High pressure equation of state studies using methanol-ethanol-water and argon as pressure media

We have measured the equation of state of the intermetallic compound AuIn₂ up to 20 GPa and Cd_0.8Hg_0.2 up to 50 GPa using methanol-ethanol-water solution or argon as pressure media. In the experiments performed with argon as pressure medium, we minimized non-hydrostatic conditions by thermally annealing the sample. We present data revealing compressibility anomalies in AuIn₂ at 2.7 GPa and in Cd_0.8Hg_0.2 near 8, 18 and 34 GPa with methanol-ethanol-water and argon. At pressures above 5 GPa the P-V data for AuIn₂ and Cd_0.8Hg_0.2 from experiments preformed with argon as a pressure medium start deviating from those using methanol-ethanol-water, and the equation of state based on experiments in argon is stiffer compared with that in methanol-ethanol-water. This behavior is consistent with the relative merits of the two pressure transmitting media as documented in the literature. We also provide a brief summary of the results of electronic structure calculations that associate these anomalies with electronic topological transitions.     

高温高压下液态铁的状态方程

基于高温高压下面心立方(FCC)铁的状态方程和熔化温度实验数据,建立了热力学模型计算FCC铁、固-液混合相、液态铁在高温高压下的状态方程.在相同密度和温度下,计算的FCC铁、固-液混合铁、液态铁的压强与实验测量结果较为一致,且计算结果与实验结果平均偏差分别为-1.61 GPa、1.05 GPa、-0.05 GPa.在0～100 GPa压强范围内,当铁完全发生熔化时,随着压强的增大其密度变化由-7.5%下降至2.7%.     

Test of a high pressure equation of state

An equation of state for shock compressed matter is used to correlate P.V.T. data for Ag, Cu, Mo, Pd and K in the range from 0.05 to 0.95 M bar. Isotherms at 293K are obtained and the results are compared with static experimental data. Very good agreement between calculated and experimental values is generally obtained for all the materials considered. A critical analysis of the data is presented.     

一种激光驱动高压状态方程绝对测量方法的探索

数值模拟了激光直接驱动铝飞片空腔靶的物理过程,模拟结果表明,如果靶结构参数与激光条件匹配,飞片与靶可以近似实现对称碰撞,而且冲击波在靶中存在稳定传播区,采用结构参数合理的飞片双面台阶靶,可能实现状态方程的绝对测量.同时进行了实验探索,实验结果与数值模拟结果基本吻合. 关键词： 绝对测量 飞片双面台阶靶 数值模拟 状态方程     

Properties of solid argon under pressure

By using an improved nonsymmetric approximation of a self-consistent field for strongly anharmonic crystals and taking account of the anharmony to the sixth order, thermodynamic properties of solid argon were calculated in broad limits of the external parameters. Both the multiparametric pairwise potential of Barker and co-workers, and the 126 model potential of Lennard-Jones were used. The three-particle Axelrod-Teller-Muto forces were taken into account. A simple temperature dependence is obtained for the pressure and the isothermal elastic modulus. The results of the computations are compared with experimental data. The best agreement is assured by the Barker-Bobetic potential, while the Barker-Fisher-Watts potential leads to close results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 3, pp. 62–67, March, 1979.     

The Lindemann melting parameter for argon at high pressure

Elastic constant measurements in solidified argon near the melting temperature have been made for reduced volumes corresponding to melting temperatures from 123 to 206 K. Derived values of the Debye temperature in the limit T → T_m, allowed the Lindemann parameter to be determined, showing that within experimental error, the parameter is constant along that portion of the melting line.     

A molecular dynamical study of the equation of state of solids at high temperature and pressure

The molecular dynamics method of computer simulation was used to study the pressure and energy as a function of volume and temperature for f.c.c. neon with 6–12 Lennard-Jones interatomic forces and for b.c.c. iron with Morse interatomic forces. A self-consistent cell model was used to derive analytical formulae which describe the results of the computer experiments. A method for correcting the inherently classical results of the molecular dynamics calculations for the effect of quantum statistics is proposed. The results of the calculations are compared with experimental data and with various approximate methods for calculating the Grüneisen constant.     

Prototype of an LJ solid equation of state applied to argon,krypton and methane

A prototype of an equation of state for Lennard-Jones solids is developed on the basis of modified Weeks-Chandler-Andersen perturbation theory. This prototype is found to represent the melting pressures and molar volumes of solid argon, krypton and methane.     

高温高密度氩物态方程研究

用Exp-6有效两体势模型和液体变分微扰理论计算了液Ar冲击压缩曲线,在35 GPa以下的压力范围内计算的冲击压缩曲线与Thiel 及Nellis等人的实验数据进行了比较.液体分子间Exp-6有效两体势参数根据实验数据计算优选出最佳值,计算结果表明得到的优选参数较为准确地描述了液Ar分子间相互作用.由理论结合实验数据可以认为液氩体系在冲击压力36 GPa以下无相变现象.对较高冲击压力下理论计算的冲击曲线和实验结果之间的偏差作了分析,结合不透明度实验的结果,得到当压力超过35 GPa,温度在12 000 K     

高密度氩气的原子间相互作用与状态方程

本文从高密度气体的原子间相互作用出发进行思考,在修改范德瓦耳方程的基础上,提出了一种新的适用于高密度气体的状态方程,并用以对氩气临界区的等温压缩线进行计算,结果与实验值很符合.     

用Hugoniot数据计算高压状态方程

提出了利用Hugoniot数据、变形Morse势和Grüneisen模型来确定固体材料的高压状态方程的方法。该方法物理意义明确,表达式简洁。用此方法计算Au的高压状态方程,将所得的状态方程与Sesame数据库中Au的状态方程进行比较,发现在密度20~28 g/cm3内两者吻合较好,相对误差在0~10%的范围内,表明运用Hugoniot数据结合Grüneisen模型计算材料的状态方程是很适合的。     

Supernovae and the nuclear equation of state at high densities

An extensive study of the shock-explosive mechanism for generating type II supernovae is made. The nuclear high-density equation of state plays an important role, moderate softening of the equation of state leading to a considerable increase in shock strength. A definition of shock energy which can be used throughout the life of the shock is introduced.     

固态氩弹性性质的量子力学从头计算

本文从量子力学第一性原理出发,用平面波赝势 (PWP)结合广义梯度近似(GGA)密度泛函理论方法,计算了零温下固态氩晶体0～82 GPa压力范围内的弹性性质,体系电子-离子相互作用采用硬赝势描述.计算结果与静高压实验数据良好相符,通过计算表明采取合理的方法和计算参数,惰性气体固态晶体高压下的力学性质可以比较准确地计算出来,这可为实验上难于进行研究的物质提供有意义的参考.     

A stationary filamentary microwave discharge at a high pressure of argon

A stationary discharge in the form of a filament about 1 mm in diameter is produced in a quartz tube 16 mm in diameter passed through the wider wall of a standard waveguide and field with argon at a pressure of 300 mm Hg at a microwave power of 50 W on a frequency of 7 GHz. The number of filaments increases gradually from one to seven as the power and pressure are increased. The filaments are parallel and oriented along the electric field of the wave. They are arranged symmetrically relative to the equatorial plane of the tube. The distance between the filaments decreases as their number increases. The stationary filaments arising due to ionization-overheating instability may be explained qualitatively using the interference-equilibrium model and assuming that a discharge is organized such as to provide for the maximal power absorption.     

Simulated equation of state of CaF2 with fluorite-type structure at high temperature and high pressure

The pressure-volume-temperature (P-V-T) equation of state (EOS), isothermal bulk modulus, and thermal expansivity of CaF₂ with cubic fluorite-type structure are investigated using the constant temperature and pressure shell model molecular dynamics (MD) method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It was shown that MD simulation is very successful in accurately reproducing the measured volumes of the CaF₂ over a wide range of pressures. The simulated P-V data matched X-ray diffraction experimental results up to 9.5 GPa at 300 K. In addition, volume thermal-expansion coefficient and isothermal bulk modulus were also calculated and compared with available experimental data and the latest theoretical results at ambient condition. At extended temperature and pressure ranges, The P-V EOS under different isotherms at selected temperatures, T-V EOS under different isobars at selected pressures, thermal expansivity, and isothermal bulk modulus were predicted up to 1500 K and 10 GPa. The detailed knowledge of thermodynamic behavior and EOS at extreme conditions are of fundamental importance to the understanding of the physical properties of CaF₂.     

Potentialities for solid state maser excitation by dynamic high pressure

During rapid transitions of solid state quantum systems between different high pressure equilibrium states, deviations from thermodynamical equilibrium, like in an excited maser system, are presumed.     

The first-principle study on the equation of state of HMX under high pressure

The equation of states (EOS) of high energy explosive HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) has been studied by using the first principle method. Our results include the lattice constants, elastic constants, and the dependence of total energy and pressure on volume for βand δ-HMX. The calculated elastic constants and the pressure-volume relationship of β-HMX are also compared with the experimental values. The theoretical tensile experiments are implemented on the β-HMX. The atomic-scale ana...