Congruent Chemical Potentials and Insertion Works in Establishing Nonuniform-Fluid Structures via Uniform-Fluid Properties
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- 作者：Lloyd L. Lee
- 刊名：Journal of Chemical & Engineering Data
- 出版年：2014
- 出版时间：April 10, 2014
- 年：2014
- 卷：59
- 期：4
- 页码：975-982
- 全文大小：388K
- 年卷期：v.59,no.4(April 10, 2014)
- ISSN：1520-5134
文摘
We propose an effective density 蟻pseudo that engenders direct mapping of the free energy FU of uniform fluids to the free energy FN of nonuniform fluids by requiring FN = FU (at 蟻pseudo). The equality is called the congruence condition. It is made possible by considering the statistical mechanical theory: the potential distribution theorem (PDT). The PDT connects three quantities: the work Wins(z) needed for inserting a test particle into the fluid, the chemical potential 渭0 of the bulk fluid, and the nonuniform singlet density 蟻w(1)(z). We use Monte Carlo (MC) data to obtain the insertion work Wins(z) (via the Euler鈥揕agrange equation) from the probability densities 蟻w(1)(z). The concept of the congruent effective density 蟻pseudo is applicable to general interaction potentials, not restricted to the hard sphere type. We examine thus two simple fluids adsorbed on a hard wall: (i) the hard spheres and (ii) the Lennard-Jones fluid for comparison. We discern the difference in behavior of the effective density vis-脿-vis whether there is enhancement or depletion of the fluid density near the wall (namely, if there is accumulation of molecules at the wall, or if there is deficit of molecules at the wall). 蟻pseudo(z) is found to exhibit for enhanced adsorption out-of-phase oscillations compared to 蟻w(1)(z). For depleted adsorption, we do not observe oscillations, and the trends of 蟻pseudo(z) are in line with those of 蟻w(1)(z). Explanation is sought in terms of the concavity of the chemical-potential function.