School of Space Science and Physics, Shandong University, Weihai, 264209, China.
Molecules. 2019 Aug 27;24(17):3115. doi: 10.3390/molecules24173115.
It is always difficult to assign the peaks of a vibrational spectrum in the far-infrared region. The two distinct peaks seen in many ice phases are still a mystery to date. The normal modes of ice XV were calculated using the CASTEP code based on first-principles density functional theory. On the basis of vibrational modes analysis, we divided the translational modes into three categories: four-bond vibrations, which have the highest energy levels; two-bond vibrations, which have medium levels of energy; and relative vibrations between two sublattices, which have the lowest energy. Whale et al. found that some intramolecular stretching modes include the isolated vibration of only one O-H bond, whereas the others do not vibrate in ice XV. We verified this phenomenon in this study and attributed it to local tetrahedral deformation. Analysis of normal modes, especially in the translation and stretching band of ice XV, clarified the physical insights of the vibrational spectrum and can be used with other ice phases.
远红外区域的振动光谱峰的分配一直是困难的。在许多冰相中看到的两个明显的峰至今仍是一个谜。冰 XV 的正则模式是使用 CASTEP 代码基于第一性原理密度泛函理论计算的。基于振动模式分析，我们将平移模式分为三类：四键振动，具有最高能级；两键振动，具有中等能级；和两个子晶格之间的相对振动，具有最低能级。Whale 等人发现，一些分子内伸缩模式包括只有一个 O-H 键的孤立振动，而其他振动在冰 XV 中不振动。我们在这项研究中验证了这一现象，并将其归因于局部四面体变形。对正则模式的分析，特别是在冰 XV 的平移和伸缩带，澄清了振动光谱的物理见解，并可与其他冰相一起使用。
