【作者】 何开华；

【导师】 颜其礼； 姬广富；

【作者基本信息】 四川师范大学 ， 凝聚态物理， 2005， 硕士

【摘要】 运用局域密度泛函理论可将多电子系统转化为单电子系统,由此对各类半导体材料和金属材料的结合能、晶格常数、体变模量做计算得到了与实验符合很好的结果,使之成为近年来电子理论中的一项重要的成就。过去固体实验工作积累了大量的实验数据,目前大型、高速电子计算机的应用,使得此理论的优越性也显得越来越突出。能带理论的研究是从定性的普遍性规律发展到对具体材料复杂能带结构的计算。在密度泛函理论的框架下,出现了很多算法,常用的有基于原子轨道线性组合的紧密束缚法(LCAO.TB)、正交平面波(OPW)、赝势平面波(PWP)、线性缀加平面波方法(LAPW)、线性Muffin-tin 轨道组合方法(LMTO)等等。本论文工作重点讨论了超软赝势平面波方法在典型半导体材料研究中的应用。本论文主要进行了以下三个方面的研究工作: 1、用基于密度泛函理论的平面波赝势方法,计算了在各向同性压力下闪锌矿结构(ZB)和岩盐结构(RS)的BN、BP 和BAs 的电子结构和总能。交换关联能函数分别用了局域密度近似和广义梯度近似来描述。对这三种化合物的两种结构分别进行了几何优化,得到了其平衡晶格常数和体模量。由总能和体积的曲线得到了发生相变的压强和体积。另外,还发现在BN 与BP、BAs 之间存在三处差异:第一、BN 的硬度要比其它两种要高很多;第二、BN 的带隙随着压力的增大而增大,BP 和BAs 却有相反的趋势;最后一处差异是电子的转移方向不同,在BN 中B→N,而在BP 和BAs 中P→B 、As→B。更多还原

【Abstract】 Density function theory, as we know, can deal multi-electron system with single-electron system. Binding energy、lattic constants 、bulk modules were presented based on density function theory of semiconductor and metal materials. These results were in a very good agreement with experiments. Theory calculation was an important achievement in electronic theory. A lots of experiments data were obtained and the large、quick computers were also developed in recent years. The calculations by simulating are becoming more and more powerful, and the theory resulted the research of energy band from develop qualitative universal disciplinarian to the complex band structure of typical materials. There are much arithmetic based on density function theory. Such as LCAO-TB、OPW、PWP、LAPW and LMTO, etc. The PWP was used in this thesis. In this thesis, the main research works can be divided into three parts: 1 The plane-wave pseudopotential method within the local-density approximation and generalized gradient approximation was used to investigate the effect of hydrostatic pressure on the structures of BN、BP and BAs. For each compound, two phases were considered: Zincblend(ZB) and Rocksalt(RS). We optimized their structures and obtained the equilibrium lattic constants and bulk modulus. The total energies as functions of volume indicated the transition pressures and transition volumes. These results were in well consist with experimental values and some theoretical works, the discrepancy between our results and some theoretical works come from the computed method. From the bond property of these compounds, we interpreted the reason why BN was more harder than BP and BAs was. We also obtained the relation of band gaps versus pressure for ZB structure. It was found that the indirect band gap of BN increased with decreasing volume, but inversely for BP and BAs. 2、Electronic structure and total energy of BN, AlN and GaN (with wurtzite structure) have been computed by means of plane wave pseudo-potential method (PWP) with GGA and LDA. We obtained the lattice constants and elastic moduli by using GGA and LDA. We found that the lattice constants were in good agreement with experiments, Elastic moduli which deduced by using LDA was closer to experiments than that of using GGA one. Every compound’s band gap and absorption coefficient under pressure were obtained and compared with experiments. 3、Electronic structure of ZnS: V supercell was computed by means of plane wave pseudo-potential method(PWP) with generalized gradient approximation(GGA). The optical property was studied and the calculation results were in consist with the values calculated by the theory of crystal field and with the experiment results. Through doping impurity, we found that the energy level has a shift about -2.5ev. The Mulliken charge of V was 0.28, which was smaller than Zn. The covalence of bond S-V was strongest than that of other bonds, since the bond length was the shortest.更多还原