论文标题
从增强采样分子动力学模拟的液态水和六角冰的相平衡
Phase equilibrium of liquid water and hexagonal ice from enhanced sampling molecular dynamics simulations
论文作者
论文摘要
我们使用增强的采样分子动力学模拟研究了由TIP4P/ICE间原子势建模的液态水和冰IH之间的相平衡。我们的方法基于冰IH-liquid自由能的计算，这些模拟访问这两个阶段的模拟。可逆互转换是通过引入静态偏置电位作为顺序参数的函数来实现的。定制阶参数以结晶冰IH中氧的六角形钻石结构。我们分析了系统大小对冰IH液体自由能差的影响，并在热力学极限下获得了270 K的熔化温度。该结果与热力学整合（272 K）和共存模拟（270 K）的估计相一致。由于顺序参数不包括有关质子坐标的信息，因此自发形成的固体构型包含质子疾病，如ICE IH所期望的。
We study the phase equilibrium between liquid water and ice Ih modeled by the TIP4P/Ice interatomic potential using enhanced sampling molecular dynamics simulations. Our approach is based on the calculation of ice Ih-liquid free energy differences from simulations that visit reversibly both phases. The reversible interconversion is achieved by introducing a static bias potential as a function of an order parameter. The order parameter was tailored to crystallize the hexagonal diamond structure of oxygen in ice Ih. We analyze the effect of the system size on the ice Ih-liquid free energy differences and we obtain a melting temperature of 270 K in the thermodynamic limit. This result is in agreement with estimates from thermodynamic integration (272 K) and coexistence simulations (270 K). Since the order parameter does not include information about the coordinates of the protons, the spontaneously formed solid configurations contain proton disorder as expected for ice Ih.
