Institute of Thermodynamics and Thermal Process Engineering, University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany.
J Chem Phys. 2023 Apr 28;158(16). doi: 10.1063/5.0141856.
We develop a physically based equation of state that describes Mie ν-6 fluids with an accuracy comparable to that of state-of-the-art empirical models. The equation of state is developed within the framework of the uv-theory [T. van Westen and J. Gross, J. Chem. Phys. 155, 244501 (2021)], which is modified by incorporating the third virial coefficient B3 in the low-density description of the model. The new model interpolates between a first-order Weeks-Chandler-Andersen (WCA) perturbation theory at high densities and a modified first-order WCA theory that recovers the virial expansion up to B3 at low densities. A new algebraic equation for the third virial coefficient of Mie ν-6 fluids is developed-other inputs are taken from previous work. Predicted thermodynamic properties and phase equilibria are compared to a comprehensive database of molecular simulation results from the literature, including Mie fluids of repulsive exponents 9 ≤ ν ≤ 48. The new equation of state is applicable to states with densities up to ρ*(T*)⪅1.1+0.12T* and temperatures T* > 0.3. For the Lennard-Jones fluid (ν = 12), the performance of the model is comparable to that of the best empirical equations of state available. As compared to empirical models, the physical basis of the new model provides several advantages, however: (1) the new model is applicable to Mie fluids of repulsive exponents 9 ≤ ν ≤ 48 instead of only ν = 12, (2) the model leads to a better description of the meta-stable and unstable region (which is important for describing interfacial properties by classical density functional theory), and (3) being a first-order perturbation theory, the new model (potentially) allows an easier and more rigorous extension to non-spherical (chain) fluids and mixtures.
我们开发了一种基于物理的状态方程，可以以与最先进的经验模型相当的精度描述 Mie ν-6 流体。该状态方程是在 uv 理论[T. van Westen 和 J. Gross，J. Chem. Phys. 155, 244501 (2021)]的框架内开发的，该理论通过在模型的低密度描述中包含第三维里系数 B3 进行了修改。新模型在高密度下介于一阶威克斯-钱德勒-安德森（WCA）微扰理论和在低密度下恢复到 B3 的修正一阶 WCA 理论之间进行插值。开发了 Mie ν-6 流体的第三维里系数的新的代数方程-其他输入取自以前的工作。预测的热力学性质和相平衡与文献中来自分子模拟的综合数据库进行了比较，包括排斥指数为 9 ≤ ν ≤ 48 的 Mie 流体。新的状态方程适用于密度高达 ρ*(T*)⪅1.1+0.12T和温度 T > 0.3 的状态。对于 Lennard-Jones 流体（ν = 12），该模型的性能与可用的最佳经验状态方程相当。与经验模型相比，新模型具有以下几个优点：（1）新模型适用于排斥指数为 9 ≤ ν ≤ 48 的 Mie 流体，而不仅仅是 ν = 12；（2）该模型导致更好地描述亚稳态和不稳定区域（这对于通过经典密度泛函理论描述界面性质很重要）；（3）作为一阶微扰理论，新模型（潜在地）允许更容易和更严格地扩展到非球形（链）流体和混合物。
