First-Principles Calculation of Static Equation of State and Elastic Constants for GaSe

The all-electron full potential augmented plane-wave plus local orbital （APW_Io） method with the local-density approximation （LDA） is used to calculate the static equation of state （EOS） and elastic constants of crystalline GaSe. After the full relaxation of atomic positions, the calculated band structure at ambient pressure is consistent with the experimental data to the extent expected to give the known limits of LDA one-electron energies. The equilibrium lattice parameters found here exhibit the usual LDA-induced contraction. However, constrained with the experimental cell volume, the interlayer separation exhibits an expansion due to the LDA underestimate of the weak interlayer bonding. The calculated values of elastic constants are in good agreement with acoustic measurements. The pressure derivatives of the lattice constants derived from the theoretical elastic constants are in very good agreement with x-ray spectra measurements. Two analytical EOSs have been determined at pressures up to 4.5 GPa. The pressure evolution of the structure indicates that the layer thickness decreases slightly under pressure.     

Influence of Density-Dependent Coupling Constants on Equation of State of Infinite Symmetric Nuclear Matter

In the mean field approximation of nonlinear relativistic σ-ω-ρ model, we have studied the influence of density-dependent coupling constants between nucleons and mesons on the equation of state (EOS) of infinite symmetric nuclear matter in different conditions. We find that the EOS of nuclear matter will become stiffer as c, d in the self-interaction of σ meson increase when the coefficients except a_ω in Γ_ω, in which the opposite occurs, are fixed. On the other hand, greater values of a_σ, b_σ, c_σ, a_ω, d_ω and smaller values of d_σ, b_ω, c_ω will lead to stiffer EOS if c and d are fixed. Besides, greater values of Γ _σ,ω lead to stiffer EOS in high density region for the EOS with same incompressibility coefficient at saturation density.     

BGO晶体的布里渊散射与弹性系数测量

ＢＧＯ晶体的布里渊散射与弹性系数测量刘金全＊陈浩＊刘玉龙（中国科学院物理研究所北京１０００８０）（＊北京大学北京１００８７１）肖季驹（香港城市大学物理及材料科学系）ＥｌａｓｔｉｃＣｏｎｓｔａｎｔｓｏｆＢＧＯｂｙＢｒｉｌｏｕｉｎＳｃａｎｔｅｒｉｎｇＬｉ...     

Equation of State for Shock Compressed Xenon in the Ionization Regime:ab Initio Study

Quantum molecular dynamic (QMD) simulations have been applied to study the thermophysical properties of liquid xenon under dynamic compressions. The equation of state (EOS) obtained from QMD calculations are corrected according to Saha equation, and contributions from atomic ionization, which are of predominance in determining the EOS at high temperature and pressure, are considered. For the pressures below 160 GPa, the necessity in accounting for the atomic ionization has been demonstrated by the Hugoniot curve, which shows excellent agreement with previous experimental measurements, and three levels of ionization have been proved to be sufficient at this stage.     

Equation of State for Shock Compressed Xenon in the Ionization Regime: ab Initio Study

Quantum molecular dynamic (QMD) simulations have been applied to study the thermophysical properties of liquid xenon under dynamic compressions. The equation of state (EOS) obtained from QMD calculations are corrected according to Saha equation, and contributions from atomic ionization, which are of predominance in determining the EOS at high temperature and pressure, are considered. For the pressures below 160 GPa, the necessity in accounting for the atomic ionization has been demonstrated by the Hugoniot curve, which shows excellent agreement with previous experimental measurements, and three levels of ionization have been proved to be sufficient at this stage.     

高压下铜的声子谱和弹性系数

 以Foiles、Baskes和Daw提出的嵌入原子势（EAM）为基础,并结合Vinet-Rose形式的普适物态方程,建立了金属铜原子间的EAM势。在此基础上,用EAM势和第一原理微扰理论方法计算了高压下铜的声子谱和弹性系数。通过适当地调整嵌入原子势参数,这两种方法几乎能够给出完全一致的结果。而且,晶格振动声子谱和比热的理论值与实验值符合得也非常好。     

Master Equation and Fokker–Planck Equation: Comparison of Entropy and of Rate Constants

A usual approximation of the master equation is provided by the Fokker–Planck equation. For chemical systems with one species, we prove generally that the prediction of the rate constant of the metastable state given by the Master equation and the Fokker–Planck approximation differ exponentially with respect to the size of the system. We show that this is related to the fact that the entropy of the metastable state is not described correctly by the Fokker–Planck equation. We prove that the rate given by the Fokker–Planck equation overestimates that rate given by the Master equation.     

Elastic Constants of NaC1 under Pressure via First-Principles Calculations

The elastic constants of the B1 structure NaCl under pressure are obtained by using the ab initio plane-wave pseudopotential density functional theory method. The obtained zero pressure lattice constant and elastic constants are in good agreement with the available experimental data. It is found that the elastic constants C11 and C12 and the bulk modulus B increase monotonically with pressure P, however C44 increases monotonically when P_〈28 GPa and decreases when P〉28 GPa. Moreover, we discuss the B1-B2 structure phase transition of NaCl and obtain the transition pressure of 28.3 GPa.     

Epitaxial growth of fcc Fe on Cu(100)

Layer-by-layer epitaxial growth of Fe on Cu(100) is reported. The epitaxy is characterized using Auger electron spectroscopy and low energy electron diffraction intensity analysis. Good quality epitaxial Fe films having thicknesses ranging from one to four monolayers are stabilized by the Cu(100) substrate. The overlayer structure is shown to be nearly identical to a continuation of the fcc lattice of the substrate.     

Equation of state and thermodynamics of fcc transition metals: A pseudopotential approach

A simple pseudopotential model is used for the calculation of the phonon spectra at the equilibrium volume and under pressure. The model is based on the secondorder perturbation theory with the local pseudopotential acting on thes electrons while thed electrons contribution is simulated by the repulsive Born-Mayer interatomic potential. Pressure influence on the lattice properties was studied for small compressions (mode Grüneisen parameters) as well as for ultrahigh pressure (equation of state up to 1 TPa). Results of the lattice dynamics calculations were used for determining temperature dependence of the lattice heat capacity and of the macroscopic Grüneisen parameter. The Kohn anomaly at the small wave vectors obtained previously in palladium, platinum and rhodium affects strongly the temperature dependence at low temperature.     

最优化方法在拟合正交系晶体弹性及压电系数中的应用

由布里渊散射实验可以得到晶体弹性及压电系数。本文介绍了最优化方法在拟合正交晶体弹性及压电系数中的应用 ,并对几种主要的最优化算法的稳定性、初值选取、拟合数据结果的判断及评价等关键问题做了详细的讨论     

Ab Initio Calculations of Elastic Constants of Li2O under Pressure

We investigate the equilibrium lattice constant, bulk modulus, elastic constants and Debye temperature of Li2O under pressure by using ab initio unrestricted Hartree-Fock （HF） linear combination of atomic orbital （LCAO） periodic approach. The obtained results at zero pressure are well consistent with the available experimental data and other theoretical results, It is found that the elastic constants C11, C12 and C44 and bulk modulus B increase monotonously as pressure increases. Also, the anisotropy will weaken and the Debye temperature will rise with pressure increasing.     

原子核状态方程

介绍了在核子自由度占优势时原子核状态方程的一些知识,并对在饱和状态下直接研究和在重离子碰撞中间接研究原子核状态方程的情况做了评述． The knowledge of nuclear equation of state for which nucleonic effects are dominant is presented. The direct studies which close to the saturation state and the indirect studies involving heavy ion collisions on nuclear equation of state are reviewed.     

贵金属金的状态方程

 提出了一个热压强的计算公式,从而获得金的状态方程。并结合实验数据与文献中常用的其它两个状态方程进行了比较。结果发现,修正后的状态方程与实验数据吻合很好,略优于其它两个状态方程。