应用TIP7P水分子模型动力学模拟研究冰的熔点

Dynamic simulation of the melting point of ice using TIP7P water model

应用TIP7P水分子模型对真空中冰表面体系进行了动力学模拟,根据分子内能和晶格对称性的变化,确定了该水模型下冰的熔点为(237±1)K.研究表明,在恒温恒压下通过TIP7P模型模拟得到的冰的密度接近于实验值.冰在温度较低时保持了冰的Ih对称性,而温度较高时融化成了液态水.此外,研究发现即使在低温时,冰的表面也总是潮湿的,因为冰表面总有少量的冰融化成水.与冰内部不同的是,冰表面暴露在真空中进行恒温恒容模拟可以避免过热现象的发生,从而有利于准确判断冰的熔点.通过冰表面模拟和其熔点的估算,积累了TIP7P模型水的相图的经验.

Rigid TIP7P water model was applied to simulate ice surface exposed in vacuum.The melting point of(237±1)K was determined by detecting the changes in internal energy and lattice symmetry.Within the NPT simulations frame,TIP7P model gives the density close to experimental value,and the ice keeps in solid with Ih symmetry at low temperatures but melts into liquid at high temperatures.Even at low temperatures,the surface of ice is always wet due to pre-melting.Unlike bulk ice in NPT simulations,overheating never occurs in ice surface exposed in vacuum which makes for precise determination of melting point.Study on ice and its melting point using TIP7P model will be employed to depict the phase graph of water.