Molar volume for mixtures of methane with krypton,argon, ethane and carbon monoxide using the ISM equation of state

In this paper, an analytical equation of state (EoS) proposed by Ihm–Song–Mason (ISM) was employed to calculate the molar volume of mixtures of methane with krypton, argon, ethane and carbon monoxide. The best available pair interaction potential energy has been used to evaluate the second virial coefficients required by the ISM EoS. The calculated values of second virial coefficients were applied to the ISM EOS to predict the molar volumes for the above mentioned mixtures. Agreement with the experiment is excellent for all systems.     

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%.     

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.     

Analysis of equation of state for nanomaterials

An equation of state (EOS) recently proposed for nanomaterials is discussed critically. Different possible forms of the EOS are discussed with their correlations. We have considered 20 nanomaterials for this purpose, viz. CdSe, Rb₃C₆₀, carbon nanotube, γ-Fe₂O₃, ε-Fe (hexagonal iron), MgO, γ-Al₂O₃ (67 nm), α-Fe₂O₃, α-Fe (filled nanotube), TiO₂ (anatase ), 3C-SiC (30 nm), TiO₂ (rutile phase), Zr_0.1Ti_0.9O₂, γ-Si₃N₄, Ni-filled MWCNT, Fe-filled MWCNT, CeO₂ (cubic fluorite phase and orthorhombic phase), germanium (49 nm), GaN (wurtzite phase) and SnO₂ (rutile phase) (14 nm). It is found that the change in the form of EOS does not improve the results. This demonstrates the validity of the EOS proposed for nanomaterials. The EOS is also used to study the effect of temperature on compression of Ni (20 nm). It is found that there is small shift in isotherm due to increase in the temperature. The results have been found to present a good agreement with the available experimental data.     

Molecular dynamic simulations and global equation of state of square-well fluids with the well-widths from λ = 1.1 to 2.1

We present the results of extensive new molecular dynamic (MD) simulations in the one-phase region for square well fluids with well widths λ?=?1.10, 1.15, 1.20, 1.25, 1.375, 1.50, 1.75, 1.90, 2.0, and 2.10. These data have been used in developing a crossover equation of state (CR EOS) for square-well fluids with well widths 1.1?≤?λ?≤?2.1. The CR EOS incorporates non-analytic scaling laws in the critical region, and in the limit of low densities yields the exact second and third virial coefficients. Also in the high-temperature region, it reproduces first-order perturbation theory results. The CR EOS was tested against our new MD simulations, and earlier MD and Monte-Carlo (MC) simulations reported by other authors as well. Excellent agreement between calculated values and simulation data for all SW fluids is observed. In combination with the density-functional theory, the CR EOS is also capable of reproducing surface tension simulations with high accuracy. Application of the CR EOS for solid–liquid equilibrium calculations in combination with the Lennard–Jones and Devonshire cell model for the solid phase, is also discussed.     

Structure,equation of state and elasticity of crystalline HNIW by molecular dynamics simulations

We have performed theoretical investigations on the structure, equation of state (EOS), elasticity, and mechanical properties of 2, 4, 6, 8, 10, 12-Hexanitrohexaazaisowurzitane (HNIW) energetic material by molecular dynamics (MD) simulations. The lattice parameters and equations of state of the four polymorphs (ε-, γ-, β-, and α-HNIW) under high pressure are calculated. Our calculated results agree with the previous experiments and theoretical calculations. Meanwhile, the elastic constants and some other mechanical properties of the most stable ε-HNIW under high pressure and temperature are predicted successfully.     

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.     

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。     

一种简化维里型状态方程预测高温甲烷PVT关系

为满足描述爆轰环境下高温气体高温、中高压状态的需求,本文提出了一种基于Lennard-Jones(LJ)势能函数的简化维里型状态方程Han-Long(HL).应用HL状态方程计算了甲烷1000 K以上112组理论和实验数据,计算所得体积平均绝对偏差约为1%,最大误差为3.28%,远低于DMW状态方程和BS状态方程的计算偏差.采用HL状态方程计算了甲烷冲击试验的热力学数据,计算所得体积偏差均小于3%.结果表明,HL状态方程能够很好的描述高温甲烷的热力学状态.     

The 2‐matrix of the spin‐polarized electron gas: contraction sum rules and spectral resolutions

The spin‐polarized homogeneous electron gas with densities ρ_↑ and ρ_↓ for electrons with spin ‘up’ (↑) and spin ‘down’ (↓), respectively, is systematically analyzed with respect to its lowest‐order reduced densities and density matrices and their mutual relations. The three 2‐body reduced density matrices γ_↑↑, γ_↓↓, γ_a are 4‐point functions for electron pairs with spins ↑↑, ↓↓, and antiparallel, respectively. From them, three functions G_↑↑(x,y), G_↓↓(x,y), G_a(x,y), depending on only two variables, are derived. These functions contain not only the pair densities according to g_↑↑(r) = G_↑uarr;(0,r), g_↓↓(r) = G_↓↓(0,r), g_a(r) = G_a(0,r) with r = | r ₁ ‐ r ₂|, but also the 1‐body reduced density matrices γ_↑ and γ_↓ being 2‐point functions according to γ_s = ρ_sf_s and f_s(r) = G_ss(r, ∞) with s = ↑,↓ and r = | r ₁ ‐ r ^′₁|. The contraction properties of the 2‐body reduced density matrices lead to three sum rules to be obeyed by the three key functions G_ss, G_a. These contraction sum rules contain corresponding normalization sum rules as special cases. The momentum distributions n_↑(k) and n_↓(k), following from f_↑(r) and f_↓(r) by Fourier transform, are correctly normalized through f_s(0) = 1. In addition to the non‐negativity conditions n_s(k),g_ss(r),g_a(r) ≥ 0 [these quantities are probabilities], it holds n_s(k) ≤ 1 and g_ss(0) = 0 due to the Pauli principle and g_a(0) ≤ 1 due to the Coulomb repulsion. Recent parametrizations of the pair densities of the spin‐unpolarized homogeneous electron gas in terms of 2‐body wave functions (geminals) and corresponding occupancies are generalized (i) to the spin‐polarized case and (ii) to the 2‐body reduced density matrix giving thus its spectral resolutions.     

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.     

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.     

Corrections to scaling in the q-state Potts model within Gaussian closure approximation

Corrections to scaling in the q-state Potts model due to departures of the initial condition from scaling morphology are studied at zero temperature in phase-ordering kinetics within Gaussian closure approximation. When the corrections to scaling are included, the equal time correlation function has the form G(r,t) = g₀(r/L)+L^-ωg₁(r/L) + ..., where L is the coarsening length scale. Both the correction-to-scaling exponent ω and the correction-to-scaling function g₁(x) are calculated for different values of q. The correction-to-scaling exponent ω is found to be nontrivial and depends on q. The corrections to scaling are found to be large (relative to scaling function g₀(x) itself) at large scaling variable x.     

Li2O-2B2O3熔体的物性研究

系统测量了四硼酸锂(Li₂Ｏ-２Ｂ_２Ｏ_３)熔体的密度ρ、表面张力γ随着温度的变化规律，实验结果表明在1100K到1500K范围内Li₂Ｏ-２Ｂ_２Ｏ_３高温熔体的密度和表面张力随着温度的升高均线性减小.通过实验数据拟合得出熔体密度与温度关系为ρ(T)=2.574—4.89×１０^－４T，熔点处Li₂Ｏ-２Ｂ_２Ｏ关键词： 功能晶体 四硼酸锂 密度 表面张力     

四体相互作用对固氦压缩特性的贡献

运用从头计算自洽场方法和原子团簇理论计算了高压下固氦原子间的四体势分量.计算结果表明四体分量对结合能的贡献为正；随着压缩度增大四体势的贡献比例变大.采用两体、三体、四体势和Aziz吸引势计算固氦零温状态方程并与实验测量相比较，结果表明两体势对固氦的压缩性贡献了过多的正效应，加入三体分量的修正，仅在低于10GPa时理论值与实验值相符很好，但考虑了四体势修正后能将理论值与实验值符合程度提高到 27GPa. 关键词： 状态方程 固氦 四体势 从头计算     

Variable-range hopping conduction in LaMnO<Subscript>3 + δ</Subscript>

The temperature dependence of the electrical resistivity ρ(T) for ceramic samples of LaMnO_{3 + δ} (δ = 0.100–0.154) are studied in the temperature range T = 15–350 K, in magnetic fields of 0–10 T, and under hydrostatic pressures P of up to 11 kbar. It is shown that, above the ferromagnet-paramagnet transition temperature of LaMnO_{3 + δ}, the dependence ρ(T) of this compound obeys the Shklovskii-Efros variable-range hopping conduction: ρ(T) = ρ₀(T)exp[(T ₀/T)^1/2], where ρ₀(T) = AT ^9/2 (A is a constant). The density of localized states g(?) near the Fermi level is found to have a Coulomb gap Δ and a rigid gap γ(T). The Coulomb gap Δ assumes values of 0.43, 0.46, and 0.48 eV, and the rigid gap satisfies the relationship γ(T) ≈ γ(T _v)(T/T _v)^1/2, where T _v is the temperature of the onset of variable-range hopping conduction and γ(T _v) = 0.13, 0.16, and 0.17 eV for δ = 0.100, 0.125, and 0.154, respectively. The carrier localization lengths a = 1.7, 1.4, and 1.2 Å are determined for the same values of δ. The effect of hydrostatic pressure on the variable-range hopping conduction in LaMnO_{3 + δ} with δ = 0.154 is analyzed, and the dependences Δ(P) and γ_v(P) are obtained.     

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。     

Critical correlation function to order ϵ3

The zero-field, two-point correlation function of an n-vector system in d = 4 ? ?dimensions is calculated to order ?³ for T ? T_c, using a dispersion theory approach to the scaling function g(g²ξ²)     

Band structure and properties of polymorphic modifications of lower tungsten carbide W<Subscript>2</Subscript>C

The structural and electronic properties are investigated and the relative stabilities of all the known polymorphic modifications (α, β, γ, ?) of the lower tungsten carbide W₂C are numerically estimated using the ab initio full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA) of the local spin density. The equilibrium parameters of the crystal lattices, the band structures, and the total and partial densities of states are determined for the first time within a unified approach. The energies of formation of the α, β, γ, and ? polymorphic modifications of the lower tungsten carbide [in the reactions W₂C ? 2W + C (graphite)] are calculated and used to discuss their relative stabilities.     

Theoretical investigation of electron paramagnetic resonance parameters and lattice distortion in α-Al2O3 crystal doped with V3+ ions

The electron paramagnetic resonance parameters D, g _∥ and g _⊥ for V³⁺ ions in α-Al₂O₃ crystals are calculated on the basis of the complete diagonalization method and the superposition model. In the calculation, the contributions of the variation of the cation–ligand bond lengths and bond angles are taken into consideration. The calculated results agree well with the experimental data. Our investigation shows that the local structure around the V³⁺ ions possesses a compressed trigonal distortion above the O^2?-triangle and an elongated trigonal distortion in the lower one.