Free energy and entropy of a dipolar liquid by computer simulations

Palomar Ricardo; Sese Gemma

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Free energy and entropy of a dipolar liquid by computer simulations

机译：通过计算机模拟自由能量和偶极液的熵

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Thermodynamic properties for a system composed of dipolar molecules are computed. Free energy is evaluated by means of the thermodynamic integration technique, and it is also estimated by using a perturbation theory approach, in which every molecule is modeled as a hard sphere within a square well, with an electric dipole at its center. The hard sphere diameter, the range and depth of the well, and the dipole moment have been calculated from properties easily obtained in molecular dynamics simulations. Connection between entropy and dynamical properties is explored in the liquid and supercooled states by using instantaneous normal mode calculations. A model is proposed in order to analyze translation and rotation contributions to entropy separately. Both contributions decrease upon cooling, and a logarithmic correlation between excess entropy associated with translation and the corresponding proportion of imaginary frequency modes is encountered. Rosenfeld scaling law between reduced diffusion and excess entropy is tested, and the origin of its failure at lowtemperatures is investigated. Published by AIP Publishing.

机译：计算由双极分子组成的系统的热力学性质。通过热力学积分技术评估自由能量，并且还通过使用扰动理论方法估计，其中每个分子在方形阱内被建模为硬球，其中心有电偶极子。井的硬球直径，范围和深度，并且偶极矩已经从分子动力学模拟中容易获得的性质计算。通过使用瞬时正常模式计算，在液体和过冷状态下探讨熵和动态性能之间的连接。提出了一种模型，以便分析翻译和旋转贡献分别熵。遇到了在冷却时降低的两种贡献，并且遇到了与翻译相关联的过量熵与相应比例的虚频模式之间的对数相关性。测试了减少扩散和过量熵之间的Rosenfeld缩放规律，并研究了低温下失效的起源。通过AIP发布发布。

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《The Journal of Chemical Physics》 |2018年第8期|共11页
作者
Palomar Ricardo; Sese Gemma;
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Univ Politecn Cataluna Dept Fis Campus Nord Modul B4 C Jordi Girona 1-3 ES-08034 Barcelona Spain;

Univ Politecn Cataluna Dept Fis Campus Nord Modul B4 C Jordi Girona 1-3 ES-08034 Barcelona Spain;

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正文语种 eng
中图分类物理化学（理论化学）、化学物理学;
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1. Free energy and entropy of a dipolar liquid by computer simulations [J] . Palomar Ricardo, Sese Gemma The Journal of Chemical Physics . 2018,第8期

机译：通过计算机模拟自由能量和偶极液的熵
2. Calculation of the intrinsic solvation free energy profile of methane across a liquid/liquid interface in computer simulations [J] . Mária Darvas, Miguel Jorge, M. Natalia D.S. Cordeiro, Journal of Molecular Liquids . 2014,第Null期

机译：在计算机模拟中计算甲烷在液/液界面上的固有溶剂化自由能分布
3. Calculation of the Intrinsic Solvation Free Energy Profile of an Ionic Penetrant Across a Liquid-Liquid Interface with Computer Simulations [J] . Maria Darvas, Miguel Jorge, M. Natalia D. S. Cordeiro The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical . 2013,第50期

机译：利用计算机模拟计算离子渗透剂在液-液界面上的本征溶剂化自由能分布
4. Calculation of solid-liquid interfacial free energies from atomistic computer simulation [C] . Brian B. Laird, Ruslan L. Davidchack, Yang Yang, International Conference Multiscale Materials Modeling . 2010

机译：原子计算机模拟中固液界面自由能的计算
5. Equilibrium free energy differences from nonequilibrium computer simulations: Improving convergence by reducing dissipation [D] . Vaikuntanathan, Suriyanarayanan 2011

机译：来自非平衡计算机模拟的平衡自由能差异：通过减少耗散来改善收敛
6. Calculationof the Intrinsic Solvation Free EnergyProfile of an Ionic Penetrant Across a Liquid–Liquid Interfacewith Computer Simulations [O] . Mária Darvas, *, Miguel Jorge, -1

机译：计算方式本征溶剂化自由能离子渗透剂跨液-液界面的分布与计算机仿真
7. The thermodynamic changes that occur upon mixing five models of formamide and three models of water, including the miscibility of these model combinations itself, is studied by performing Monte Carlo computer simulations using an appropriately chosen thermodynamic cycle and the method of thermodynamic integration. The results show that the mixing of these two components is close to the ideal mixing, as both the energy and entropy of mixing turn out to be rather close to the ideal term in the entire composition range. Concerning the energy of mixing, the OPLS/AA-mod model of formamide behaves in a qualitatively different way than the other models considered. Thus, this model results in negative, while the other ones in positive energy of mixing values in combination with all three water models considered. Experimental data supports this latter behavior. Although the Helmholtz free energy of mixing always turns out to be negative in the entire composition range, the majority of the model combinations tested either show limited miscibility, or, at least, approach the miscibility limit very closely in certain compositions. Concerning both the miscibility and the energy of mixing of these model combinations, we recommend the use of the combination of the CHARMM formamide and TIP4P water models in simulations of water-formamide mixtures. [O] . Kiss, Bálint, Fábián, Balázs, Idrissi, Abdenacer, 2017

机译：通过使用适当选择的热力学循环和热力学积分方法进行蒙特卡罗计算机模拟，研究了将五种甲酰胺模型和三种水模型混合在一起时发生的热力学变化，包括这些模型组合本身的可混溶性。结果表明这两种组分的混合接近于理想的混合，因为混合的能量和熵在整个组成范围内都非常接近理想的项。关于混合的能量，甲酰胺的OPLS / AA-mod模型与其他模型相比，在质量上有不同的表现。因此，该模型得出的结果是负的，而其他模型则综合考虑了所有三个水模型的结果的正能量。实验数据支持后一种行为。尽管混合的亥姆霍兹自由能在整个组成范围内始终为负，但大多数测试模型组合显示出有限的混溶性，或至少非常接近某些组合物的混溶性极限。关于这些模型组合的可混溶性和混合能量，我们建议在水-甲酰胺混合物的模拟中使用CHARMM甲酰胺和TIP4P水模型的组合。
8. Liquid-Vapor Phase Transition: Thermomechanical Theory, Entropy Stable Numerical Formulation, and Boiling Simulations. [R] . Liu, J., Landis, C. M., Gomez, H., 2015

机译：液 - 气相变：热机械理论，熵稳定数值公式和沸腾模拟。

Free energy and entropy of a dipolar liquid by computer simulations

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