We use rst-principles calculations based on density functional theory to study the
structural properties and pressure-induced solid-solid phase transitions of ZnO. Both
the local-density approximation (LDA) and the PBE96 form of the generalized gradi-
ent approximation (GGA) are employed together with the projector augmented wave
(PAW) method to mimic the electron-ion interaction. The electronic structure is
investigated by the HSE hybrid functional and a partially self-consistent GWapprox-
imation. We consider the wurtzite (B4), rocksalt (B1), zinc blende (B3), CsCl (B2),
PbO (B10), NaTl (B32), WC (Bh), BN (Bk), NiAs (B81) and AsTi (Bi) modi cations
of ZnO. The calculated structural properties in the B4, B3, B1 and B2 phases compare
acceptably well with those found in previous theoretical studies, as is the transition
pressure between them. We nd that the B4 phase is the most preferred low-pressure
candidate in ZnO while the B2 phase is favorable at high pressures. Apart from the
previously reported B4!B1!B2 phase transition, our study reveals other possible
paths for a transition from B4 to B2 phase with the Bk, Bh, B10, and B81 structures
as intermediate phases. It is found that the HSE and the GW approach o¤er a signif-
icant improvement to the prediction of band-gaps in ZnO. The band-gaps are found
to increase with increasing pressure leading to the structural phase transitions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/11941 |
| Date | 12 September 2012 |
| Creators | Molepo, Mahlaga Phineas |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
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