Abstract-Theoretical Study on Electronic and Vibrational Properties of Hydrogen Bonds in Glycine-Water Clusters

• Yulei Shi^a, 
• Zhiyuan Zhang^b, c, 
• Wanrun Jiang^b, c, 
• Zhigang Wang^b, c, , , 

• ^a Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048, China.
• ^b Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
• ^c Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012, China

http://www.sciencedirect.com/science/article/pii/S000926141730578X

The hydrogen bond (H-bond) in organic-water molecules is essential in nature, and it present unique properties distinct from those in pure water or organic clusters. Combining with the charge-transfer and energy decomposition analyses, we investigated the penetrating molecular-orbitals in glycine-water clusters, which give evidences of the covalent-like characteristics of H-bonds in this system. Besides, the infrared spectral features provide a rare opportunity to discover the exceedingly-evident redshifts of symmetric stretching modes (Symst) in water on forming H-bond, in contrast to the slightly-redshifted asymmetric stretching modes (Asyst) in water. To explain these intriguing behaviors, we further analyzed the nuclear vibrating patterns, which clearly reveal that H-bond retains two unexpected effects on nuclear motions in water: i) Intensifying donor Symst, and ii) Inhibiting donor Asyst. Furthermore, we also quantified the impact of anharmonic quantum fluctuations on each hydrogen bond. For the stretching modes involved in H-bonds, red shifts up to more than one hundred wave numbers are observed under anharmonic vibration, explicitly indicating the increased “covalency” of H-bonds. These finds shed light on the essential understanding of H-bonding comprehensively, and should provide incentives for future experimental studies