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Zno Material Phase Transformation Mechanism

Posted on:2011-02-21Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhuFull Text:PDF
GTID:2208360305959564Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
First principles calculations and the plane-wave method are carried to study the structural stability of wurtzite ZnO by optimizing the Ecutoff, the SIGMA, the K grid, and the lattice constant step by step. To optimize the atomic position, we use scanning methods to get a potential energy surface about the lattice constants c/a and a. The lowest point of the potential energy surface corresponds to the most stable structure, where the lattice constants ratio c/a is 1.6256. Comparing the five pseudopotential, the USPP functional and the PW91 pseudopotential were selected to the following calculations of the WZ ZnO. Based on the above calculations, we study the elastic constants, the band structure and the density of states etc material properties, and analysis and discuss them by comparing with the results of previous.The study of three-phase relationship between the phase transition were our main works. We focus on the transformation from WZ to ZB, because there have been already existed the phase transition barrier, the transition pressure and the transformation path from WZ to RS of ZnO, at the same time the phase transition barrier and the transformation path from ZB to RS of CdSe, ZnS, SiC, InP etc were studied and reported, further more a mesophase was discovered between ZB and RS. This article showed the transformation path from ZB to WZ, and the phase transition barrier. The energy barrier was calculated for homogeneous transformation for different ZnO transformation pathways. From all the transformation pathways, a most probable pathway is proposed whose energy barrier (0.19eV/pair) is lower than any other pathway. Compared with the energy barrier between wurtzite and rock salt (0.15eV/pair), the energy barrier in this work is not obvious difference from it. Furthermore, compared with the energy barrier of GaN(0.26 eV/pair), the energy barrier in this work is obvious lower than it. Therefore, it is possible to transfer from zinc-blende to wurtzite with respect to the energy barrier. This work accounts for why it is impossible to transfomate directly between wurtzite and zinc blende in thermodynamic aspect and dynamical aspect, just because of lacking of phase transformation driving force.
Keywords/Search Tags:ZnO material, VASP software, wurtzite structure properties, three-phase relationship
PDF Full Text Request
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