ZnO是一种典型的II-VI族金属氧化物半导体，禁带宽度约为3.37 eV，具有物理化学性质稳定、廉价易获得、环境友好无污染等优点。ZnO是一种具有开发潜质的光电子材料和稀磁半导体，在国际学术界备受关注。众多研究报道已经证实，掺杂改性是改善ZnO物理化学性质的有效手段，改性后的ZnO其磁学和光电子特性均有显著提高。然而，目前Cd／W单掺以及Al掺杂和点空位在ZnO体系中的掺杂机理尚不明确，体系中的磁性响应机制还不清楚，相关的研究结论存在争议。Cd／W掺杂对ZnO吸收光谱及磁性影响的研究仍存在分歧，对于应力对Cd／W掺杂ZnO光学性质和磁性能影响的研究鲜见报导，Al掺杂和点空位对ZnO磁性来源的研究存在不同的解释。 本文基于第一性原理方法，使用Materials Studio 8.0软件包中的CASTEP模块，采用密度泛函理论(DFT)，广义梯度近似(GGA+U)平面波超软赝势方法，建立了Cd掺杂ZnO模型(杂质浓度范围：0.02083-0.03125)；W掺杂ZnO模型(杂质浓度范围0.0417-0.0833)；Al掺杂和空位(Zn空位／O空位)共存ZnO模型。对各个模型进行几何结构优化，在此基础上对优化结构的电子结构、自旋特性、电荷布居值、差分电荷密度、光学和磁学性质等进行了计算。通过对计算结果的分析研究得到如下结论： 随着Cd掺杂量增加，掺杂体系中离子之间的Cd-O和Zn-O键长变长，吸引力变小，排斥力变大，体积变大。Cd掺杂量越多，系统形成能越大，掺杂越困难，结构稳定性下降。Cd-5s轨道引入的杂质能级在znO能带中构成新的导带底，随着Cd掺杂量增加，Zn-4s轨道和Cd-5s轨道杂化耦合效应越增强，s-s轨道成键越增强，掺杂体系的禁带宽度越窄。其相应的吸收光谱发生红移，即Cd掺杂ZnO体系与纯ZnO相比具有更高的可见光吸收率。压应力和拉应力均使体系形成能增加，稳定性下降，带隙变窄，吸收光谱红移，并且体系无磁性。 随着W掺杂量增加，体系形成能降低、稳定性增强。W掺杂能有效降低ZnO的禁带宽度，杂质浓度越大，禁带宽度越小。W-5d轨道、O-2p轨道和Zn-3d轨道杂化耦合电子交换作用使ZnO具有铁磁性。但随着W掺杂量的增加，体系产生磁性猝灭现象。这种磁性结构的居里温度能够达到室温以上。应力使得体系的形成能增加，稳定性下降，带隙变窄，吸收光谱红移增强。压应力使得体系的总磁矩先增大后减小，拉应力使得体系的总磁矩减小。压应力使得体系的居里温度先升高后降低，拉应力使得体系居里温度降低。 对于Al和点空位共存的ZnO体系而言，由于Al离子的半径小于Zn离子半径，Al替代Zn掺杂导致ZnO晶格体积变小。单纯的Al掺杂并未使ZnO体系产生磁性。但Al掺杂易在Al离子附近位置引起空位，O空位对体系磁性没有贡献，但Zn空位导致的空穴可作为媒介使O-2p轨道和Zn-4s轨道发生交换关联作用进而使体系具有铁磁性。这种磁性机制能使ZnO具有室温铁磁性。 关键词：第一性原理计算；掺杂ZnO；稀磁半导体；电子结构；吸收光谱

 ZnO (a typical II-VI metal oxide semiconductor with a band gap of about 3.37 eV.) is valued for its stable physical and chemical properties, low cost and easy availability and environmental friendliness and non-pollution. ZnO as a potential optoelectronic material and dilute magnetic semiconductor, has been focused by the researchers around the world. Numerous studies have confirmed that doping modification is an effective approach to improve the physicochemical properties of ZnO. The magnetic and optical properties of the modified ZnO are significantly improved. However, the doping mechanism is still unclear about Cd/W single doped ZnO and A1 doped ZnO with point vacancies. The current research findings are not in agreement. There is a divergence in the influence of Cd/W doping on the absorption spectrum and magnetic property of ZnO, and the study of stress on the optical and magnetic properties of Cd/W doped ZnO are rarely reported. The magnetic source and mechanism are explained differently in doped ZnO systems with A1 doping and point vacancies. Based on the first-principles approach and employing the CASTEP module in the Materials Studio 8.0 software package, this work applied Generalized Gradient Approximation (GGA +U) Planwave-Pseudopotential method of Density Functional Theory to establish models of Cd (concentration range: 0.02083-0.03125) doped ZnO, W (concentration range: 0.0417-0.0833) doped ZnO and Al doped ZnO with and without vacancy (Zn vacancy or O vacancy). After optimizing the geometric structure of all the models, the electronic structure, spin characteristics, charge population, difference charge density, optical and magnetic properties of them were calculated. Through the analysis of the calculation results, the following conclusions are obtained. The Cd-O and Zn-O bond lengths in the doping system become longer with the increasing of Cd doping amount, the attractive force became weaker, the repulsive force became stronger, and the volume became larger. The more Cd was added, the greater the system formation energy became, the more difficult the doping was and the lower the structural stability was. The impurity level introduced by the Cd-5s orbit constitutes a new conduction band minimum of ZnO .With the increasing of Cd doping amount, the hybridization coupling effect of Zn-4s orbit and Cd-5s orbit became stronger. The band gap decreased due to the enhanced bonding state between s-s orbits, and the redshift appeared in its absorption spectrum, which means the visible light absorption of ZnO increases. The formation energy of the system with both compressive and tensile stresses increased, the stability decreased, the band gap narrowed, the absorption spectrum red shifted, and the systems was nonmagnetic. The formation energy of the system decreased and the stability increased with the W content increasing. W doping effectively reduced the band gap of ZnO. The higher the impurity concentration was, the narrower the band gap. W doped ZnO is ferromagnetic because of the hybrid coupling exchange among W-5d orbit, 0-2p orbit and Zn-3d orbit. With the increasing of W content, magnetic quenching occurredin the system. The Curie Temperature of this magnetic structure can reach room temperature. The formation energy of the system with both compressive and tensile stresses increased, the stability decreased, the band gap narrowed, and the absorption spectrum was characterized by redshift. The magnetic moments increased first and then decreased with the compressive stress increasing, and decreased with the tensile stresses increasing. The Curie Temperature decreased with the tensile stresses increasing and increased first and then decreased with the compressive stress increasing. For the ZnO system in which A1 and point vacancies coexist, since the radius of the A1 ions is smaller than the Zn ion radius, the substitution of A1 for Zndoping resulted in reduction of ZnO lattice volume. Pure A1 doping does not make the ZnO system magnetic. However, A1 doping easily causes vacancies in the vicinity of A1 ions. O vacancies didn’t contribute to the magnetic moments of the system, while Zn vacancies made the system ferromagnetic. There was an exchange interaction between 0-2p orbit and Zn-4s orbit with hole-media induced by Zn vacancies. This magnetic mechanism enables ZnO to possess room temperature ferromagnetism. Key words: First-principles Calculation; Doped ZnO; DMS; Electronic structure; Absorption spectrum