Self-consistent electronic structure of quantum wells by invariant embedding method

A new approach based on the invariant embedding method for the self-consistent calculation of electronic structure of quantum wells is presented and is applied to both neutral quantum well and parabolic quantum well. Numerical results obtained for these structures agree very well with those of previous theoretical and experiment studies. The present approach is expected to lead to a more efficient and stable scheme for the calculation of electronic band structure of quantum structures. Realistic boundary conditions are naturally taken into account in the present calculation which provides a convenient way for studying boundary effects. Received 21 September     

Analytic form of Thomas-Fermi-Dirac dielectric function for Si,Ge and diamond by variational method

The nonlinear Thomas-Fermi-Dirac equation is solved by a variational method for the positive and negative point charges in silicon, germanium and diamond. With the parameters determined, approximate analytic form is presented for the spatial dielectric function. Comparison with numerical result is indicated.     

Self-consistent electronic structure and ground state properties of TlCl

We present the first self-consistent, relativistic, ab initio calculation of the electronic structure, equilibrium lattice constant, cohesive energy and compressibility of TlCl, as an example of a semiconductor with high atomic number and high ionicity. The theoretical approach is based on the local density-formalism. Our results explain the salient features of recent photoemission measurements and describe the ground-state properties with good accuracy.     

SCF-Xα studies of the electronic structures of C,Si and Ge oxides

SCF-Xα scattered wave cluster MO calculations are presented for the oxyanions CO₃^?2, CO₄^?4, SiO₃^?2, SiO₄^?4, SiO₆^?8, GeO₄^?4 and GeO₆^?8. A comparison of the calculations with available X-ray spectral data shows good agreement. The MO diagrams for CO₃^?2 and CO₄^?4 are found to be quite similar, suggesting that the four coordinate oxyanion is not inherently unstable; therefore a quartz polymorph of CO₂ may become stable at high pressure. On the other hand, the valence region width of SiO₃^?2 is much smaller than that of SiO₄^?4; thus the three-coordinate Si oxyanion is expected to be highly unstable. For the Ge oxyanions the average valence region width is substantially larger in the six-coordinate than in the four-coordinate form, suggesting a preference for octahedral coordination. These observations indicate that although the valence region width is only one factor affecting the total energy of a system, it is predictive of favored coordination number according to the following principle: a change from a higher to a lower coordination number oxyanion of a given cation, Mⁿ⁺, will be favorable if the lower coordinate form has a wider valence region at its equilibrium internuclear distance.     

Si，Ge，Zr和Sn掺杂SrTiO3的电子结构和光催化性能第一性原理研究

使用QUANTUM ESPRESSO(QE)软件包实现的密度泛函理论研究了Si, Ge, Zr和Sn掺杂SrTiO₃的结构,电子结构和光催化性能.使用广义梯度近似(GGA)获得SrTiO₃的晶格常数与先前的实验数据非常一致.同时,获得了SrTi_0.875X_0.125O₃(X=Si, Ge, Zr, Sn)四种掺杂体系的晶格常数. SrTiO₃和SrTi_0.875X_0.125O₃(X=Si, Ge, Zr, Sn)四种掺杂的带隙值分别1.853 eV、1.849 eV、1.916 eV、1.895 eV和1.925 eV.在研究五种SrTiO₃体系的光催化性能时,采用剪刀算符对五种SrTiO₃体系的带隙值进行修正.计算本征SrTiO₃和SrTi_0.875X_0.125O₃     

Self-consistent calculation of the electronic structure of small jellium spheres

A self-consistent, density functional calculation of the electronic structure of small metal spheres is reported. The jellium model of a metal where the positive ions are replaced by a uniform positive background is used in the calculation. The electronic structure, ionization potential and electron affinity are computed for spheres containing from 4 to 196 electrons.     

第一性原理计算Ga,O掺杂Ge材料的电子结构

利用第一性原理模拟计算了Ga掺杂Ge及Ga、O共掺杂Ge材料的电子结构,对态密度、能带结构进行了分析。结果表明,Ga掺杂Ge材料会使掺杂体系表现为较强的金属性;Ga、O共掺杂会使掺杂体系在低能端出现新的禁带区域。通过掺杂能够改变Ge材料的电学和光学特性。     

Self-consistent calculation of the band structure of copper by the LMTO method

Conclusion In our paper we have presented an effective self-consistent procedure which has been applied to the calculation of the electronic structure of copper. The results attest to the high stability of this procedure. The method of previously attaining atomic self-consistency makes possible a substantial reduction of the volume of band-structure calculations and, therefore, of the total time of the SC procedure. It has thus become possible to carry out calculations with good accuracy for a number of physical properties and the binding energy of metals on medium-sized computers. It must be pointed out that the self-consistent calculation of the band structure with prior attainment of atomic self-consistency is also possible in other methods of constructing the band structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 103–107, July, 1983.The authors are grateful to Yu. Kh. Velikov and E. G. Maksimov for their attention and advice.     

第一性原理研究[112]硅锗异质结纳米线的电子结构与光学性质

基于密度泛函理论体系下的广义梯度近似,本文利用第一性原理方法着重研究了[112]晶向硅锗异质结纳米线的电子结构与光学性质.能带结构计算表明:随着锗原子数的增加,[112]晶向硅锗纳米线的带隙逐渐减小;对Si_(36)Ge_(24)H_(32)纳米线施加单轴应变,其能量带隙随拉应变的增加而单调减小.光学性质计算则表明:随着锗原子数的增加,[112]硅锗纳米线介电函数的峰位和吸收谱的吸收边均向低能量区移动;而随着拉应变的增大,吸收系数峰值呈现出逐渐减小的趋势,且峰位不断向低能量区移动,上述结果说明锗原子数的增加与施加拉应变均导致[112]硅锗纳米线的吸收谱产生红移.本文的研究为硅锗异质结纳米线光电器件研究与设计提供一定的理论参考.     

Energy band structure and thermo-mechanical properties of tungsten and tungsten carbides as studied by the LMTO-ASA method

The calculations of the energy band structures of W (b.c.c. lattice), WC (f.c.c. and h.c.p. lattices) and W₂C have been performed by the LMTO-ASA method. The results of the band structure calculations have been used for the evaluations of the unit cell parameters, bulk moduli, Debye temperatures. The values obtained are in good agreement with the experimental data. It is shown that h.c.p. WC has the highest bulk modulus, while W₂C possess the highest density-of-states at the Fermi level. The calculations reveal a noticeable charge transfer from tungsten to carbon in WC, while the effective charges in W₂C are rather small.     

Self-consistent LMTO approach to the electronic structure of semi-conductors: GaAs

The self-consistent Lineat Muffin Tin Orbital (LMTO) energy band method is applied to the case of the open structures (zinc blende) usual for many semi-conductors using GaAs as an example. Empty spheres are inserted into the most open parts of the structure and each sphere is assigned a spherically symmetric potential. The resulting band structure, density-of-state functions and XPS spectra (including matrix elements) are presented. Good agreement with more elaborate ab initio band results as well as with experiment is found. We conclude that the self-consistent LMTO approach using empty spheres provides a very efficient scheme for studying open structures.     

Self-consistent field electronic structure calculations for compressed magnesium oxide

Recently there have been reports that magnesium oxide and other ionic solids have been converted into metallic conductors when subjected to pressures of about 1 Mbar. Electronic structure calculations for compressed magnesium oxide indicate that the gap between valence and conduction bands does not close until much higher pressures are reached—perhaps around 50 Mbar.