Yoshimori Miyano

An effective triplet potential for argon

Abstract Miyano Y., 1994. An effective triplet potential for argon. Fluid Phase Equilibria , 95: 31-41. An effective triplet potential is proposed. This triplet potential expresses the effects of Axilrod-Teller three-body interactions on a pair of molecules, and is given as a simple function of density and the distance between the pair of molecules. The computer time for Monte Carlo simulations of fluids with both a pair potential and the effective triplet potential is almost equivalent to that of fluids with only the pair potential. By using an accurate pair potential together with this effective triplet potential, Monte Carlo simulations are performed to estimate the thermodynamic properties of argon, and the results are compared with the experimental properties, the saturated vapor and liquid densities, the heats of varporization and the second virial coefficients. The comparisons show that the simulation results for fluids with only the pair potential give poor agreement with the experimental data, especially for the heats of vaporization where the simulation results give very large deviations. However, the simulation results for fluids with both pair potential and triplet potential give very good agreements with the experimental data of argon.

Equation of state based on the weeks-chandler-andersen perturbation theory

Abstract An equation of state based on the Weeks-Chandler-Andersen (WCA) perturbation theory utilizing the simplified random-phase approximation (RPA) term is p of state is applied successfully to calculate the P-V-T relationship for a spherical molecule, argon. For nonspherical molecules, the effects of anisotropic interactions are treated empirically. The calculated P-V-T relationships and saturated properties for nonspherical and nonpolar molecules agree well with experimental data. The potential parameters for nonpolar substances are well correlated with the acentric factors.

An equation of state for Lennard-Jones pure fluids applicable over a very wide temperature range

Abstract Miyano, Y., 1993. An equation of state for Lennard-Jones pure fluids applicable over a very wide temperature range. Fluid Phase Equilibria, 85: 71-80. Monte Carlo simulations of the compressibility factor and internal energy of a Lennard-Jones fluid are reported for 112 state conditions over the density range 0.2 ⩽ π★ ⩽ 1.1 and the temperature range 0.45 ⩽ T★ ⩽ 100 (where θ★ = θσ3 and T★ = k T ϵ) . These simulation results for the compressibility factors and internal energies are combined with those of previous workers to derive an equation of state for the Lennard-Jones fluid that is valid over a very wide range of temperatures. The equation of state used is a modified Benedict-Webb-Rubin equation which is similar to that proposed by Nicolas et al. (Nicolas, J.J., Gubbins, K.E., Streett, W.B. and Tildesley, D.J., 1979. Mol. Phys., 37: 1429-1454).

Equation of state calculations and Monte Carlo simulations of internal energies, compressibility factors and vapor-liquid equilibria for Lennard-Jones fluid mixtures

Abstract Miyano, Y., 1994. Equation of state calculations and Monte Carlo simulations of internal energies, compressibility factors and vapor-liquid equilibria for Lennard-Jones fluid mixtures. Fluid Phase Equilibria , 95: 1-13. Internal energies, compressibility factors and vapor-liquid equilibria for Lennard-Jones fluid mixtures are simulated by using Monte Carlo techniques, where the potential parameters ϵ 12 and σ 12 between the different kinds of molecules are much different from the Lorentz-Bertherot rule. These simulations results are used to test the accuracy of the equations of state for the Lennard-Jones fluid mixtures. An accurate equation of state for the Lennard-Jones pure fluid is extended to mixtures by using four different mixing rules; a van der Waals one-fluid model, a modified van der Waals one-fluid model, a mean density approximation and a mixing rule based on the idea of Putting the Advantage of Perturbation theories to Practical Use in a simple form (PAPPU). The Weeks-Chandler-Andersen (WCA) perturbation theory is also tested. Comparison with the computer simulation results shows that the equation of state extended to mixture via the PAPPU mixing rule gives the best results. For mixtures with σ 12 different from the value given by Lorentz-Bertherot rule, the WCA perturbation theory and the equations of state extended to mixtures via these mixing rules give poor results in general.

Intermolecular potential for oxygen

Abstract Monte Carlo simulations for diatomic molecules were performed by using a site-site pair potential model together with a triplet potential. To reduce the computer time, an effective triplet potential is proposed. This potential expresses the effects of Axilrod-Teller three-body interactions on a pair of atoms, and is given as a simple function of density and the distance between the pair of atoms. The computer time for Monte Carlo simulations is almost equivalent to that of fluids with only the site-site pair potential. From comparisons of the Monte Carlo simulations and the experimental data of oxygen, the potential parameters are determined.