Since neutron scattering experiments in the 1990’s revealed two peaks of hydrogen bonding in ice crystal, theoretical modeling for this issue remains to be a challenging problem. J. C. Li and K. D. Ross introduced a model positing two types of hydrogen bond strength to explain the observed splitting in the vibration spectra [J. C. Li and K. D. Ross, Nature (London), 365, 327-329 (1993)]. However, this hypothesis was controversial from its inception and has not been widely accepted thus far: Recently, computational simulations by Dr. Zhang Peng, Associate Professor from the School of Space Science and Physics at Shandong University (Weihai) clarified this issue for the first time and proposed a new explanation.
Zhang and his research team investigated the impact of hydrogen bond of pairwise H2O configurations and found that different proton arrangements of pairwise H2O in an ice crystal lattice could not alter the nature of hydrogen bonding as significantly as suggested by the Li-Ross model. They computationally constructed a special geometrical structure with only contain strong or weak hydrogen bond strength in the ice crystal lattice according to the Li-Ross model and performed ab initio calculations to demonstrate that the model is incorrect. According to the phonon density of states (PDOS) with different bond lengths, they observed that the intramolecular O-H stretching vibration modes produce energy level splitting that strongly correlates with the double peaks of hydrogen bonds.
Their work provides evidence that intermolecular hydrogen bond splitting may be attributed to coupling between the internal covalent vibrations, where a stronger intramolecular O-H bond links with a weaker intermolecular hydrogen bond, or vice versa. The current computational work is expected to shed new light on the nature of the hydrogen bonds in water, and offer a new approach to probing the interaction between water and biomaterials in which hydrogen bonding is essential.
Related results have been published in the Journal of Chemical Physics (DOI: 10.1063/1.4736853) and RSC Advances (DOI: 10.1039/C3RA40317C). Xiao He et al., a research team from University of Illinois at Urbana-Champaign, USA, cited this work and presented embedded-fragment approach to mutually confirmed Zhang’s conclusions (DOI: 10.1063/1.4767898). Another research team, Tian Linan et al, from the University of Manchester, UK, performing simulations based on high pressure ice also replicated these results (DOI: 10.1063/1.4767718). This work is supported by the National Natural Science Foundation of China (Grant No. 11075094).
Source: SDU at Weihai