J. Phys. Soc. Jpn. 74, pp. 2459-2474 (2005) [16 Pages]
FULL PAPERS

Solvophobic Effects on an Infinitely-Thin Hard Needle in a Two-Dimensional Square-Well Fluid

+ Affiliations
1Department of Chemistry, Faculty of Science, Kyoto University, Kyoto 606-8502

Solvophobic effects on an infinitely-thin hard needle in two-dimensional square-well fluids are studied with an analytical expansion and a Monte Carlo (MC) calculation on the chemical potential from the gaseous to liquid densities. The analytical expansion is made for a short needle with respect to the needle length. The solvophobic effects on an extremely short needle is correlated with those on the radial distribution function between solvent disks at the contact distance. The solvophobic solvation on a short needle is exothermic, i.e., the chemical potential of the needle decreases with the increase in the solvent–solvent interaction, at low densities, while it is endothermic at high densities. The solvophobic interaction between short needles can be attractive or repulsive depending on the configuration of the interacting needles as well as the density region of the fluid. The solvophobic effects on a hard needle of finite length are evaluated by a MC method through the free-path distribution of a small and light particle in the square-well fluid. The MC calculation shows that the solvophobic solvation is exothermic even at high densities, when the needle is sufficiently long. The exothermic behavior is apparently due to a long range component evolved with the elongation of the needle. The solvophobic interaction at high densities changes its characteristics with the needle length also.

©2005 The Physical Society of Japan

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