Ichiro Fujihara

Excess enthalpies of trans-decalin + benzene, + toluene, + iso-octane, and + heptane at 298.15 K

Abstract Excess molar enthalpies of trans-decalin + benzene, + toluene, + iso-octane, and + heptane were measured at 298.15 K, with a flow microcalorimeter having newly constructed piston-displacement pumps. The HmE values for (trans-decalin + arene) are large and positive; those for (trans-decalin + alkane) are small. The sign of HmE for (trans-decalin + heptane) was found to be negative.

Molar excess volumes of trans-decalin+benzene, +toluene, +isooctane and +n-heptane at 298.15 K

Abstract The molar excess volumes of the trans-decalin+benzene, +toluene, +isooctane and +n-heptane systems have been measured at 298.15 K. The experimental results are analyzed using the Flory and the Sanchez-Lacombe solution theories. The effects of the sizes and shapes of the component molecules and of the interaction energy in the systems are discussed.

Excess properties of Lennard-Jones binary mixtures from computer simulation and theory

Monte Carlo simulation and theory are used to calculate the excess thermodynamic properties of binary mixtures of spherical Lennard-Jones molecules. We study the excess functions of three binary mixtures characterized by the following size and dispersive energy ratios: (1) (σ22/σ11)3 = 2 and ε22/ε11 = 2; (2) (σ22/σ11)3 = 1 and ε22/ε11 = 1/2 and (3) (σ22/σ11)3 = 1/2 and ε22/ε11 = 2. In all cases, the unlike size parameter, σ12, is kept constant and equal to the value given by the Lorentz combining rule (σ12 = (σ11 + σ22)/2). However, different unlike dispersive energy parameter values are considered through the following combining rules: (a) ε12 = (ε11ε22)1/2 (Berthelot rule); (b) ε12 = ε11 (association); and (c) ε12 = ε22 (solvation). The pressure and temperature dependence of the excess volume and excess enthalpy is studied using the NpT Monte Carlo simulation technique for all the systems considered. Additionally, the simplest conformal solution theory is used to check the adequacy of this approach in predicting the excess properties in a wide range of thermodynamic conditions and variety of binary mixtures. In particular, we have applied the van der Waals one-fluid theory to describe Lennard-Jones binary mixtures through the use of the Johnson et al. [1993, Molec. Phys., 78, 591] Helmholtz free energy. Agreement between simulation results and theoretical predictions is excellent in all cases and thermodynamic conditions considered. This work confirms the applicability of the van der Waals one-fluid theory in predicting excess thermodynamic properties of mixtures of spherical molecules. Furthermore, since binary mixtures of spherical Lennard-Jones molecules constitute the reference fluid to be used in perturbation theories for complex fluids, such as the statistical association fluid theory (SAFT), this work shows clearly the applicability of the conformal solution theory within the framework of SAFT for predicting excess functions.

Thermodynamic properties of decalins mixed with hexane isomers at 298.15 K. II. Excess volumes and isentropic compressibilities

Abstract Excess volumes V E and differences in isentropic compressibilities between the solution and the pure state, Δκ s , have been determined at 298.15 K for decalins mixed with hexane isomers. The maximum values of V E are found to correlate linearly with differences of κ s of the pure component liquids. The Δκ s results were used for further detailed discussion of V E . The experimental results are also analysed by using the Flory—Patterson—Prigogine(FPP) theory.

Molar excess enthalpies of cis-decalin + benzene, + toluene, +isooctane and +heptane at 298.15 K

Molar excess enthalpies HE of cis-decalin + benzene, +toluene, +isooctane and +heptane mixtures have been measured by an LKB flow microcalorimeter at 298.15 K. The experimental results are analyzed using the Flory-Patterson-Prigogine theory. The isomer effect of decalin molecule and the effect of the molecular size and shape of the component molecules are discussed.

Excess thermodynamic properties of (cis-decalin or trans-decalin + cyclohexane or methylcyclohexane or cyclooctane) at 298.15 K

Abstract Excess molar enthalpies, excess molar isobaric heat capacities, excess molar volumes, and changes of isentropic compressibility of ( cis -decalin or trans -decalin + cyclohexane or methylcyclohexane or cyclooctane) were measured at 298.15 K. They were not very large in magnitude but showed interesting composition dependences.

Excess volumes of cis-decalin + benzene, + toluene, + isooctane, and + n-heptane at 298.15 K

Abstract Excess molar volumes of cis-decalin + benzene, + toluene, + isooctane, and + n-heptane were measured at 298.15 K. The results were compared with those of the corresponding trans-decalin mixtures reported previously.(1)

Excess molar isobaric heat capacities and isentropic compressibilities of (cis- or trans-decalin + benzene or toluene or iso-octane or n-heptane) at 298.15 K

Abstract Excess molar isobaric heat capacities and isentropic compressibilities of ( cis - or trans -decalin + benzene or toluene or iso-octane or n -heptane) were measured at 298.15 K. The results are compared with excess enthalpies and excess volumes reported previously.

PVT relation and density-dependent local composition for super-critical and sub-critical fluid mixtures of Lennard-Jones molecules

Abstract Molecular dynamics and Monte Carlo calculations have been carried out for Lennard-Jones fluid mixtures. The results of following three calculations are presented and discussed. They are (1) the PVT relationship for the LB-2-1 model and its two pure components in a wide range of pressure and temperature, (2) the dependence of local compositions on the density (pressure) for the LB-2-1 model above and below the critical point, and (3) the effect of attractive interaction on the local compositions for the LB-2-1 and related models. It is found that computer simulation can give the PVT relationship of model fluids which might be used as that of real fluids and their mixtures with appropriate set of parameters. It is also revealed that the density dependence of local compositions is fairly large especially in lower temperatures. Finally, new results for the local composition in LB-2-1 model coincide with those reported recently by Hoheisel and Kohler.

A COMPARISON OF NON-EQUILIBRIUM MOLECULAR DYNAMICS AND NPT MONTE CARLO METHODS FOR MIXING PROPERTIES AND PARTIAL MOLAR QUANTITIES

Non-equilibrium molecular dynamics (NEMD) and NPT Monte Carlo simulations were carried out for two non-ideal Lennard-Jones/spline mixtures at supercritical temperatures. The systems were chosen so that one of them showed positive and the other negative excess volumes and enthalpies on mixing. A strong composition gradient was generated in the NEMD simulations, such that the entire composition range from pure component 1 to pure component 2 was covered in the molecular dynamics cell. A series of Monte Carlo simulations was made, covering the same composition range. The temperatures and pressures used in the MC simulations were chosen equal to the results from the NEMD simulations. The excess volumes and enthalpies on mixing from the two simulations showed excellent agreement, leading to the conclusion that the NEMD simulations were performed under local equilibrium despite the lack of overall equilibrium in the system. Excess and partial molar quantities were computed by the two methods, sand the data were...