Department of Chemistry, University of North Dakota , Grand Forks, North Dakota 58202, United States.
J Phys Chem B. 2014 Mar 20;118(11):3175-82. doi: 10.1021/jp500577t. Epub 2014 Mar 7.
We present molecular simulation results on the thermodynamics of phase transitions (specifically, the vapor-liquid and metal-nonmetal transitions) in mercury, as predicted by effective potential models. We use a recently developed method, known as Expanded Wang-Landau simulations, to determine the grand-canonical partition function of systems of mercury atoms. Using the statistical mechanics formalism, we are then able to determine all thermodynamic properties of the system, including the Gibbs free energy and entropy. Prior experimental and theoretical work has emphasized the strong interplay between the vapor-liquid coexistence and the metal-nonmetal transition. We therefore start by assessing the accuracy of the effective potentials considered in this work through a comparison to the available experimental data. We then analyze the thermodynamics of the nonmetal liquid-metal liquid transition, characterized by sharp variations in the rate of change of Gibbs free energy and enthalpy as a function of density. We also identify a crossover density (10.5 g/cm(3)) consistent with the results of recent ab initio calculations and with the experiment.
我们展示了有效势能模型预测的汞的相变（特别是汽-液和金属-非金属转变）热力学的分子模拟结果。我们使用了一种最近开发的方法，称为扩展的 Wang-Landau 模拟，来确定汞原子系统的巨正则配分函数。然后，我们可以使用统计力学形式来确定系统的所有热力学性质，包括吉布斯自由能和熵。先前的实验和理论工作强调了汽-液共存和金属-非金属转变之间的强烈相互作用。因此，我们首先通过与现有实验数据的比较来评估本工作中所考虑的有效势能的准确性。然后，我们分析了非晶态-液态金属转变的热力学性质，其特征是吉布斯自由能和焓随密度变化的变化率发生急剧变化。我们还确定了一个交叉密度（10.5 g/cm3），与最近的从头计算结果和实验结果一致。
