【作者】 王毅；

【导师】 李有勇；

【作者基本信息】 苏州大学 ， 材料学， 2011， 硕士

【摘要】 氧化锌(ZnO)具有优异的光学、电学性质,由于其广阔的应用前景,引起了人们极大的关注。掺杂元素是改变其固有性质、提高应用性能的有效途径。我们利用密度泛函理论(DFT)研究过渡元素掺杂氧化锌的掺杂效应,计算结果发现随着过渡元素掺杂,氧化锌B4结构向B1结构的相转变压力降低,这个结果与同步辐射得到的原位高压X射线粉末衍射结果一致。主要研究内容如下:(1)采用广义梯度近似(GGA)泛函计算ZnO的纤锌矿结构(B4)、闪锌矿结构(B3)、岩盐矿结构(B1)的几何结构、晶格参数、能带结构、电子结构、不同压力对电子结构的影响,特别是系统研究了ZnO的相变,利用压力-焓曲线得出B4结构与B1结构、B4结构和B3结构、B1和B3结构之间的相转变压力。(2)利用密度泛函理论(DFT),我们系统的研究了ZnO相转变过程中可能存在的过渡态中间相,从压力-焓曲线方面进行研究,对于过渡元素Mn掺杂ZnO体系,我们以过渡态中间相为依据,系统研究Mn掺杂对ZnO相转变的影响,并结合过渡态中间结构对于Mn的掺杂效应作了详细阐述,ZnO材料和Mn掺杂ZnO体系的这些计算模拟结果可以为实验及材料的生长合成提供合理的理论依据。(3)通过第一性原理计算了Co掺杂对ZnO相转变的影响,从掺杂对相转变压力、过渡态势垒、态密度、体积膨胀率等方面进行研究,发现掺杂效应对ZnO的影响顺序:B1 < intermediate tetragonal < intermediate hexagonal < B4(4)对于Mn或Co引起的强相关联作用,我们利用DFT+U计算了Mn掺杂对ZnO相转变的影响,DFT+U计算结果与采用DFT的计算结果相一致。更多还原

【Abstract】 Since ZnO shows excellent optical and electrical properties and has various applications in our daily life, this material has become one of major focuses in the research field. Doping in ZnO is one of the most efficient approaches to improve its performance. We use DFT method to systematically study the doping effect of transition element on ZnO. Our calculation results show that the transition pressure from the wurtzite (B4) phase to rocksalt (B1) phase of ZnO decreases with transition element doping, which is consistent with in situ high pressure X-ray powder diffraction results from synchrotron radiation. We outline our studies and results as follows:Firstly, we performed the geometry optimization and calculated the lattice parameters, band structure, the effect of different hydrostatic pressures on ZnO using the density functional theory(DFT) framework, based on the plane wave basis set and ultra-soft pseudo-potentials with the generalized gradient approximation(GGA) functional. We pay due attention to the transition pressure from the wurtzite (B4) phase to rocksalt(B1) phase, the znic blend(B3) phase to rocksalt (B1) phase, the wurtzite(B4) phase to the zinc blende(B3) phase of ZnO, respectively.Secondly, DFT method was used to find the transition intermediate structures and then we systematically study the doping effect of Mn on the phase transition of ZnO based on our proposed transition intermediate structures. Our results provide a theotetical basis for doping approach to control the structure and properties of ZnO and other similar materials.In addition, in consideration of strong correlated interactions, DFT+Hubbard U was applied to calculate the doping effect of Mn on the phase transition of ZnO and We found that our DFT+U results are consistent with our DFT results.更多还原