Structures and Hydrogen Bonding Interactions in Urea-water System Studied by All-atom MD Simulation and Chemical Shifts in NMR Spectrum

采用分子动力学模拟方法结合核磁共振化学位移和粘度对尿素水溶液在稀浓度范围内的结构和弱相互作用进行研究. 从径向分布函数(RDF)分析看出，尿素水溶液中存在着几种不同类型、不同氢键形成能力的传统氢键. 氢键网络分析发现尿素水溶液体系在水富集区域，水分子倾向于自身缔合形成稳定的分子簇结构，而随着尿素浓度的逐渐增加，水的有序结构受到破坏，水分子和尿素分子发生了交叉缔合作用形成氢键，尿素分子有形成自身缔合的趋势. 分子动力学统计的平均氢键数与核磁共振化学位移和粘度数据结果进行比较，发现它们的变化趋势一致，证明了实验和理论结果有很强的可靠性.

Structures and Hydrogen Bonding Interactions in Urea-water System Studied by All-atom MD Simulation and Chemical Shifts in NMR Spectrum

The interactions and structures of the urea-water system are studied by an all-atom molec-ular dynamics (MD) simulation. The hydrogen-bonding network and the radial distribution functions are adopted in MD simulations. The structures of urea-water mixtures can be classified into different regions from the analysis of the hydrogen-bonding network. The urea molecule shows the certain tendency to the self-aggregate with the mole fraction of urea increasing.Moreover,the results of the MD simulations are also compare with the chemical shifts and viscosities of the urea aqueous solutions, and the statistical results of the average number hydrogen bonds in the MD simulations are in agreement with the experiment data such as chemical shifts of the hydrogen atom and viscosity.