Quantum-mechanical calculations based on density functional theory

The basic concepts of density functional theory (DFT) together with the local density approximation (LDA) and the recent improvement in form of the generalized gradient approximations (GGA) are discussed. Band structure calculations using the full-potential linearized augmented plane wave (FP-LAPW) method are presented in relation to pseudopotential schemes both corresponding to T=0. For finite temperatures the most advanced technique is the Car-Parrinello (CP) molecular dynamics (MD) approach, e.g. in its projector augmented wave (PAW) implementation. In CP-MD simulations nuclear motion and the electronic degrees of freedom are treated within one formalism. Such DFT calculations are illustrated for selected examples, including the breathing mode of BaBiO₃. the phase transition in SrTiO₃ and VO₂ and the Li diffusion in the superionic conductor Li₃N studied by conventional and CP molecular dynamics.     

First-principles study of the structural,mechanical and electronic properties of ZnX2O4（X=Al,Cr and Ga）

This paper performs first-principles calculations to study the structural,mechanical and electronic properties of the spinels ZnAl2O4 ,ZnGa2O4 and ZnCr2O4 ,using density functional theory with the plane-wave pseudopotential method. Our calculations are in good agreement with previous theoretical calculations and the available experimental data. The studies in this paper focus on the evolution of the mechanical properties of ZnAl2O4 ,ZnGa2O4 and ZnCr2O4 under hydrostatic pressure. The results show that the cubic phases of ZnAl2O4 ,ZnGa2O4 and ZnCr2O4 become unstable at about 50 GPa,40 GPa and 25 GPa,respectively. From analysis of the band structure of the three compounds at equilibrium volume,it obtains a direct band gap of 4.35 eV for ZnAl2O4 and 0.89 eV for ZnCr2O4 ,while ZnGa2O4 has an indirect band gap of 2.73 eV.     

高压下TiN等结构相变的第一性原理研究

 利用基于密度泛函理论的赝势平面波方法和线性响应理论,研究了TiN的物态方程、电子能带结构和声子色散曲线随压强的变化关系。结果表明：TiN 的电子能带结构并未随着压强的增加而出现反常,没有出现电子的拓扑结构相变;零压下出现软化的声子模式并没有随着压强的增加而继续软化。因此可以认为在0～12 GPa 压强范围内,TiN 发生等结构相变的原因不是由于电子的拓扑形貌发生变化和声子软化引起的。     

The electronic structure and superconductivity of tellurium at high pressure

Abstract

The electronic bandstructure of tellurium performed at 33 GPa, the highest pressure up to which experimental structural information is available and also its superconducting behaviour are reported here. The bandstructure calculation is done using the self-consistent Linear Muffin Tin Orbital (LMTO) method. The calculation shows a large d density of states at the Fermi energy even though this is a sp metal. The usual s → d transfer mechanism is found to be responsible for the pressure induced superconductivity. The calculated value of T_c agrees fairly well with the experimental value.     

First-principles study of the structural,mechanical and electronic properties of ZnX204 （X=Al,Cr and Ga）

This paper performs first-principles calculations to study the structural, mechanical and electronic properties of the spinels ZnA1204, ZnGa2O4 and ZnCr2O4, using density functional theory with the plane-wave pseudopotential method. Our calculations are in good agreement with previous theoretical calculations and the available experimental data. The studies in this paper focus on the evolution of the mechanical properties of ZnAl2O4, ZnGa2O4 and ZnCr2O4 under hydrostatic pressure. The results show that the cubic phases of ZnAl2O4, ZnCa2O4 and ZnCr2O4 become unstable at about 50 GPa, 40 GPa and 25 GPa, respectively. From analysis of the band structure of the three compounds at equilibrium volume, it obtains a direct band gap of 4.35 eV for ZnA1204 and 0.89 cV for ZnCr2O4, while ZnGa2O4 has an indirect band gap of 2.73 eV.