Department of Physics, National University of Defense Technology, Changsha 410073, People's Republic of China.
J Chem Phys. 2010 Jul 7;133(1):014302. doi: 10.1063/1.3462278.
The structure and vibrational spectra of (H(2)O)(n) (n=2-5) clusters have been studied based on first-principles molecular dynamics simulations. Trends of the cluster structures with the cluster size show that water molecules in cluster are bound more tightly. The vibrational spectra as a function of cluster size and temperature are obtained using Fourier transformation of the velocity autocorrelation function. Results of the clusters in ground state show that when the cluster size increases, the librational peaks shift to blue and the bonded intramolecular OH stretching bands shift to red due to the clusterization and hydrogen-bond strengthening. Meanwhile, there are no significant shifts in the intramolecular bending and free OH stretching modes, indicating that the free hydrogen atoms are insensitive to the local bonding environment. The temperature-dependent vibrational spectra, which exhibit similar behaviors from the dimer to pentamer, show that there are significant broadenings of the spectra with temperature caused by thermal motions. Moreover, different bands shift to different directions, where librational bands shift to red while bonded OH stretching bands shift to blue, although the blueshifts are quite small for the dimer and trimer.
基于第一性原理分子动力学模拟，研究了（H(2)O)(n)（n=2-5）团簇的结构和振动光谱。随着团簇尺寸的变化，团簇结构的趋势表明水分子在团簇中结合得更紧密。通过速度自相关函数的傅里叶变换得到了振动光谱作为团簇尺寸和温度的函数。基态团簇的结果表明，随着团簇尺寸的增加，由于团簇化和氢键增强，旋转峰蓝移，键合的内分子 OH 伸缩带红移。同时，内分子弯曲和游离 OH 伸缩模式没有明显的位移，表明游离氢原子对外界键合环境不敏感。与二聚体到五聚体相似的温度相关振动光谱表明，由于热运动，光谱随温度显著展宽。此外，不同的带向不同的方向移动，其中旋转带红移，而键 OH 伸缩带蓝移，尽管二聚体和三聚体的蓝移很小。
