Molecular Dynamics Simulation on Microscopic Characteristics of Carbon Dioxide in Trans-Critical Progress
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摘要: 应用分子动力学模拟方法研究了跨越临界点时二氧化碳体系微观结构特性。径向分布函数的分析表明，临界点前后体系内短程序结构变化很小，主要受分子间极强的近邻相互作用的强化效果影响，第一近邻配位数的分析进一步显示近程结构的变化以配对分子数量的变化为主；气态条件下的二氧化碳体系仍呈“近程有序且长程无序”状态；静态结构因子的分析表明，拟临界区体系中存在中远程有序结构；定义了无序距离，该参数的突增表明了临界点附近分子间相互作用距离剧烈增大。Abstract: Molecular dynamics (MD) simulations was performed to analyze the microscopic characteristics of carbon dioxide in trans-critical progress. Radial distribution function (RDF) analysis exhibited that the short-range structure varied weakly near the critical point, which was mainly enhanced by the strong neighbor intermolecular interaction. The simulation results of the coordination number in first shell further show that the variation of short-range structure primarily lies in the number change of coordinated molecular; The gaseous CO2 is still of an ordered structure in the short-range and of a disordered structure in the long-range; The static structure factor analysis showed the existence of medium/long-rang ordered structure. Disorder range was defined and its abrupt surge showed explicitly that the range of intermolecular interaction increased in the pseudo-critical region.
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图 6 T=300~304.13 K时C-C原子间RDF对比
Figure 6. Comparison of C-C Pair RDF when T=300~304.13 K
图 7 T=304.13~308 K时 C-C原子间RDF对比
Figure 7. Comparison of C-C pair RDF when T=304.13~308 K
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