P,N影响Fe晶界结合的第一原理研究

本文利用第一原理离散变分方法,计算了轻杂质Ｐ、Ｎ在体心ＦｅΣ３（１１０）（１１１）晶界和Ｆｅ（１１１）表面的偏聚能,从能量方面对Ｐ、Ｎ的韧脆机制进行了探讨。结果表明,Ｐ在晶界上的偏聚能比表面上更高,更有利于偏聚在表面而非晶界,而Ｎ则相反。因此,Ｐ为脆性杂质,Ｎ为韧性杂质,此结果与实验观察相符,还分析了造成这一结果的化学因素和力学因素的影响,指出了在计算中对原子结构进行弛豫的必要性。     

非谐振子的高阶压缩

随着高阶相关测量技术的发展,量子电磁场的高阶压缩的研究引起了人们的重视。1985年Hong和Mandel提出了量子场高阶压缩的概念,并计算了简并参量下转换、二次 谐波的产生等过程中场的高阶压缩。本文重点研究非谐振子的高阶压缩。 相干光通过非吸收的光学双稳非线性介质,光场与介质相互作用,其物理模型为非谐振子,此系统的哈密顿量为     

Electronic structures of nickel metal with hydrogen impurity

By using a first-principles numerical method, the electronic structures of face-centered cubic Ni doped with H, H+ and H- are investigated. In two adopted cluster models, H occupies the centers of octahedron and tetrahedron as interstitial. It was found that the former is preferentially occupied. The constructed Ni-H, Ni-H+ and Ni-H- bonds are only slightly different due to electron flowing. The residual (doping H-) or insufficient (doping H+) electrons are basically absorbed or supplied by the further matrix atoms. The additions induce a strong reduction of the interactions between their first neighbor atoms, but a weaker alteration of those between their first and second neighbors, which is the expression of hydrogen local effect and can be regarded as an explanation of hydrogen embrittlement.