Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods

IR and Raman spectroscopic
technology can be directly used to identify
the occurrence of ferroelectric ice XI in laboratory or extraterrestrial
settings. The performance of 16 different DFT methods applied on the
ice Ih, VIII, IX, and XI crystal phases is evaluated. Based on a selected
DFT computational scheme, the IR and Raman spectra of ice Ih and XI
are derived and compared. When the spectra, both IR and Raman, of
ice Ih and ice XI are compared, the librational vibrations are found
to be the most affected by the proton ordering. The spectroscopic
fingerprint of ice XI can be used to distinguish ferroelectric ice
XI from ice Ih in the universe. Furthermore, the existence of only
one kind of H-bond in ice Ih is demonstrated from the overlapping
subspectra for different types of H-bonded pair configurations in
16 isomers of ice Ih, which provides an illustration to the historic
debate on whether one or two kinds of H-bonds existed in ice.

红外（IR）与拉曼（Raman）光谱技术可直接用于实验室或地外环境中铁电冰XI（ferroelectric ice XI）的识别与检出。本研究评估了16种不同密度泛函理论（Density Functional Theory, DFT）方法在冰Ih、VIII、IX及XI晶相中的应用表现。基于优选的DFT计算方案，推导得到并对比了冰Ih与冰XI的红外及拉曼光谱。对比二者的红外与拉曼光谱后发现，摇摆振动受质子有序化的影响最为显著。冰XI的光谱指纹可用于在宇宙环境中区分铁电冰XI与冰Ih。此外，通过对冰Ih的16种异构体中不同氢键（Hydrogen Bond, H-bond）合对构型的重叠子光谱分析，证实冰Ih中仅存在单一类型的氢键，这为学界长期以来关于冰中存在一种还是两种氢键的历史性争论提供了实证阐释。