Zero-point fluctuation of hydrogen bond in water dimer from ab initio molecular dynamics

• Published in: Chinese physics B 2020-10, Vol.29 (10), p.103101
• Main Authors: Jiang, Wan-Run, Wang, Rui, Ren, Xue-Guang, Zhang, Zhi-Yuan, Li, Dan-Hui, Wang, Zhi-Gang
• Format: Article
• Language: English
• ISSN: 1674-1056
• DOI: 10.1088/1674-1056/abab6d

Dynamic nature of hydrogen bond (H-bond) is central in molecular science of substance transportation, energy transfer, and phase transition in H-bonding networks diversely expressed as solution, crystal, and interfacial systems, thus attracting the state-of-the-art revealing of its phenomenological edges and sophisticated causes. However, the current understanding of the ground-state fluctuation from zero-point vibration (ZPV) lacks a firm quasi-classical base, concerning three basic dimensions as geometry, electronic structure, and interaction energy. Here, based on the ab initio molecular dynamics simulation of a ground-state water dimer, temporally separated fluctuation features in the elementary H-bond as the long-time weakening and the minor short-time strengthening are respectively assigned to two low-frequency intermolecular ZPV modes and two O–H stretching ones. Geometrically, the former modes instantaneously lengthen H-bond up to 0.2 Å whose time-averaged effect coverages to about 0.03 Å over 1-picosecond. Electronic-structure fluctuation crosses criteria’ borders, dividing into partially covalent and noncovalent H-bonding established for equilibrium models, with a 370% amplitude and the district trend in interaction energy fluctuation compared with conventional dragging models using frozen monomers. Extended physical picture within the normal-mode disclosure further approaches to the dynamic nature of H-bond and better supports the upper-building explorations towards ultrafast and mode-specific manipulation.