At present , the studies on this are mainly focus on the surface geometry structure . little is payed for the electronic structure . in this dissertation , the surface properties of high miller index surface of metals and semiconductors were studies by using the molecular dynamics method , the scattering theoretical method and the ab initio quantum mechanical molecular dynamics simulations 金属和半导体材料的高密勒指数表面是目前表面科学研究的一个热点问题，也是值得更进一步研究的问题，目前的研究主要集中在对表面几何结构的确定，而对表面电子特性的认识几乎很少涉及，本文根据目前实验上对一些表面已有的研究结果，在理论上对一些金属、半导体的高密勒指数表面的表面能和表面电子结构进行了研究。
We have calculated one - and two - photon absorption cross sections of the lowest excited states of a series of molecules combined with benzene , stilben , thiophene as center attached with amine , diphenylamine , diethylamine as electron - donor and nitryl as electron - acceptor ; the effects of molecular length , n center and electron - donor on two - photon absorption cross sections have been studied and all calculations have been carried out using the density functional theory at an ab initio level . it is found that the molecular length and the one - photon absorption intensity are quite strongly c orrelated factors , and that a corresponding correlation for the two - photon absorption is decreasing . it is also found that a most crucial role for the two - photon absorption is played by the n center 我们分别以苯、二苯乙烯、噻吩为中心，氨基、二苯氨基和二乙氨基为电子给体，硝基为电子受体组合形成的分子为研究对象，在从头计算的水平上用密度泛函理论计算了这些分子在低激发态下的单、双光子吸收强度，重点研究了分子的长度、中心和给体的供电子能力对分子单、双光子吸收的影响。研究结果表明，分子长度与单光子吸收强度之间有密切关系，而在双光子吸收中这种关系较弱；中心在双光子吸收中具有重要的作用；在中心和受体一定的情况下，增加给体的供电子能力，可提高双光子吸收强度。
The elastic constants of bcc li , na and fcc al crystals have been evaluated as functions of pressure and temperature by using a new model together with ab initio electronic structure and total - energy calculations . in the model it is considered that the elastic constants of crystals at a given temperature and pressure can be calculated using a conventional density functional method but modified by a new set lattice constants due to the isobaric volumetric thermal expansion when temperature rise from absolute zero to the given one 本文对高压及有限温度立方金属弹性常数的计算方法进行了研究，建立了一种考虑温度效应的物理模型，基于这个模型和从头算方法，对典型的立方晶系金属li 、 na 、 al在高压及有限温度(熔点以下温度)弹性常数进行了计算，取得了与已有实验结果较好相符的计算结果。
