Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
J Chem Phys. 2013 Sep 21;139(11):114705. doi: 10.1063/1.4821455.
Stockmayer fluids are a prototype model system for dipolar fluids. We have computed the freezing temperatures of Stockmayer fluids at zero pressure using three different molecular-dynamics simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature two-phase coexistence method, and the constant-pressure and constant-enthalpy two-phase coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with the dimensionless dipole moment μ*=1, √2, √3 is 0.656 ± 0.001, 0.726 ± 0.002, and 0.835 ± 0.005, respectively. The freezing temperature increases with the dipolar strength. Moreover, for the first time, the solid-liquid interfacial free energies γ of the fcc (111), (110), and (100) interfaces are computed using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, i.e., γ100 > γ110 > γ111.
Stockmayer 流体是偶极流体的原型模型体系。我们使用三种不同的分子动力学模拟方法，即过冷-过热法、等压-恒温两相共存法和等压-等焓两相共存法，计算了零压下 Stockmayer 流体的冻结温度。Stockmayer（SM）流体无量纲偶极矩μ*=1、√2、√3 的冻结温度（以约化单位表示）的最佳估计值分别为 0.656±0.001、0.726±0.002 和 0.835±0.005。冻结温度随偶极力的增加而增加。此外，我们首次使用两种独立的方法，即劈开壁方法和界面涨落方法，计算了 fcc（111）、（110）和（100）界面的固-液界面自由能γ。这两种方法都表明界面自由能随偶极矩的增加而增加。尽管界面涨落方法表明界面各向异性较弱，特别是对于强偶极 SM 流体，但这两种方法都预测了界面各向异性的相同趋势，即γ100>γ110>γ111。
