水玻璃化过程的氢键结构特性

为了解玻璃化过程氢键结构特性,采用分子模拟的手段计算了三种压力下的水玻璃化过程氢键的角度、距离、生命期和数量.计算结果显示:(i)氢键角度呈现泊松分布的特征,随着温度降低分布氢键角度分布范围变窄,峰值变高,在0～13°范围,随温度降低,分布数值变大;而在大于13°,随温度降低,分布数值变小;(ii)氢键距离也呈现泊松分...

PROPERTIES OF HYDROGEN BONDS OF WATER DURING VITRIFICATION

For the purpose of understanding properties of hydrogen bonds during vitrification,molecular simulations were carried to calculate hydrogen bonds for water cooled under three pressures.We have calculated hydrogen bond life distributions.The results show :(ⅰ)hydrogen bond angles distribute in a way similar to Poisson distribution,and as temperature drop,distributing range become narrower,peak become higher,values of distribution become higher when hydrogen bond angles is in the region between 0 and 13°,but lower when hydrogen bond angles >13°,(ⅱ) hydrogen bond distances also distribute in a way similar to Poisson distribution,and as temperature drop,distributing range become narrower,peak become higher,values of distribution become higher when hydrogen bond angles is in the region between 0.15 and 0.18 nm,but lower when hydrogen bond angles are in 0.18 ~0.27 nm,(ⅲ) hydrogen bond life distribute in a way similar to power or exponential functions in which independent variable is multiplied by a negative factor,and with temperatures dropping,both the range and the values of life distribution show significant differences,(ⅳ) pressure has weak effects on the trend of life distributions,but oscillations of life distribution curves show differences when temperatures is below a temperature,leading to significant differences of average life at different pressures,(ⅴ) the total number of hydrogen bonds and average hydrogen bonds number of each H2O both increase as temperature drop.During vitrifying process,completely free water portion get low,portion of water molecules with four hydrogen bonds forming tetrahedron get high dramatically from 290 K to 260 K,then shows little change,and portions of those with one,two,or three hydrogen bonds show a overall tendency to get higher as temperature decrease.f4 is much less than f1,f2,f3,showing extremly low degree of crystallization.