Density functional approximation for van der Waals fluids: based on hard sphere density functional approximation
Zhou Shi-Qi(周世琦)†
Laboratory of Green Packaging and Biological Nanotechnology and Institute of Modern Statistical Mechanics, Hunan University of Technology, Zhuzhou 412008, China
Abstract A universal theoretical approach is proposed which enables all hard sphere density functional approximations (DFAs) applicable to van der Waals fluids. The resultant DFA obtained by combining the universal theoretical approach with any hard sphere DFAs only needs as input a second-order direct correlation function (DCF) of a coexistence bulk fluid, and is applicable in both supercritical and subcritical temperature regions. The associated effective hard sphere density can be specified by a hard wall sum rule. It is indicated that the value of the effective hard sphere density so determined can be universal, i.e. can be applied to any external potentials different from the single hard wall. As an illustrating example, the universal theoretical approach is combined with a hard sphere bridge DFA to predict the density profile of a hard core attractive Yukawa model fluid influenced by diverse external fields; agreement between the present formalism's predictions and the corresponding simulation data is good or at least comparable to several previous DFT approaches. The primary advantage of the present theoretical approach combined with other hard sphere DFAs is discussed.
Received: 31 July 2006
Revised: 23 October 2006
Accepted manuscript online:
PACS:
68.08.-p
(Liquid-solid interfaces)
Fund: Project supported by the
National Natural Science Foundation of China (Grant No~20673150).
Cite this article:
Zhou Shi-Qi(周世琦) Density functional approximation for van der Waals fluids: based on hard sphere density functional approximation 2007 Chinese Physics 16 1167
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