We nd that the B4 phase is the most preferred low-pressureudcandidate in ZnO while the B2 phase is favorable at high pressures. Apart from theudpreviously reported B4!B1!B2 phase transition, our study reveals other possibleudpaths for a transition from B4 to B2 phase with the Bk, Bh, B10, and B81 structuresudas intermediate phases. It is found that the HSE and the GW approach o¤er a signif-udicant improvement to the prediction of band-gaps in ZnO. The band-gaps are foundudto increase with increasing pressure leading to the structural phase transitions.