近年来，过渡金属硫族化合物因具有与石墨烯类似的层状结构且属于天然的半导体材料而受到半导体材料与器件领域学者的重视，成为相关领域的研究热点之一。本文基于密度泛函的第一性原理，重点针对过渡金属硫族化合物中的杰出代表WSe2进行研究。计算了WSe2在外应力、不同掺杂以及和其它材料固溶条件下的稳定性和光电性质，所得结论如下：1. 外应力对WSe2的晶体结构、电子结构和光学性质具有十分重要的影响。研究发现：在外应力作用下WSe2的体积、晶格常数a和c都随外应力的增加而减小，计算对比说明WSe2沿c柱方向更容易被压缩。随着外应力的增加该物质的禁带宽度逐渐减小，最终在35GPa时由半导体转变成了金属。当外应力由0GPa增加到60GPa时，WSe2的静态折射率由原来的3.8增加到了4.5，静态消光系数始终为零，静态介电函数的实部由14.5增加到了20，虚部始终为零。由WSe2的吸收谱我们发现从可见光到紫外光区WSe2都表现出很强的吸收能力，在外压的作用下它的吸收能力进一步增强并且吸收范围向深紫外区移动。2. 由Mo、Se掺杂2H-WSe2体系(RMo-WSe2、IMo-WSe2和RS-WSe2)发现在三种掺杂体系中RMo-WSe2和RS-WSe2的c参数均变大了IMo-WSe2的c参数却变小了，这是由于IMo-WSe2体系中Mo原子与邻近的Se原子成键从而拉近了层间距。研究还发现在2H结构中，夹层掺杂体系的形成能最高体系稳定性最差，虽然Mo与W原子差距很小但是掺杂方式的不同体系的稳定性差距很大，说明层间的范德瓦耳斯力不允许外来原子的侵入。对电子结构的研究我们发现，RMo-WSe2和RS-WSe2体系的带隙都随着杂质原子的介入变宽了，而只有IMo-WSe2体系的禁带宽度减小到了0.071eV，有向金属性转变的趋势。通过(1 1 0)面上总电荷密度图的分析可知Mo原子与Se原子电子轨道杂化形成共价键，层内的部分电子局域到夹层中使得材料有从半导体向金属转变的趋势。3. 我们用S原子和Se原子之间替换的方式，建立了固溶体模型WS2(1-x)Se2x(x=1/3,1/2,2/3)。通过对材料的晶体结构的分析可知WS2(1-x)Se2x中Se作为溶质原子的加入WS2中后引起晶格的畸变程度较小，结构稳定性较高，容易形成固溶度较大的连续固溶体WS2(1-x)Se2x(x=0~1)。通过对几何结构优化之后的晶体结构进行分析可知，随着溶质原子Se组分比的提高，晶格常数a逐渐增大，导致晶胞体积也随Se组分比的增加而增大。对键长的调查发现键长dW-S小于dW-Se，由夹层原子间距可知：dS-S ﹀

In recent years, Transition-Metal Dichalcogenide Compounds (TMDCs), which is similar to Graphene layer structure and belong to natural semiconductor materials, attract the attention of scholars in the field of semiconductor materials and devices and become one of the research areas. In this paper, the first principles based on the density functional theory were performed to discuss the outstanding representatives in TMDCs, WSe2. We investigate the stress, doping and WS2(1-x)Se2x alloys effects on stability and electronic structure. The conclusion is as follows:1. External stress has a great effect on the crystal structure, electronic structure and optical properties of WSe2. Studies found that the lattice constant a, c and volume decreases with the increase of external stress, WSe2 more likely to be compressed along the c direction, with the increase of stress the band gap of WSe2 decreases and when the stress is 35GPa，WSe2 becomes metal. Studies of external stress effects on WSe2 optical properties found with stress increases from 0GPa to 60GPa, refractive index increases from 3.8 to 4.5, extinction coefficient is always 0, the real part of dielectric function increases from 14.5 to 20, imaginary part is always 0. From the absorption spectrum we find WSe2 showed a strong absorptive capacity from visible light to ultraviolet area. Under the action of external pressure, its absorptive capacity is further strengthened and move to the deep ultraviolet absorption range.2. Mo, Se doped 2H-WSe2 has three kinds of configurations (RMo-WSe2, IMo-WSe2 and RS-WSe2), the investigation in three doped systems shows of c parameters in RMo-WSe2 and RS-WSe2 are more than pure WSe2, but in IMo-WSe2 system the bond of Mo and adjacent Se atoms makes c parameter smaller. The calculation results show IMo-WSe2 with a Mo atom embedded into the interlayer, its formation energy is maximum and stability is worse than RMo-WSe2 with one of W atoms replaced by a Mo atom, which implies it is more energetically favorable that one W atom is substituted than that one Mo atom is embedded into the interlayer of the 2H-WSe2 supercell. The calculation results of electronic structure show the band gap of RMo-WSe2 and RS-WSe2 is wider than pure system, but the band gap of IMo-WSe2 is 0.071eV and become narrow, it has the trend of being metal. The results of the total charge density on the (1 1 0) surface for the two doping systems show the doped V atom and adjacent Se atoms form coordinate bonds from shared electrons.3. WS2(1-x)Se2x(x=1/3, 1/2, 2/3) solid solutions are formed by Se atoms replace S atoms. In WS2(1-x)Se2x systems, Se atoms as solute atoms into WS2 bring small lattice distortion degree and easy to form a stabile structure. The analysis based on the optimization of geometric structure shows with the increase of concentration of Se doping, the lattice constant a increased gradually, leading to cell volume also increases with the increase of concentration. To study the structure of the solid solution, we find its surface different from pure WS2 or WSe2 is not smooth, the surface atoms are no longer in the same plane. The calculation results of electronic structure show the band gap of WSSe is narrower than the gap of WS4/3Se2/3 and WS2/3Se4/3, but the band gap of all WS2(1-x)Se2x(x=1/3, 1/2, 2/3) solid solutions is wider than WSe2, narrower than WS2. It can be seen WS2(1-x)Se2x(x=1/3, 1/2, 2/3) solid solution without changing the character of the direct band gap of pure WSe2 and WS2, can effectively adjust the band gap width.Key Words: First Principles, WSe2, Stress, Doping, Solid SolutionsType of Dissertation: Applied Basic Technology