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Thermodynamic Properties and Phase Equilibrium Study of Lennard-Jones Model and Application to Real Molecules
Author NameAffiliationE-mail
周世琦 Institute of Modern Statistical Mechanics, Zhuzhou Institute of Technology, Zhuzhou 412008 chixiayzsq@yahoo.com 
Abstract:
Both a free volume approach for Helmholtz free energy and a theoretically-based fitted formula for radial distribution function (rdf) of hard sphere solid were employed to describe the Helmholtz free energy of Lennard-Jones (LJ) solid in the framework of first order thermodynamic perturbation theory. Dividing the LJ potential follows from a modified WCA prescription, the specification of equivalent hard sphere diameter was determined by a simple iteration procedure devised originally for liquid state, but extended to solid state in the present study. Two hundred shells were used in the rdf to get an accurate perturbation term. Bulk fluid thermodynamic property of the LJ model is from a recently proposed equation of state. The present approach is very accurate for the description of excess Helmholtz free energy and equation of state of LJ solid, but shows some deviation from the simulation for excess Helmholtz free energy of uniform LJ fluid when the reduced temperature is lower than 0.75. The present approach is satisfactory for description of phase equilibrium of the LJ model. By choosing the appropriate LJ potential parameter, the present approach can describe the melting curve of real molecules accurately.
Key words:  Solid-liquid coexistence, Thermodynamic perturbation theory, Free volume
FundProject:
LJ模型的热力学特性、相平衡及用于真实分子的研究
周世琦
摘要:
结合描述硬球固体Helmholtz自由能的自由体积方法与描述硬球固体径向分布函数的拟合的分析表达式与一阶热力学摄动理论,用于描述Lennard-Jones(LJ)固体的Helmholtz自由能.按照一个修正的WCA方法将LJ势分为短程排斥部分与长程吸引部分,将文献中一个用于求取液相的等价的硬球直径的简单的迭代法扩展到固相,用于求取固相的等价的硬球直径.在固体Helmholtz自由能的计算中,使用200壳层,以便获得精确的结果.体相LJ液体的热力学特性由一个最近提出的状态方程求取.该方法很好地描述了LJ固体
关键词:  固-液相变  热力学摄动理论  自由体积
DOI:10.1088/1674-0068/18/4/487-494
分类号: