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.

The activity of zinc oxide in multicomponent slags has been investigated. Activities were determined experimentally Toy equilibrating iron saturated brasses with slags containing iron oxide. Required activities in the Zn-Cu-Fe system were obtained from experimental iron saturation data and available information on the Zn-Cu and Cu-Fe systems. Where measurement was not possible, thermodynamic analyses of slag systems were carried out. Rigid activity patterns in the ZnO-SiO₂, ZnO-FeO-SiO₂, ZnO-CaO-SiO₂ and ZnO-FeO-CaO-SiO₂ systems have been developed from experimental and analytical data. Agreement with the activity data of Bell, Turner and Peters on ZnO-FeO-CaO-SiO₂ and Okunev and Bovykin on ZnO-FeO-SiO₂ type slags indicates that the present measurement technique provides a good basis for industrial slag investigations. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The activity of ZnO in ternary Zno-CaO-SiO₂ slags has been measured at 1300 C by equilibration with copper rich brass and low oxygen potential gas utilizing the following reversible galvanic cell: Pt I H₂,H₂O |0.85Zr0₂-0.15CaO | 0₂(Air)|Pt Thermodynamic data on the component binaries was employed to calculate the excess free energy of the ternary system and the isoactivity patterns of the three components at 1600 C with respect to the metastable pure liquid standard states. An estimate of 6 E.U. was made for the entropy of fusion of ZnO. The measured activities are in good agreement with the calculated values. The proposed excess free energy contours in the Zno-CaO-SiO₂ ternary are similar in shape to those calculated in a similar manner for the FeO-CaO-SiO₂ system. Also the calculated zinc oxide isoactivity figure resembles the ferrous oxide isoactivity diagram. This zinc oxide isoactivity pattern projects towards the lime orthosilicate composition. This shape is characteristic of FeO, but in the case of ZnO the projection is less pronounced. Both these observations are in keeping with the slightly more basic behaviour of zinc oxide. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis (Ph. D.)--University of Canterbury, 2010. / Typescript (photocopy). "February 2010." Includes bibliographical references (p. 168-181). Also available via the World Wide Web.

The separation of oxidation-reduction reactions into individual half-cells with a resulting "mixed potential" is well known as a dissolution mechanism for metals; however, the mechanism by which non-conducting crystals lose ions to the solution has been studied only slightly.

Graduation date: 1994

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2006. / Wang, Zhong Lin, Committee Chair ; Summers, Christopher J., Committee Co-Chair ; Wong, C. P., Committee Member ; Dupuis, Russell D., Committee Member ; Wagner, Brent, Committee Member

published_or_final_version / abstract / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / abstract / Physics / Master / Master of Philosophy