LMTO能带计算中空原子球和原子空d态的作用

本文研究LMTO能带计算中空原子球和空d态(未填充价电子的d态)的特征和作用。提出一种只在矩阵元计算中计入空d态和空原子球的p、d态的计算方案,在GaAs能带的实际计算中表明,该计算方法把通常求解的36×36阶久期方程减小为10×10阶,仍然得出合理的能带结构,然而,计算效率显著地提高。     

无序对金属超晶格电子结构的影响——CPA方法

本文用一种简单的哈密顿模型,在紧束缚近似下,只计及对角矩阵元的无规分布,用CPA方法自洽地计算了无序所引起的金属超晶格电子结构的变化,给出了某些参数下局部态密度和自能曲线。 关键词：     

应变层超晶格(InAs)n(InP)n(001)电子结构的LMTO计算

基于Linearized-Muffin-Tin Orbitals(LMTO)能带方法,采用内部求和计入空d轨道的处理,对(InAs)_n(InP)_n(001),(n=1,2,3)应变层超晶格的电子结构进行了第一性原理计算。得出了其能带结构,态密度分布(对n=1)。考察了In4d轨道对能带计算的影响,并采用冻结势方法求出了(InAs)_n(InP)_n(001),(n=1,2,3)的价带边不连续值△E_v。 关键词：     

钇在加压下固体电子结构的变化及其超导电性

用自洽 LMTO 方法计算了常压和加压状况下钇的固体电子结构,用 GG 公式计算了在不同压强点钇的电声耦合系数和平均电声矩阵元.结果表明,随着压强的增加,能带电子占据数发生变化,s 分波和 P 分波电荷逐步向 d 分波和 f 分波电荷转移;电声矩阵元中 p(?)d 和 d(?)f 散射项的贡献显著增大,从而导致了 T_c 的迅速升高.     

S-态离子零场劈裂常数α的计算方法

本文考虑到确定S-态离子立方晶场零场劈裂常数a的有效哈密顿矩阵具有与自旋哈密顿矩阵相同的性质,由此导出参数a与L-S表象中有效哈密顿矩阵的非对角元C之间的较简单的关系:a=2/5^1/2C。作为例子,我们从此关系式出发,计算了CaO:Mn²⁺的a值,计算结果与实验值较好地符合。 关键词：     

MnFe2O4晶体的基态能级和零场分裂参量

由不可约张量理论构成一个3d4/3d6离子三角(C3V)对称的晶体场和自旋-轨道相互作用哈密顿矩阵,由这个晶体场和自旋-轨道相互作用哈密顿矩阵被完全对角化后能够求出MnFe2O4晶体中的Fe2+离子的电子顺磁共振零场分裂参量D和F-a,计算了低自旋态(3L态)对电子顺磁共振零场分裂参量(D,F-a)的贡献.结果显示低自旋3L态对电子顺磁共振的零场分裂参量的贡献是较强的.理论计算的结果与实验值是相符的.     

高压下钪的电子结构与超导电性

本文用自洽半相对论 LMTO 能带方法计算了常压、210kbar 和300kbar 下 Sc 的固体电子结构及超导转变温度.结果表明平均电声矩阵元随压强变化是导致 T_c 增长的主要原因.     

OsSi2电子结构和光学性质的研究

采用基于第一性原理的密度泛函理论赝势平面波方法,对正交相OsSi₂的电子结构、态密度和光学性质进行了理论计算,能带结构计算表明它是一种间接带隙半导体,禁带宽度为0813 eV;其价带主要由Os的5d和Si的3p态电子构成;导带主要由Si的3s,3p以及Os的5d态电子构成;静态介电常数ε₁（0）=1543; 折射率n＝393并利用计算的能带结构和态密度分析了OsSi₂的介电函数、吸收系数、折射率、反射率、 关键词： 2')" href="#">OsSi₂ 第一性原理 电子结构 光学性质     

ZnSe∶Fe~(2+)中的动态Jahn-Teller效应和远红外光谱的研究

推导了 3d4 / 3d6离子基态 5D在立方晶体场、自旋 轨道耦合和动态Jahn Teller效应作用下的哈密顿矩阵 ,并用对角化该哈密顿矩阵的方法研究了Fe2 + 在ZnSe中的远红外光谱 ,理论计算与实验符合得好 .研究表明 ,在ZnSe∶Fe2 + 中 ,比晶体场理论分析多出的分裂谱线是Fe2 + 与ZnSe晶格间的动态Jahn Teller效应引起的 .还预测了其它Jahn Teller效应分裂谱 .所推导的哈密顿矩阵对研究 3d4 / 3d6离子在立方晶体中的精细光谱、电子顺磁共振谱和动态Jahn Teller分裂都是有用的 .     

能带论自洽LMTO方法计算金属铜的零温物态方程

 用密度泛函框架下的自洽LMTO方法，在计算一系列晶格常数的Cu的能带结构的基础上，计算了Cu的零温物态方程。压缩度为1.0～4.5。计算结果与两种基于实验数据的半经验方法所得结果以及Albers等人的计算结果进行了比较，其高压部分亦与带量子交换修正的TFC模型结果作了比较，说明计算结果是合理的。进一步的研究可为修正半经验方法提供依据。弄清与TFC理论的异同，对多体系统相互作用有更进一步的了解。     

The origins of phase stability in ordered and disordered Ni-Pt alloys

Using the atomic-sphere approximation formulation of the Korringa-Kohn-Rostoker coherent potential approximation (KKR CPA) method, we have studied the effects of relativity on the electronic structure of ordered and substitutionally disordered Ni-Pt alloys. The inclusion of mass-velocity and Darwin terms are found to be essential for describing the experimentally observed ground-state properties. For the stability of disordered Ni-Pt alloys we find that, in addition to relativity, the minimization of charge-transfer effects are important. We also find that the treatment of ordering tendencies based on the band energy term alone is not sufficiently accurate for alloys with charge-transfer effects. Further analysis, in terms of basis functions, densities of states and non-spherically averaged charge densities, indicate the importance ofs- andd-electrons of Pt for the stability of both ordered and disordered Ni-Pt alloys.     

Ten-fold degenerate d-electron correlation and the metal-nonmetal transition in a disordered binary system: Inclusion of Hund's rule coupling

The Yonezawa-Watabe (YW) study of the metal-nonmetal transitions in nondegenerate, s-electron disordered binary systems: doped semiconductors, metal-ammonia solutions, liquid metals and mixed crystals (alloys), is generalized to include ten-fold d-electron (hole) degeneracy. Such degeneracy automatically includes Hund's rule d-electron coupling and intra-site enhanced Coulomb and exchange interactions. Such a calculation is specifically relevant only to transition metal alloys, transition metal oxides and mixed transition metal oxides. It is seen that potential fluctuations exist in these systems and the possibility of Anderson localization in these disordered degenerate binary transition metal systems is explored. The YW CPA treatment of the effect of substitutional disorder (alloying) upon the mobility gap and quasiparticle states of the density of states at the extreme band edges and localization due to random spin configuration are generalized to these degenerate d-electron systems and it is shown that the disappearance of the mobility gap, not the density of states gap, causes the metal-nonmetal transition for degenerate d-electrons.     

Anisotropic lattice distortions in random alloys from first-principles theory

Within the framework of the exact muffin-tin orbitals (EMTO) theory we have developed a new method to calculate the total energy for random substitutional alloys. The problem of disorder is treated within the coherent potential approximation (CPA), and the total energy is obtained using the full charge density (FCD) technique. The FCD-EMTO-CPA method is suitable for determination of energy changes due to anisotropic lattice distortions in random alloys. In particular, we calculate the elastic constants of the Cu-rich face centered cubic Cu-Zn alloys ( alpha-brass) and optimize the c/a ratio for the hexagonal Zn-rich alloys for both the epsilon and eta phases.     

Remarks on strongly correlated disordered cpa alloys

Strongly correlated disordered metallic alloys are discussed, within Roth's linerization method. We show that the inclusion of the complete Roth's band shift introduce a correlation-induced off-diagonal disorder, which may be treated within the extended CPA approach.     

One-particle properties of compositionally modulated alloys in the coherent potential approximation

We propose a simple generalization of the original single-site coherent potential approximation (CPA) applicable to compositionally modulated alloys. Although the original single-site CPA gives an almost structureless density of states, we find that for strong modulation and relatively strong scattering our generalization of the CPA yields densities of states which exhibit considerable structure and which represent the exact densities of states remarkably well. In this sense our generalization is more accurate than the original CPA from which it was obtained.     

Quick Approximate Calculation on the Transient Temperature Field of Laser Heat Treatment

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重费密子合金的Slave Boson平均场理论

本文从Yoshimori-Kasai模型出发,在Slave Boson平均场范围内采用相干势近似方法,给出一个描述重费密子合金正常态的理论。自洽计算了重费密子合金中传导电子和强关联f电子的态密度随合金浓度的变化。所得结果不仅明确揭示了态密度中赝隙形成的过程,还对重费密子合金中比热和热电功率的低温相干效应作出了合理的解释。     

Phonon density of states of ann-component alloy

We have generalized the coherent potential approximation (CPA) of Tripathi and Behera to the case of ann-component alloy. It is seen that then-component CPA density of states reproduces the binary, ternary quartenary alloys etc when the appropriate limits are adopted.