Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran.
Molecular Simulation Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114, Iran.
J Chem Phys. 2018 Mar 14;148(10):104502. doi: 10.1063/1.5018789.
Based on Wertheim's second order thermodynamic perturbation theory (TPT2), equations of state (EOSs) are presented for the fluid and solid phases of tangent, freely jointed spheres. It is considered that the spheres interact with each other through the Weeks-Chandler-Anderson (WCA) potential. The developed TPT2 EOS is the sum of a monomeric reference term and a perturbation contribution due to bonding. MC NVT simulations are performed to determine the structural properties of the reference system in the reduced temperature range of 0.6 ≤ T* ≤ 4.0 and the packing fraction range of 0.1 ≤ η ≤ 0.72. Mathematical functions are fitted to the simulation results of the reference system and employed in the framework of Wertheim's theory to develop TPT2 EOSs for the fluid and solid phases. The extended EOSs are compared to the MC NPT simulation results of the compressibility factor and internal energy of the fully flexible chain systems. Simulations are performed for the WCA chain system for chain lengths of up to 15 at T* = 1.0, 1.5, 2.0, 3.0. Across all the reduced temperatures, the agreement between the results of the TPT2 EOS and MC simulations is remarkable. Overall Average Absolute Relative Percent Deviation at T* = 1.0 for the compressibility factor in the entire chain lengths we covered is 0.51 and 0.77 for the solid and fluid phases, respectively. Similar features are observed in the case of residual internal energy.
基于 Wertheim 的二阶热力学微扰理论（TPT2），本文提出了切线自由连接球体的流体相和固体相的状态方程（EOS）。考虑到球体之间通过 Weeks-Chandler-Anderson（WCA）势能相互作用。所开发的 TPT2 EOS 是单体参考项和键合引起的微扰贡献的总和。进行 MC NVT 模拟，以在 0.6≤T*≤4.0 的降低温度范围和 0.1≤η≤0.72 的堆积分数范围内确定参考系统的结构性质。对参考系统的模拟结果进行数学函数拟合，并在 Wertheim 理论的框架内，为流体相和固体相开发 TPT2 EOS。将扩展的 EOS 与完全柔性链系统的 MC NPT 模拟压缩因子和内能结果进行比较。在 T*=1.0、1.5、2.0、3.0 下，对 WCA 链系统进行模拟，链长可达 15。在所有降低温度下，TPT2 EOS 和 MC 模拟结果之间的一致性非常显著。在我们涵盖的整个链长范围内，压缩因子的总体平均绝对相对偏差在 T*=1.0 时分别为 0.51 和 0.77，分别适用于固体相和流体相。在剩余内能的情况下，也观察到类似的特征。
