A theoretical investigation on the honeycomb potential fluid.
A theoretical investigation on the honeycomb potential fluid.
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DOI：
10.1063/1.3486570
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发表时间：
2010-10
期刊：
影响因子：
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通讯作者：
Shiqi Zhou
中科院分区：
文献类型：
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作者：
Shiqi Zhou
提出了一种局域自洽的奥恩斯坦 - 泽尼克（OZ）积分方程理论（IET），该理论无需借助传统的热力学积分，就能为体相图中任何热力学稳定或亚稳状态点快速获取热力学和结构信息。针对最近提出的三维蜂窝势，开展了大量的正则系综蒙特卡罗（NVT - Monte Carlo）模拟，以检验该理论的可靠性。模拟量包括径向分布函数（rdf）、超额内能、压力、超额化学势和超额亥姆霍兹自由能。结果表明：（i）仅当体相状态未深入两相共存区时，该理论对径向分布函数的再现效果才十分令人满意；（ii）在所研究的四个热力学量中，超额内能是唯一能被当前理论最精确预测的量，理论计算对模拟压力有所高估，但随着温度升高，偏差趋于消失；（iii）利用当前局域自洽OZ IET的结构函数，由本文作者先前推导的一个局域表达式在计算超额化学势时，甚至比用于计算压力的精确维里压力公式精度更高，并且由于误差的抵消，由此得到的超额亥姆霍兹自由能与模拟结果惊人地一致。基于上述观察，建议在OZ IET框架内，沿等容线对理论超额内能进行积分以得到超额亥姆霍兹自由能，然后将其拟合成多项式，用于计算其他所有热力学量，这或许是一个不错的方法。
A local self-consistent Ornstein-Zernike (OZ) integral equation theory (IET) is proposed to provide a rapid route for obtaining thermodynamic and structural information for any thermodynamically stable or metastable state points in the bulk phase diagram without recourse to traditional thermodynamic integration, and extensive NVT-Monte Carlo simulations are performed on a recently proposed honeycomb potential in three dimensions to test the theory's reliability. The simulated quantities include radial distribution function (rdf) and excess internal energy, pressure, excess chemical potential, and excess Helmholtz free energy. It is demonstrated that (i) the theory reproduces the rdf very satisfactorily only if the bulk state does not enter deep into a two phases coexistence region; (ii) the excess internal energy is the only one of the four thermodynamic quantities investigated amenable to the most accurate prediction by the present theory, and the simulated pressure is somewhat overestimated by the theoretical calculations, but the deviation tends to vanish along with rising of the temperature; (iii) using the structural functions from the present local self-consistent OZ IET, a previously derived local expression, due to the present author, achieves even a higher accuracy in calculating for the excess chemical potential than the exact virial pressure formula for the pressure, and the resulting excess Helmholtz free energy is in surprisingly same with the simulation results due to offset of the errors. Based on the above observations, it is suggested that it may be a good procedure to integrate the theoretical excess internal energy along the isochors to get the excess Helmholtz free energy, which is then fitted to a polynomial to be used for calculation of all of other thermodynamic quantities in the framework of the OZ IET.