Investigation of hydrogen bond vibrations of ice

Abstract

Despite its simple molecular structure, water is still a mystery to scientists. For the atomic and molecular vibrational modes of ice, as is well known, there are two kinds of vibrations: intra-molecular O—H stretching vibration and H—O—H bending vibration within the molecules and three kinds of molecular spatial rotations. However, thirty years ago, a high flux inelastic neutron scattering experiment showed that there are two distinct characteristic peaks in the far-infrared molecular translational vibration region of many ice phases. The origins of these peaks have not been determined till now. In this work, based on the CASTEP code, a first-principles density functional theory plane wave programme, the vibrational spectra as well as the vibrational normal modes of a series of ice phases are investigated. Two kinds of intrinsic hydrogen bond vibrational modes are first found in hydrogen-ordered ice Ic. Then it is found to be a general rule among ice family. Based on the ideal model, we prove that the two vibrational modes can be classified as four-bond vibration and two-bond vibration. There are many coupling modes in-between due to tetrahedral structure deformation under high pressure. Besides, there are also some optical vibrational modes with lower energy in the translational region, such as cluster vibrations and inter-plane vibrations. In Ice VII/VIII and XV/VI, each of which consists of two sublattices, there exist non-hydrogen bond vibrations. These molecular translational vibrations can explain all the far-infrared vibrational spectrum of ice phase, which makes up the last piece of the jigsaw puzzle for the molecular vibration theory of ice. The two vibrational modes do not exist in liquid water due to the collapse of the rigid tetrahedral structure. Thus, a window remains for ice resonance absorption with minimum energy loss in water. This theory is expected to be applicable to industrial deicing, food thawing, gas hydrate mining, and biomolecule frozen molding, etc.

Computational Analysis of Hydrogen Bond Vibrations of Ice III in the Far-Infrared Band

“…Then, we confirmed that the two distinct HB peaks in ice Ih originated from these two kinds of HB modes [19]. By now, we have investigated almost all the ice phases, thereby determining that this is a general rule for ice because of its local tetrahedral structure [18]. Based on these new findings, we have obtained a deeper understanding of the HB interactions in water ice and their broad role in nature.…”

“…The two intrinsic HB vibrational modes originate from the local tetrahedral geometry of the ice lattice. This finding has proved to be a general rule for the ice family [18]. For ice phases under atmospheric pressure, such as ices Ih, XI, and Ic, the two characteristic HB peaks can be easily explained by the existence of two kinds of HB vibrational modes.…”

“…We used the generalized gradient approximation to handle the complicated spatial distribution of electron density. The revised Perdew-Burke-Ernzerhof (RPBE) exchange-correlation functional was selected because it gives rise to the most satisfactory accuracy for the vibrational spectrum calculation of ice [18]. The energy threshold and self-consistent field tolerance were both set at 1 × 10 eV/atom for the geometry optimization.…”

“…Two kinds of intrinsic HB vibrational modes, denoted two-bond and four-bond modes, were found for the ideal ice Ic [21]. A series of investigations of the ice phases has revealed that this is a general rule for the ice family and may successfully explain their far-IR band [18][19][20]. In the present study, we theoretically analyzed the vibrational modes in the translation band to identify the characteristic HB vibrations of ice III in comparison with those of the H-ordered ice IX.…”

“…Since two distinct peaks in the far-infrared (IR) region of ice were first probed in the 1990s by inelastic neutron scattering (INS) experiments [15][16][17], the origin of these two vibrational peaks has remained a controversial issue [18][19][20]. Using first-principles density functional theory (DFT), we developed an approach to determine the lattice dynamic process of the crystal vibrational spectrum.…”