液氩冲击压缩特性的理论计算

用修正的WCA状态方程和Ross变分微扰理论计算了液氩冲击压缩曲线,计算中体系分子间相互作用势选择EXP-6有效两体势模型,计算结果与Nellis等人的实验数据符合较好.     

用指数参考势计算水的冲击压缩Hugoniot曲线和温度

 在修正的WCA状态方程和Ross变分微扰理论的基础上，计算了水的exp-6参考势对应的硬球直径、相应的λ值及冲击Hugoniot曲线和温度。将理论结果与实验结果进行了比较，我们计算的冲击Hugoniot曲线和温度与实验符合较好。     

液氩冲击压缩特性的理论计算

用修正的WCA状态方程和Ross变分微扰理论计算了液氩冲击压缩曲线，计算中体系分子间相互作用势选择EXP-6有效两体势模型，计算结果与Nellis等人的实验数据符合较好。     

炸药爆轰产物液氮、液氦和水状态方程研究

 使用修正的WCA状态方程和Ross变分微扰理论研究了炸药爆轰产物（液氮、液氦和水）的冲击压缩特性,并利用exp-6形式的势函数计算分子间相互作用贡献的自由能。研究和计算经验表明,在研究高温高密度条件下液体的冲击压缩特性时,分子间多体相互作用十分重要,多体作用的结果是软化了两体相互作用势。     

液氮的冲击压缩理论计算

 使用修正的WCA状态方程研究液氮的冲击压缩特性，并利用exp-6形式的势函数、用Ross变分微扰理论计算分子间相互作用贡献的自由能。计算的液氮冲击压缩Hugoniot曲线与实验数据符合较好。     

高温高压下爆轰产物分子间相互作用的研究

给出了一种由分子流体的冲击Hugoniot实验数据确定原分子之间和离解产物分子、原子相互间作用势参数的方法. 在较低压强下,采用Ross硬球微扰理论软球修正模型确定原分子之间的相互作用势参数;在较高压强下,采用基于统计物理的化学平衡方法来确定分子离解后的分子和原子之间的相互作用势参数. 与传统的由对应状态定律确定势函数参数的方法相比,所得到的势函数参数在很大的压强范围内都能较好地描述冲击实验. 关键词： 高温高压 化学平衡 冲击Hugoniot实验     

PETN炸药爆轰产物状态方程的理论研究

 采用van der Waals等效单组分流体模型和Ross硬球微扰理论软球修正模型,计算爆轰气相产物的状态方程;用石墨相、金刚石相、类石墨液相和类金刚石液相4种相态描述凝聚成分,由Gibbs自由能最小原理确定不同状态下的凝聚产物相态。对爆轰产物混合系统采用自由能最小原理,通过化学平衡方程组求解炸药爆轰产物系统的平衡组分。使用该理论计算PETN炸药Chapman-Jouguet（CJ）点的爆轰参数,其值与实验值符合得很好;同时计算了以CJ点为起始点的等熵卸载线,并与传统的Jones-Wilkins-Lee（JWL）状态方程的计算结果进行比较,发现计算的γ值是单调递减的,而JWL状态方程计算的γ值却出现了“双峰”现象。分析认为,传统的JWL状态方程给出的“双峰”变化,是由其函数形式自身决定的,并不对应实际物理过程。     

高温高密度氢（氘）的物态方程——离解效应研究

 高温高压下流体氢将发生离解化学反应，形成具有相互作用的氢分子和氢原子混合体系，此时粒子间的相互作用复杂。利用单组分流体近似的范德瓦尔斯混合模型，将混合物粒子间的相互作用等效为单组分粒子间相互作用，从而简化了对体系的统计热力学处理；并由自由能函数极小化确定化学平衡时各组分含量、体系的内能、压强。研究了温度在10 000 K以下、密度在0.6 g/cm³以下（相应摩尔体积大于3.3 cm³/mol）区间的热致离解和压致离解现象对流体氢（氘）状态方程的影响。所得结果与双组分流体变分理论计算以及第一原理的分子动力学模拟、蒙特卡罗模拟结果以及二级轻气炮实验数据进行了比较，它们之间的一致性表明：用单组分流体近似的范德瓦尔斯混合模型处理氢（氘）分子的离解区域的物态方程是成功的。     

氢化氙离子XeH+基态X1S+解析势能函数的变分研究

采用双原子分子离子XY+的能量自洽法(Energy-consistent -method for ion XY+, ECMI)研究了氢化氙离子XeH+基态X1S+的解析势能函数,并与解析形式的Morse势和Huxley- Murrell-Sorbie（HMS）势、耦合电子对方法(coupled electron pair approximation method, CEPA)的结果和基于实验的Rydberg-Klein-Ress（RKR）数据进行了比较。结果表明,由ECMI方法得到的解析势能函数ECMI势明显优于Morse势和HMS势,与理论方法的结果和RKR数据符合得很好,并能得到CEPA和RKR非法缺乏的离解区和渐近区的势能数据以及正确的离解极限,而正确的全程势能数据对研究各种散射问题都是非常必要的。     

氢化氙离子XeH+基态X1S+解析势能函数的变分研究

采用双原子分子离子XY+的能量自洽法(Energy-consistent -method for ion XY+, ECMI)研究了氢化氙离子XeH+基态X1S+的解析势能函数,并与解析形式的Morse势和Huxley- Murrell-Sorbie（HMS）势、耦合电子对方法(coupled electron pair approximation method, CEPA)的结果和基于实验的Rydberg-Klein-Ress（RKR）数据进行了比较。结果表明,由ECMI方法得到的解析势能函数ECMI势明显优于Morse势和HMS势,与理论方法的结果和RKR数据符合得很好,并能得到CEPA和RKR非法缺乏的离解区和渐近区的势能数据以及正确的离解极限,而正确的全程势能数据对研究各种散射问题都是非常必要的。     

Thermodynamic properties of cubic boron nitride based on an analytic mean field approach

We present a detailed derivation of the analytic expressions for the equation of state (EOS) and internal energy of Morse model solids based on an analytic mean field potential (AMFP) method. The formalism is applied to cubic boron nitride (c-BN). One set of potential parameters are determined by fitting the experimental P-V-T data of c-BN up to 160 GPa at 295 K and 80 GPa in the range 500–900 K. Various physical quantities including the isothermals, thermal expansion, isochoric heat capacity, Helmholtz free energy and internal energy are calculated and analyzed. The theoretical results are consistent with the available experimental data and those calculated by others. These results presented in this paper verify that the AMFP method is a useful approach to consider the anharmonic effect at high temperature. Numerous reasonable predictions and the change trend of the properties for c-BN at extreme conditions have been given.     

A modified equation of state for Xe at high pressures by molecular dynamics simulation

The exact equation of state （EOS） for the fission gas Xe is necessary for the accurate prediction of the fission gas behavior in uranium dioxide nuclear fuel, However, the comparison with the experimental data indicates that the applicable pressure ranges of existing EOS for Xe published in the literature cannot cover the overpressure of the rim fission gas bubble at the typical UO2 fuel pellet rim structure. Based on the interatomic potential of Xe, the pressure-volume-temperature data are calculated by the molecular dynamics （MD） simulation. The results indicate that the data of MD simulation with Ross and McMahan＇s potential [M. Ross and A. K. McMahan 1980 Phys. Rev. B 21 1658] are in good agreement with the experimental data. A preferable EOS for Xe is proposed based on the MD simulation. The comparison with the MD simulation data shows that the proposed EOS can be applied at pressures up to 550 MPa and 3 GPa and temperatures 900 K and 1373 K respectively. The applicable pressure range of this EOS is wider than those of the other existing EOS for Xe published in the literature.     

4种等温物态方程适用性的比较研究

 通过分析现有文献，认为4种两参数的物态方程在高压物理研究中较为流行，它们是Vinet、Baonza、Morse和Born-Meyer（BM）方程。将这4种方程用于拟合50种材料的实验压缩数据，得出了零压下压缩模量及其一阶压力导数的优化取值，并计算了4种方程的平均压力误差。结果表明，Morse方程的精度最高，对50种材料的平均拟合误差为0.557 6%；BM方程次之，平均误差为0.615 1%；Vinet和Baonza方程的误差大一些，分别为0.788 9%和0.833 3%。对8种典型材料计算了压力误差随压强变化的曲线，所得结果与平均误差的趋势一致，也是Morse方程的精度最高。在宽广压力范围的高压物态方程研究中，推荐使用Morse方程。     

Analytical equations of state for multi-Yukawa fluids based on the Ross variational perturbation theory and the Percus-Yevick radial distribution function of hard spheres

Analytical expressions for equation of state and thermodynamic properties have been derived for the multi-Yukawa fluids, based on the Ross variational perturbation theory and the analytical Percus–Yevick (PY) expression for the radial distribution function of hard spheres. It is shown that the variational procedure is absolutely convergent and the calculations are convenient and fast. By using the parameters fitted to the Lennard–Jones 12–6 potential from the literature, numerical calculations have been made within wide temperature and density ranges. Comparison with computer simulations shows that the precision of the analytical Ross theory based on the Yukawa-type potential is equivalent to the non-analytical Ross theory based on the Lennard–Jones 12–6 potential. It is concluded that the analytical theory based on the Yukawa-type potential can be applied to research practical fluids within wide temperature and density ranges.     

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.     

Experimental evidence for a high-pressure isostructural phase transition in osmium

We have measured the isothermal equation of state (EOS) of osmium to 75 GPa under hydrostatic conditions at room temperature using angle-dispersive x-ray diffraction. A least-squares fit of this data using a third-order Birch-Murnaghan EOS yields an isothermal bulk modulus K0=411+/-6 GPa, showing osmium is more compressible than diamond. Most importantly, we have documented an anomaly in the compressibility around 25 GPa associated with a discontinuity in the first pressure derivative of the c/a ratio. This discontinuity plausibly arises from the collapse of the small hole-ellipsoid in the Fermi surface near the L point.     

爆轰产物的冷比内能与冷压的函数表达式

 猛炸药爆轰产物的状态可以用两相的强排斥-平动物态方程（简称为两相的排平物态方程）很好地描述。以爆轰产物分两段的等熵曲线为参考曲线的两相的排平（k, γ）物态方程,已经用于爆轰参数和强爆轰参数的理论估算,所得理论值与实验值符合得很好。为了更方便地估算爆温,有必要给出描述分子间相互作用的比内能项与压力项（分别简称为冷比内能与冷压）。参照描述分子间相互作用的Morse势和Mie势的排斥项,给出了带待定参数A、m、n和l的冷比能项和冷压项,这样的物态方程被称为两相的排平（A, m, n, l）物态方程。用TNT的{D, ρ₀}实验数据组,确定了两相的排平（A, m, n, l）物态方程的参数n=1和l=1/3,因此,可将其简称为两相的排平（A, m）物态方程。它适用于所有的猛炸药的爆轰产物。用硝基甲烷的强爆轰参数{p, D, T}实验数据组对其所做的检验表明,两相的排平（A, m）物态方程是恰当的爆轰产物物态方程。     

Structural and Thermodynamic Properties of TiAl intermetallics under High Pressure

The structural and thermodynamic properties of TiAl intermetallics under high pressure have been investigated by ab initio plane-wave pseudopotential density functional theory method.It is found that the ratio of lattice parameter c to a keeps almost constant with a value of 1.02 under the pressure from 0 to 20 GPa,which agrees well with the experimental results.With the pressure increasing from 20 to 45 GPa the values of c/a decrease almost linearly from 1.02 to 0.99.These calculated results indicate under low pressure the variation rate for a-axis is almost the same to that for c-axis,but under higher pressure the variation for a-axis is smaller than along c-axis.Through the quasi-harmonic Debye model,the equation of state(EOS) of TiAl intermetallics,as well as the thermal expansion and heat capacity at various pressures and temperatures are also studied.     

高压下天然顽火辉石能量色散X射线粉末衍射研究

 在北京同步辐射装置（BSRF）高压站对采自于河北大麻坪的天然顽火辉石，在室温高压（0~31.64 GPa）下，利用金刚石压腔装置（DAC），进行了能量色散X射线粉末衍射（EDXD）原位测量，得到了顽火辉石在不同压力下的衍射图谱，并利用UnitCell软件进行解谱，获得了其晶胞参数a、b、c和晶胞体积V及其随压力的变化，最后利用Murnaghan等温方程得到了天然顽火辉石的体积模量K_T(0)=172 GPa、压缩系数及p-V状态方程，发现沿a、b、c三方向的压缩系数存在明显的各向异性，结果与斜方辉石的弹性波速各向异性完全一致。