利用乙醇音速计算其它热力学性质

光散射法音速测量的适用温度范围较广,且有时高温比定压热容相对于密度而言更容易获得实验数据.基于此,提出了一个由较高温度比定压热容推算得到较高温度密度的迭代算法.以乙醇为例,利用高温热力学性质推算模型得到298.15～418.15 K、1.0 MPa下乙醇的密度,与Schroeder状态方程的计算结果进行对比,二者的平均绝对相对偏差为0.0119％,最大偏差为0.0298％.此外,沿1.0 MPa等压线测量了298.45～423.02 K温度范围内乙醇的液相音速,测量的拓展相对不确定度为0.9％(置信因子取2).与Schroeder状态方程相比,298.15～418.15K、1.0～9.0 MPa下乙醇密度和比定压热容计算值的平均相对偏差分别为0.0072％和0.0067％,最大偏差分别为0.0298％和0.0290％.可以看出,高温热力学性质推算模型的密度计算精度与实验测量精度相当.     

从头算方法研究面心立方铝在高温高压下的热力学状态方程

用从头算方法优化计算了面心立方铝的电子结构和总能,得到了它在零温下的状态方程和弹性性质.将得到的总能与晶格体积拟合到Debye模型,获得了非平衡态下的Gibbs自由能与温度、压力之间的关系,在此基础上计算了相应的热状态方程,利用Burakovsky-Preston-Silbar （BPS） 熔化模型计算了铝的熔化曲线.所有的电子结构和总能计算都是基于局域密度近似（LDA）和广义梯度近似（GGA）的平均得到的.计算得到的铝在高温、高压下的状态方程与一些热力学性质和熔化曲线同冲击波和静高压实验数据在225 G 关键词： 铝 热力学状态方程 从头算 熔化曲线     

高温等离子体的状态方程及其热力学性质

高温下等离子体的状态方程及其热力学性质在天体物理、可控核聚变以及武器设计与破坏效应等领域有着广泛应用.本文主要回顾了高温等离子体在不同状态区域的状态方程的理论模型和处理方法.对于理想等离子体,离子之间的相互作用可以忽略,其状态方程较简单,已趋于完善.在超高温下,原子完全电离,离子和电子都可以采用理想气体状态方程描述;当温度不太高时,离子部分电离,可以采用Saha方程及其修正模型描述;原子在高度压缩状态下,其状态方程可以采用Thomas-Fermi模型及其改进模型得到.对于非理想等离子体,离子之间存在强耦合,还没有单一的理论模型能够在任意密度和温度范围内对离子之间的相互作用进行统一描述.量子分子动力学方法原则上可以在较大温度密度范围内给出可靠结果,但由于计算量太大以及高温下的计算存在收敛问题,也较难应用到温度较高的稠密等离子体区域.半经验的经典分子动力学方法虽然简单、计算量小,但只能在一定的区域范围内给出较精确的状态方程结果.在不同温度密度区域内采用不同的计算模型,再在空白区域进行插值从而得到全局状态方程在目前不失为一种简单有效的方法.     

2-羟基-1-萘醛缩对氨基水杨酸希夫碱的合成、表征及性质

合成2-羟基-1-萘醛对氨基水杨酸新型水杨酸类希夫碱(HL),通过紫外吸收法、红外光谱法、元素分析法、高分辨质谱对其进行结构表征.利用荧光光谱法,采用Stern-Volmer方程、双对数回归曲线模型处理数据,得出不同温度下HL与牛血清白蛋白(BSA)的结合常数、结合位点数和相关热力学参数,所得热力学数据表明HL与BSA结合方式主要为疏水作用.     

常用制冷工质稠密流体的黏度推算方法

本文通过关联无量纲化剩余黏度与对比密度的关系,提出了一种推算常用制冷工质稠密流体黏度的维里型黏度状态方程.应用该方程只需已知该工质的临界参数、分子量和偏心因子即可完成计算,使得迁移性质的计算在热力学面上和平衡性质的计算保持了完整的一致性.本文通过上述方法计算了9种常用制冷工质的液相黏度,与实验数据比较显示,总平均偏差为2.36%,最大偏差为27.6%.     

高含硫天然气中硫溶解度的热力学一致性评估

甲烷、二氧化碳以及硫化氢是高含硫天然气的主要成分,准确预测硫在天然气中溶解度是高含硫天然气藏开发中最关键问题之一。由于硫化氢的毒性与腐蚀性以及实验通常要在高温高压下进行,目前关于硫在高含硫天然气中溶解度实验数据极其有限。本文针对现有文献中已有的硫在甲烷、二氧化碳以及硫化氢中溶解度的实验数据进行了热力学一致性评估。采用Peng-Robinson状态方程、Wong-Sanlder混合法则以及Van Laar模型建立热力学模型,模型所需要参数由遗传算法拟合得到。计算结果显示,现有的实验数据中,28%满足热力学一致性,44%不完全满足热力学一致性,28%不满足热力学一致性。     

超临界CO2热力学性质的理论计算

应用BWR方程在温度为310～600 K、压强为75～300 bar范围内拟合的超临界CO2流体状态方程,计算了超临界状态下CO2体系的熵、热容和焓.研究表明,这些热力学函数具有明显的超临界特性;与文献值相比,超临界状态下CO2熵的相对误差小于0 .4%,而定压热容的相对误差稍大,为2.45%(T:330～360 K),其数据为进一步从理论上研究超临界CO2与金属铀表面反应的热力学行为奠定了基础.     

氦-3状态方程研究进展第二部分:正常液相区和气体区以及全区间状态方程

宽温度和压力范围的3He详细热力性质数据对进行极低温基础科学研究和制冷特性研究是至关重要的.但至今尚缺乏一个热力学统一的解析形式状态方程,来准确描述1K左右到室温300K大温区的3He热力学性质.在收集和整理各类研究3He热力性质文献的基础上,总结了正常液相区和气体区以及全区间3He状态方程的研究状态,这项工作不仅能为关心3He局部区域性质的研究人员提供总结,而且可为今后开发宽范围的3He热力学状态方程提供参考.     

高压下单晶LiF的光学及热力学性质的密度泛函理论研究

采用平面波赝势密度泛函方法,对单晶氟化锂(LiF)在0~500 GPa静水压下的光学性质进行了理论研究,并利用Vinet状态方程和准简谐Debye模型得到了其热力学性质.理论计算结果表明单晶氟化锂(LiF)在0~500 GPa静水压范围内具有良好的透明性,吸收波段随压强的增加而出现了蓝移.计算所得晶格常数、体积模量及其对压强的一阶导数与实验值相符合.     

二甲醚专用状态方程的研究

在对二甲醚实验数据进行文献调研的基础上,运用生物进化优化算法开发了二甲醚的饱和蒸汽压、饱和液密度及饱和汽密度方程和 Helmholtz 状态方程.其中二甲醚的饱和蒸汽压、饱和液密度和饱和汽密度方程的平均绝对偏差分别为 0.50%、0.38%和 0.55%.新的 Helmholtz 状态方程计算密度的偏差在液相区为 0.1%以内,临界点附近为 l%,可以很好地用于工程计算.     

Development of a perturbed hard-sphere equation of state for pure and mixture of ionic liquids

A perturbed hard-sphere equation of state (PHS EOS) was previously proposed to present the volumetric properties of ionic liquids by employing a variable parameter β being a function of acentric factor to justify the range of vdW dispersion forces (M. M. Papari, J. Moghadasi, S. M. Hosseini, F. Akbari, J. Mol. Liq. 158 (2011) 57–60). The main aim of the present study is to revise an attractive part of the preceding EOS by re-evaluating the above-mentioned variable parameter as well as the repulsive term. Two temperature-dependent parameters appearing in the revisited EOS have been determined from the corresponding states correlations using the interfacial properties of ILs, i.e., surface tension and liquid density, both at room temperature. The revisited EOS has been employed to model the volumetric properties of ionic liquids (ILs). The predictive power of the proposed model has been assessed by comparing the results obtained with 2189 experimental data points related to 24 ILs over a broad range of pressures and temperatures. The overall average absolute deviation (AAD) of the calculated densities from literature data was found to be 0.62 %. Furthermore, the revisited PHS EOS has been employed to model the volumetric properties of 23 mixtures including IL + IL and IL+ solvent over the vast range of temperatures. From 1580 data points of the binary mixtures of interest, the AAD of the correlated densities from the measurements was found to be 0.47 %.     

Application of a new equation of state to energy carriers

A new equation of state (IR EOS) recently reported for liquids and gases has been utilized to predict the densities of some energy carriers at different temperatures, pressures. The ability of IR EOS is examined by comparing its results with experimental data for some energy carriers in homogeneous gas, homogeneous liquid and gas–liquid transition region from low to very high pressures. The IR EOS gives excellent results in homogenous gas and homogeneous liquid region while its predictions in gas–liquid transition have more deviations. The average absolute deviation between calculated and experimental densities for 968 data points of 12 energy carriers is 0.33% over the entire range of data with a maximum pressure of 1000 MPa.     

Correlation of volumetric properties of binary mixtures of some ionic liquids with alcohols using equation of state

In our previous paper, we extended the Tao and Mason equation of state (TM EOS) to pure ionic liquids. Here we apply TM EOS based on statistical?Cmechanical perturbation theory to binary mixtures of ionic liquids. Three temperature-dependent quantities are needed to use the equation of state: the second virial coefficient, B ₂, effective van der Waals co-volume, b, and a scaling factor, ??. The second virial coefficients are calculated from a correlation that uses the normal boiling temperature and normal boiling density. ?? and b can also be calculated from the second virial coefficient by scaling. In this procedure, the number of input parameters, for calculation of B ₂, ??, and b reduced from 5 (i.e., critical temperature, critical pressure, acetric factor, Boyle temperature T _B, and the Boyle volume ?? _B) to 2 (i.e., T _bp and ?? _bp). At close inspection of the deviations given in this work, the TM EOS predicts the densities with a mean AAD of 1.69%. The density of selected system obtained from the TM EOS has been compared with those calculated from perturbed-hard-sphere equation of state. Our results are in favor of the preference of the TM EOS over another equation of state. The overall average absolute deviation for 428 data points that calculated by perturbed-hard-sphere equation of state is 2.60%.     

Equation of state for pure fluids at critical temperature

In this paper, we employ the concept of probability for creating a cavity with diameter d in fluid along with the perturbation and variation approach, and develop an equation of state (EOS) for a hard sphere (HS) and Lennard– Jones (LJ) fluids. A suitable axiomatic form for surface tension S(r) is assumed for the pure fluid, with r as a variable. The function S(r) has an arbitrary parameter m. S(r) = A + B(d/r)/[1 + m(d/r)]. We use the condition in terms of radial distribution function G(λd, η) containing the self-consistent parameter λ and the condition of continuity at r = d/2 to determine A and B. A different EOS can be obtained with a suitable choice of m and the EOS has a lower root-mean-square deviation than that of Barker–Henderson BH2 for LJ fluids.     

Modification of Tao–Mason equation of state to ionic liquids

In our previous paper, we extended the Tao and Mason equation of state (TM EOS) to refrigerant fluids, using the speed of sound data. Here, we predict the equation of state for ionic liquids (ILs). The considered ILs are [Bmim][PF₆], [C₂mim][NtF₂], [C₃mim][NtF₂], [C₆mim][NtF₂], [C₇mim][NtF₂], [C₂mim][EtOSO₃], [Bmim][MeSO₄], [Bmim][OcSO₄], and [C₄mim][dca]. The equation of state consists of three temperature-dependent parameters: the second virial coefficient, a constant for scaling the softness of repulsive force, and an effective hard-sphere diameter equivalent to the van der Waals co-volume. The second virial coefficients of ILs are scare and there is no accurate potential energy function to allow their theoretical calculation. In this work, the second virial coefficient have been calculated using corresponding states correlation based on temperature and density at normal boiling point. The other two parameters of the equation of state can be calculated using a scaling rule. Analysis of our predicted results shows that the Tao?CMason equation of state is capable of accurately predicting the density of ILs at any temperature and pressure. The overall average absolute deviation densities for 1,633 data points are 2.05%. Also, the density of ILs obtained from the TM EOS has been compared with those calculated from vdW?CCS?C?? and Peng?CRobinson (PR) equation of state. Our results are in favor of the preference of the TM EOS over the two other equations of state. The overall average absolute deviation for 1,633 data points calculated by vdW?CCS?C?? and PR equation of state are 6.63% and 12.19%, respectively.     

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。     

Thermal equation of state, and melting and thermoelastic properties of bcc tantalum from molecular dynamics

We performed molecular dynamics simulations with the extended Finnis-Sinclair (EFS) potential to investigate thermal equation of state (EOS), and melting and thermoelastic properties of tantalum. The agreement of the obtained thermal EOS with experiments at ambient conditions is reasonably good. The EFS potential with the two-phase method also reproduced very satisfyingly the high-pressure melting curve, excellently consistent with both the experiments of melting temperature at ambient pressure and shock melting at high pressure. From molecular dynamics simulations, we also obtained the thermoelastic properties of Ta for temperatures up to 3000 K at ambient pressure. Fully including anharmonic effects in molecular dynamics, our calculated elastic constants are in excellent agreement with experimental data. Shear modulus G decreases quickly with increasing temperature.     

Intermolecular interaction potentials of methane－argon complex calculated using LDA approaches

The intermolecular interaction potential for methane－argon complex is calculated by local density approximation (LDA) approaches. The calculated potential has a minimum when the intermolecular distance of methane－argon complex is 6.75 a.u.; the corresponding depth of the potential is 0.0163eV which has good agreement with experimental data. We also have made a nonlinear fitting of our results for the Lennard-Jones (12-6) potential function and obtain that V(R)=143794365.332/R^{12}-3032.093 / R^6 (R in a.u. and V(R) in eV).     

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.     

Thermophysical properties of ionic liquids and their mixtures from a new equation of state

In our previous work, a perturbed hard-trimer-sphere equation of state (PHTS EOS) was developed for modeling the phase equilibria of pure ionic liquids (ILs) (M.M. Alavianmehr et al., Ionics 22 (2016) 2447–2459). In this work, we have successfully extended the model to the mixtures of IL + IL and IL + solvent. Two temperature-dependent parameters appearing in the EOS are correlated with two microscopic scaling constants σ, the effective hard-sphere diameter, and ε, the non-bonded interaction energy. The overall average absolute deviation (AAD) of the estimated densities from the literature data using the proposed model with and without non-additivity parameter (λ _ij) was found to be 0.44 and 0.79%, respectively. A modified Enskog equation and rough hard-sphere (RHS) theory are combined with our proposed equation of state to calculate the viscosity coefficient of ionic liquids and their mixtures. Finally, from the results obtained, a linear relation between logarithm of surface tension and viscosity property of ionic liquid was developed.