Belosludov Vladimir, Gets Kirill, Zhdanov Ravil, Malinovsky Valery, Bozhko Yulia, Belosludov Rodion, Surovtsev Nikolay, Subbotin Oleg, Kawazoe Yoshiyuki
Department of Physics, Novosibirsk State University, 630090, Novosibirsk, Russia.
Nikolaev Institute of Inorganic Chemistry SB RAS, 630090, Novosibirsk, Russia.
Sci Rep. 2020 Apr 30;10(1):7323. doi: 10.1038/s41598-020-64210-1.
A method for studying the time dependence of the short-range molecular order of water has been proposed. In the present study, water is considered as a dynamic network between molecules at distances not exceeding 3.2 Å. The instantaneous configurations obtained with the molecular dynamics method have been sequentially analyzed. The mutual orientation of each molecule with its neighboring molecules has been studied and the interaction energy of each pair of neighbor molecules has been calculated. The majority of mutual orientation angles between molecules lie in the interval [0°; 20°]. More than 85% of the molecular pairs in each instantaneous configuration form H-bonds and the H-bond network includes all water molecules in the temperature range 233-293 K. The number of H-bonds fluctuates near the mean value and increases with decreasing temperature, and the energy of the vast majority of such bonds is much higher than the thermal energy. The interaction energy of 80% of the H-bonding molecular pairs lies in the interval [-7; -4] kcal/mol. The interaction energy of pairs that do not satisfy the H-bond angle criterion lies in the interval [-5; 4] kcal/mol; the number of such bonds does not exceed 15% and decreases with decreasing temperature. For the first time it has been found that in each instantaneous configuration the H-bond network contains built-in nanometric structural heterogeneities formed by shorter H-bonds. The fraction of molecules involved in the structural heterogeneities increases from 40% to 60% with a temperature decrease from 293 K to 233 K. Each heterogeneity has a finite lifetime and changeable structure, but they are constantly present during the entire simulation time.
提出了一种研究水的短程分子有序性时间依赖性的方法。在本研究中，水被视为分子间距离不超过3.2 Å的动态网络。已对通过分子动力学方法获得的瞬时构型进行了顺序分析。研究了每个分子与其相邻分子的相互取向，并计算了每对相邻分子的相互作用能。分子间的大多数相互取向角位于[0°; 20°]区间内。在每个瞬时构型中，超过85%的分子对形成氢键，并且氢键网络在233 - 293 K的温度范围内包含所有水分子。氢键的数量在平均值附近波动，并随温度降低而增加，并且绝大多数此类键的能量远高于热能。80%的氢键分子对的相互作用能位于[-7; -4] kcal/mol区间内。不满足氢键角标准的分子对的相互作用能位于[-5; 4] kcal/mol区间内；此类键的数量不超过15%，并随温度降低而减少。首次发现，在每个瞬时构型中，氢键网络包含由较短氢键形成的内置纳米级结构异质性。随着温度从293 K降至233 K，参与结构异质性的分子比例从40%增加到60%。每个异质性都有有限的寿命和可变的结构，但在整个模拟时间内它们始终存在。
