Karmakar Anwesa, Chandra Amalendu
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
J Chem Phys. 2015 Apr 28;142(16):164505. doi: 10.1063/1.4918579.
First principles theoretical studies of vibrational spectral diffusion of the stretch modes of water and azide (N3(-)) ions are presented by means of ab initio molecular dynamics simulations for two different concentrations of the ions. The vibrational spectral diffusion of hydration shell water in a dilute solution containing a single azide ion is found to occur with three time scales while two time scales are found for the spectral diffusion in the solution of higher ion concentration. The frequency time correlation of the stretching vibration of azide ion is also found to have two time scales. The vibrational spectral diffusion of the stretching mode of azide ions in the concentrated solution is found to occur at a slightly faster rate while that of the water OD modes becomes slower with increase of ion concentration. The effects of dispersion interactions are also investigated by using a dispersion corrected density functional. The time constants of frequency correlations and dynamical spectral shifts are analyzed in terms of the relaxation of azide ion-water and water-water hydrogen bonds. The results of present theoretical calculations are compared with the available experimental and other theoretical results.
通过从头算分子动力学模拟，针对两种不同离子浓度，给出了水和叠氮化物（N3(-)）离子伸缩模式振动光谱扩散的第一性原理理论研究。发现在含有单个叠氮离子的稀溶液中，水合壳层水的振动光谱扩散以三个时间尺度发生，而在较高离子浓度的溶液中光谱扩散则有两个时间尺度。还发现叠氮离子伸缩振动的频率时间相关性也有两个时间尺度。发现在浓溶液中叠氮离子伸缩模式的振动光谱扩散发生速率稍快，而水的OD模式的振动光谱扩散随离子浓度增加而变慢。还使用色散校正密度泛函研究了色散相互作用的影响。根据叠氮离子 - 水和水 - 水氢键的弛豫情况，分析了频率相关性和动态光谱位移的时间常数。将当前理论计算结果与现有的实验结果及其他理论结果进行了比较。
