一种新的对比态混合物状态方程的建立

1引言在混合替代工质的研究中，要分析其热力学性质和循环性能，必须有能够准确描述混合制冷剂性质的状态方程。目前计算采用的各种混合状态方程都必需有混合物各组分间的二元交互作用系数Kij。Kij的值一般需要由回归二元混合工质的PVTx实验数据或相平衡数据而得到。实际的混合工质替代研究中，常常没有或缺少混合物的实验数据。对于二元混合物而言，其热力性质应与组成这种混合物的两种纯质的性质密切相关，有可能以纯质的物性来表达混合物的性能，而大多数纯质制冷剂都有用实验数据回归的精度很高的专用状态方程和蒸气压方程。所以，如…     

两种状态方程参数的计算

在一定程度上,状态方程的形式与外推数据的置信度有直接影响,对于在高压下发生反应的材料,通过外推方式计算其未反应状态具有一定的意义。依据由Vinet以及Parsafar和Mason(简称P-M)等人提出的两种统一状态方程,对以其为等温压缩线的完全状态方程进行了研究。根据对热力学状态量的分析,从热压系数和定容比热入手,对完全状态方程的建立进行了讨论,给出了在已知物质等温线条件下构成状态方程的方法,并推导了Vinet和P-M两种表达式的完全状态方程形式。以几种材料为例,通过实验测量的冲击绝热线和有关参数,采用最小二乘法,对其状态方程进行了拟合。结果表明,由冲击绝热线拟合的状态方程与实验结果相吻合。     

CdTe的状态方程及其高压相变

 用金刚石压砧高压X光衍射技术研究了Ⅱ-Ⅵ族化合物CdTe的室温状态方程和室温高压相变。实验的最高压力达39.2 GPa。实验中发现CdTe从(3.3±0.1)GPa开始从闪锌矿结构相相NaCl结构相转变，相变时体积收缩15.8%；从(10.3±0.2)GPa开始从NaCl相向β-Sn结构相转变，相变时无体积突变；在(12.2±0.2)GPa由β-Sn相向正交结构相转变，相变时也无体积突变。CdTe的压缩数据用最小二乘法以Bridgman状态方程和Murnaghan状态方程拟合，得到其零压时合相变压力时各个相的体弹模量及体弹模量的压力微商，并与其它的实验合理论结果进行比较。     

激光直接驱动状态方程实验铝铜阻抗匹配靶的制作和测量

阻抗匹配法是激光状态方程实验重要的测量方法，阻抗匹配靶的质量与靶参数的测量精度直接影响状态方程实验数据的可靠性与精度。因此，2004年致力于高质量铝铜阻抗匹配靶的制作，并努力提高靶参数的测量精度。     

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。     

激光驱动高压下材料状态方程实验研究进展

利用激光驱动冲击波进行材料状态方程实验研究已逐渐成为实验室获得材料TPa以上高压状态方程数据的重要途径.文章简述了激光状态方程实验研究方面的进展,重点介绍了激光驱动冲击波的基本特性,激光状态方程实验测量方法,激光驱动冲击波平面性、稳定性及干净性研究,以及激光状态方程实验研究等方面的成果.     

论VLW状态方程

 论述了VLW状态方程中爆轰产物分子势参数的确定；根据不同类型炸药爆轰性能参数计算结果对炸药爆轰产物碳在CJ态的相进行了分析讨论，认为不同的炸药，产物碳有石墨和金刚石两种相存在；将VLW状态方程和BKW状态方程进行了比较分析，指出了BKW状态方程与VLW状态方程的区别及其产生的原因，并给出了VLW状态方程计算含能材料（包括高能炸药、燃料空气炸药、民用炸药）的爆轰性能参数计算结果。结果表明，计算值与实验值符合较好。     

固体氢的压缩行为

 同时考虑分子的平动与转动自由度，用等温等压系综的路径积分蒙特卡罗方法研究了固体氢的状态方程。在有实验数据的区域，计算结果同实验结果符合很好，在无实验数据的超高压区域，计算结果同实验的外推结果符合。为了定量研究零点运动，还计算了体系的能量。     

炸药爆轰产物Jones-Wilkins-Lee状态方程不确定参数

Jones-Wilkins-Lee (JWL)状态方程是一种不显含化学反应、由实验方法确定参数的半经验状态方程, 能比较精确地描述爆轰产物的膨胀驱动做功过程. 在JWL状态方程中有多个未知(不确定)参数需要确定. 传统的确定JWL状态方程参数的方法是“调参数”, 人为因素影响较大, 无法给出参数的不确定性信息. 本文利用贝叶斯分析方法研究了炸药的不确定参数, 该方法能够基于以往的认识、实验和模拟数据标定(calibration)不确定参数. 在本文结果中, 不确定参数的后验分布均值与文献结果相符合, 基于参数标定结果的数值模拟90%置信区间完全包含实验数据. 数值标定结果说明贝叶斯参数标定适用于确定样品炸药的JWL状态方程参数. 特别是, 在本文JWL状态方程参数标定过程中极大地减少了人为因素的影响.     

激光状态方程实验数据在线处理程序的开发及应用

 主要介绍一套用于提高激光状态方程实验数据处理效率的程序，该数据处理程序减少了手工处理方法引入的人为因素的影响，减小了随机误差，大大提高了数据处理效率，并可以实现实验数据的在线处理。     

纳米结构泡沫金冲击响应的分子动力学模拟

采用分子动力学计算程序对纳米结构泡沫金(Au)的冲击响应进行了模拟,得到了不同疏松度条件下泡沫Au的冲击压缩特性。通过获取不同势函数条件下实密Au的冲击Hugoniot关系以及泡沫结构稳定性测试选取适合描述Au泡沫冲击过程中原子的相互作用势。采用密堆积球壳的方式建立泡沫Au的初始构型。通过改变空心球壳的尺寸得到不同疏松度的稳定的泡沫Au结构。对泡沫Au的冲击过程进行分子动力学模拟,获得了不同疏松度泡沫Au在不同冲击压缩强度下的热力学状态参数。将模拟结果与已有的状态方程数据库以及疏松物质冲击压缩模型进行比较,结果表明,计算和理论模型给出的结果仍然存在明显的差异性,亟需通过进一步实验研究来验证模拟计算和理论模型结果的可靠性。     

Enhanced KR-Fundamental Measure Functional for Inhomogeneous Binary and Ternary Hard Sphere Mixtures

An enhanced KR-fundamental measure functional (FMF) is elaborated andemployed to investigate binary and ternary hard sphere fluids near a planarhard wall or confined within two planar hard walls separated by certaininterval. The present enhanced KR-FMF incorporates respectively, for aim ofcomparison, a recent 3rd-order expansion equation of state (EOS) and aBoublik's extension of Kolafa's EOS for HS mixtures. It is indicated that the two versions of the EOS lead to, in the framework of the enhanced KR-FMF, similar density profiles, but the 3rd-order EOS is more consistent with an exact scaled particle theory (SPT) relation than the BK EOS. Extensive comparison between the enhanced KR-FMF-3rd-order EOS predictionsand corresponding density profiles produced in different periods indicatesthe excellent performance of the present enhanced KR-FMF-3rd-order EOS incomparison with other available density functional approximations (DFAs).There are two anomalous situations from whose density profiles all DFAsstudied deviate significantly; however, subsequent new computer simulationresults for state conditions similar to the two anomalous situations are invery excellent agreement with the present enhanced KR-FMF-3rd-order EOS. The present paper indicates that (i) the validity of the ``naive' substitutionelaborated in the present paper and peculiar to the original KR-FMF is stillin operation even if inhomogeneous mixtures are being dealt with; (ii) thehigh accuracy and self-consistency of the third order EOS seem to allow forapplication of the KR-FMF-third order EOS to more severe state conditions;and (iii) the ``naive' substitution enables very easy the combination of theoriginal KR-FMF with future's more accurate but potentially more complicatedEOS of hard sphere mixtures.     

Analysis of K-prime equations of state

We present an analysis of the $K$-prime equations of state (EOS) due to Keane and Stacey. It is found that the two EOS differ significantly from each other in some important respects. $K$-prime represents the pressure derivative of the bulk modulus. It is shown that the volume dependence of $K$-prime and higher derivative properties predicted from the Keane EOS are compatible with those predicted from Stacey’s reciprocal $K$-prime EOS only when the Murnaghan approximation is valid. It has been emphasized that the Stacey EOS is more appropriate for describing the relationship between pressure and the bulk modulus and its pressure derivative. The results based on the two EOS have been compared and discussed.     

Two universal equations of state for solids satisfying the limiting condition at high pressure

In this paper it is shown that the relationship of bulk modulus with pressure, B=f(P), should be linear both at low and high-pressure limiting conditions. Because most of present equations of state (EOS) for solids cannot satisfy such linear relationship at high pressure, a new function f(P) is proposed to satisfy the linearity. By integrating the bulk modulus, an EOS with three parameters and satisfying the quantum-statistics limitation is derived. It is shown that the EOS can be reduced to two-parameter EOS approximately satisfying the limiting condition. By applying the two EOSs and other three typical EOSs to 50 materials, it is concluded that for materials at low and middle-pressure regimes, the limiting condition does not operate, the Baonza EOS gives the best results, but it cannot provide analytic expression for cohesive energy. The Vinet and our second EOSs are slightly inferior, both EOSs can provide analytic expression for cohesive energy, and for materials at high-pressure regimes our second EOS gives the best results. The Holzapfel and our first EOSs give the worst results, although they strictly satisfy the limiting condition. For practical applications, the limiting condition is not important because it only operates as V→0.     

Equations of state for strong compression

Abstract

Various higher order equations of state (EOS) are compared with theoretical predictions for strong compression as well as with different linearization schemes. One specially convenient EOS together with a conjugated linearization scheme is presented as a series expansions with the appropriate asymptotic behaviour at very strong compression. Tests for the uncertainties in EOS extrapolations are discussed. A comparison with literature data for highly compressible solids illustrates the advantages of the present EOS with respect to many other commonly used forms.     

Equation of state of hydrogen,helium, and solar plasmas

The equation of state (EOS) for plasmas of the two lightest elements H and He, and mixtures as typical for the plasmas in the sun are calculated. The contributions of deep bound states are included by using inverted fugacity expansions. The inversion of fugacities to densities is reduced to solvable algebraic problems and expressed by rational polynomials. The calculation of relative pressures is carried out separately for low and high densities. Near the crossing point, in between, the separate solutions are connected to each other by smooth concatenation. Applications to hydrogen–helium plasmas in the sun including estimates for the isentropic EOS are discussed.     

Equation of state and P-V-T properties of polymer melts based on glass transition data

This paper addresses a method for predicting the participating constants in equation of state (EOS) for compressed polymeric fluids using two scaling constants. The theoretical EOS undertaken is Ihm-Song-Mason (ISM), which is based on the Weeks-Chandler-Anderson (WCA), and the two constants are the surface tension γ_g and the molar density ρ_g, both at the glass transition point. There are three temperature-dependent quantities that are required to use the EOS: the second virial coefficients B₂(T), an effective van der Waals co-volume, b(T) and a correction factor, α(T). The second virial coefficients are calculated from a two-parameter corresponding states correlation, which is constructed with two constants as scaling parameters, i.e., the surface tension γ_g and molar density ρ_g. This new correlation has been applied to the ISM EOS to predict the volumetric behavior of polymer melts including polypropylene (PP), poly(ethylene oxide) (PEO), polystyrene (PS), poly(vinyl methyl ether) (PVME), and polycarbonate bisphenol-A (PC) at compressed states. The operating temperature range is from 311.5 to 603.4 K and pressures up to 200.0 MPa. Other two-temperature-dependent parameters α(T) and b(T) appearing in the ISM EOS, are calculated by scaling rules. It was found that the calculated volumes agree well with the experimental values. A collection of 421 data points has been examined for the aforementioned polymers. The average absolute deviation between the calculated densities and the experimental densities is of the order of 0.6%. The newly obtained correlation has been further assessed through a detailed comparison against previous correlations proposed by other researchers.     

Extension of Compressibility-Route Cubic Equations of State and the Radial Distribution Functions at Contact to Multi-Component Hard-Sphere Mixtures

The equation of state (EOS) for hard-sphere fluid derived from compressibility routes of Percus-Yevick theory (PYC) is extended. The two parameters are determined by fitting well-known virial coefficients of pure fluid. The extended cubic EOS can be directly extended to multi-component mixtures, merely demanding the EOS of mixtures also is cubic and combining two physical conditions for the radial distribution functions at contact (RDFC) of mixtures. The calculated virial coefficients of pure fluid and predicted compressibility factors and RDFC for both pure fluid and mixtures are excellent as compared with the simulation data. The values of RDFC for mixtures with extremely large size ratio 10 are far better than the BGHLL expressions in literature.     

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.     

Extension of Compressibility-Route Cubic Equations of State and the Radial Distribution Functions at Contact to Multi-Component Hard-Sphere Mixtures

The equation of state(EOS) for hard-sphere fluid derived from compressibility routes of Percus-Yevick theory(PYC) is extended. The two parameters are determined by fitting well-known virial coefficients of pure fluid.The extended cubic EOS can be directly extended to multi-component mixtures, merely demanding the EOS of mixtures also is cubic and combining two physical conditions for the radial distribution functions at contact(RDFC) of mixtures.The calculated virial coefficients of pure fluid and predicted compressibility factors and RDFC for both pure fluid and mixtures are excellent as compared with the simulation data. The values of RDFC for mixtures with extremely large size ratio 10 are far better than the BGHLL expressions in literature.