甘油对冰晶生长抑制作用的分子动力学模拟

Inhibitory Mechanism of Glycerol on the Growth of Ice Crystals by Molecular Dynamics

采用分子模拟方法研究了正交晶系冰晶(020)生长面在不同浓度甘油水溶液中的生长情况.通过统计分析氢键数、密度分布函数、均方根偏差和原子间径向分布函数研究了水分子和甘油分子的动态行为.结果表明,甘油分子在水溶液中可与水分子形成大量氢键,这使水分子间的氢键作用受到抑制,降低了水分子的扩散性,致使冰晶不易成核和生长;另外,一些甘油分子可代替水分子吸附在晶面上,甚至占据晶格位点,这种行为打破了冰晶的对称性并且降低了冰晶的生长速率.因此,甘油可同时在晶面和液相中抑制冰晶的生长.

The molecular simulations of the growth process of crystal face(020)of orthorhombic ice were performed in glycerol aqueous solutions at 225 K,1×105 Pa in order to investigate the inhibitory mechanism of glycerol for ice growth.Hydrogen bond number,density profile,root mean square deviation and intermolecular radial distribution functions were calculated to study the dynamic behavior of water and glycerol molecules.The result shows that the glycerol molecules can form numerous hydrogen bonds with water molecules.And water-water hydrogen bonds decreased with the increasing concentration of glycerol.Glycerol inhibits the interaction of hydrogen bonding between water molecules and makes nucleation of ice crystal difficult.Glycerol increases the viscosity of water solution and decreases the diffusivity of water molecule from solution to ice crystal face.More important,glycerol molecules have a competitive adsorption with water molecules on the crystal face,even occupy the surface lattice site and take place two or three water molecules.This behavior can break the symmetry of ice crystal face and prevent the further growth.Therefore,glycerol can play a role in inhibiting the growth of ice crystals in both aqueous solution and crystal face.So,the current research gives a better understanding for the inhibitory mechanism of glycerol on the growth of ice crystal and provide theoretical support for optimizing the protection prescriptions of biological tissues and protein medicine.