C141 エタノール/シクロヘキサン混合溶液構造の溶液モル比率依存性およびエタノール拡散係数変化の分子論的解釈(OS-11 ナノスケール伝熱IV)

Abstract

Until now, huge amount of theoretical study aiming a molecular interpretation of transport properties of a binary liquid has been performed. Whereas the transport properties of a simple binary liquid such as a Lennard-Jones binary liquid can be explained in a molecular level, those of an associated binary fluid such as surfactant/oil mixture and water solution cannot be explained in a general way. This is because the anisotropic hydrogen bonding between their hydrophilic groups results in the formation of molecular clusters having a characteristic shape, and therefore makes it difficult to establish a general model of such a complex liquid. This paper reports the results of a series of the molecular dynamics (MD) studies where the molar fraction of ethanol in ethanol/cyclohexane binary liquid was chosen in a whole range with an increment of 0.1. The OPLS-UA and 6-sited Lennard-Jones were used as a potential model of ethanol and cyclohexane molecules. The NVT (T=298.15K) ensemble was applied with the cubic periodic unit cell. The detection of the hydrogen bonding between the hydroxyl group of ethanol molecule makes it possible to expose the mesoscopic structure of ethanol clusters. On the other hand, a self-diffusion coefficient of ethanol was estimated through the Einstein's formula for every χ_e case. We relate these results and attempt the molecular description of the dependency of the ethanol self-diffusion coefficient on the molar fraction of binary liquid.