Computational assignments of lattice vibrations of ice Ic

Yuan, Zhenyu; Zhang, Peng; Yao, Shukai; Lu, Ying‐Bo; Yang, Haozhi; Luo, Huiwen; Zhao, Zeng-Ji

doi:10.1039/c7ra04332e

Cited by 22 publications

(48 citation statements)

References 48 publications

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“…Morrison and Jenkins [29] suggested that the splitting of the optical modes is due to the coupling with the intramolecular stretching vibrations. In our previous study, the existence of two basic H-bond vibrational modes was first established in ice Ic [30]. These two peaks are contributed by the two fundamental vibrations of H-bonds, the two-bond mode and the four-bond mode.…”

Section: Resultsmentioning

confidence: 90%

Computational analysis of vibrational spectrum and hydrogen bonds of ice XVII

Zhu

Yuan

et al. 2019

New J. Phys.

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Based on first-principles density functional theory, we investigated the relationship between the vibrational normal modes and the spectrum of the newest laboratory-prepared ice phase, an empty clathrate hydrate structure from gas hydrate named ice XVII. A 48-molecule supercell was designed to mimic the hydrogen-disordered structure. Despite its much lower density than ice Ih, its phonon density of states shows features very similar to those of that phase. In our previous studies of ice Ic and ice XIV, we found two basic hydrogen bond vibrational modes in these hydrogen-ordered ice phases, which contribute two sharp hydrogen bond peaks in the translation region. In this study, we found that this rule also holds in the hydrogen-disordered phase ice XVII. A water molecule vibrating along its angle bisector possesses strong energy, because this vibrational mode involves oscillation against four bonded neighbors. In contrast, a water molecule vibrating perpendicular to its angle bisector has low energy because this mode involves only two of the molecule's hydrogen bonds. This is an evidence in hydrogen-disordered ice and strengthens our proposal that the existence of two basic hydrogen bond vibrational modes is a general rule among ice family. Figure 5. Smoothed probability density distribution of bond angles of ice XVII (blue) and ice Ih (black). Inset: Normal mode at 1647 cm −1 . This vibrational mode is mainly contributed by water molecules with large bond angles, which are highlighted in gold.

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Section: Resultsmentioning

confidence: 90%

Computational analysis of vibrational spectrum and hydrogen bonds of ice XVII

Zhu

Yuan

et al. 2019

New J. Phys.

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“…The mechanism of H-bond vibrations was the central topic in our previous studies [25,26,27,28,29]. We found two basic H-bond vibration modes in ice Ic, which gave rise to two triangular peaks in INS [27]. In all ice phases, each water molecule is linked with four neighbors via H-bonds to form a tetrahedral structure.…”

Section: Resultsmentioning

confidence: 99%

“…Accordingly, the lengths of the H-bonds in ice XVI are bigger than Ih, manifesting an obvious red-shift of the H-bond (for the upmost mode, 314 cm −1 vs. 327 cm −1 ), and a slight blue-shift in the stretching region [25]. In the translational region, two H-bond peaks were found similar to the spectrum of ice Ic [27]. These H-bond vibrations could be classified into two groups based on their physical motions.…”

Section: Discussionmentioning

confidence: 99%

Investigations of the Hydrogen Bonds and Vibrational Spectra of Clathrate Ice XVI

Wang

Zhu

et al. 2019

Materials

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Natural gas hydrates are ice-like crystalline materials formed from natural gas and clathrate ice under high pressure and low temperature. Ice XVI, the first S-II type clathrate ice produced in the lab, was simulated by first-principles density functional theory with the CASTEP code. A 34-molecule supercell was built to mimic the hydrogen-disordered structure. The vibrational spectra were calculated as a reference for inelastic neutron scattering (INS), infrared (IR) absorption, and Raman scattering experiments. Two kinds of H-bond vibration modes corresponding to two different bond strengths were found in our previous studies. In this paper, the statistics of distribution calculated by integrating these two kinds of modes was found to match the phonon density of states (PDOS) very well. We confirmed that the two basic types of H-bonds also appeared in clathrate ice XVI. The typical normal modes were analyzed to illustrate the dynamic process of lattice vibrations.

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“…There are four H-bonds linked with one molecule to form a tetrahedral structure in ice crystals. For ice Ic, there are two kinds of vibration modes for one molecule: two H-bonds vibrating mode and four H-bonds vibrating mode with a strength ratio of

[ 33 ]. These two types of modes were also observed in the ice XIV crystal lattice.…”

Section: Resultsmentioning

confidence: 99%

DFT Simulations of the Vibrational Spectrum and Hydrogen Bonds of Ice XIV

Zhang

Wang

et al. 2018

Molecules

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It is always a difficult task to assign the peaks recorded from a vibrational spectrum. Herein, we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV that can be referenced as inelastic neutron scattering (INS), infrared (IR), and Raman experimental spectrum. The INS spectrum is proportional to the phonon density of states (PDOS) while the photon scattering signals reflect the normal vibration frequencies near the Brillouin zone (BZ) center. Based on good agreements with the experimental data, we identified the relative frequency and made scientific assignments through normal vibration modes analysis. The two hydrogen bond (H-bond) peaks among the ice phases from INS were discussed and the dynamic process of the H-bond vibrations was found to be classified into two basic modes. We deduced that two H-bond modes are a general rule among the ice family and more studies are ongoing to investigate this subject.

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Computational assignments of lattice vibrations of ice Ic

Abstract: Herein,viathe first-principles density functional theory, CASTEP code, we investigated the 15 vibrational normal modes of ferroelectric hydrogen-ordered phase of ice Ic and the two peaks of hydrogen bond are clarified.

Cited by 22 publications

References 48 publications

Computational analysis of vibrational spectrum and hydrogen bonds of ice XVII

Computational analysis of vibrational spectrum and hydrogen bonds of ice XVII

Investigations of the Hydrogen Bonds and Vibrational Spectra of Clathrate Ice XVI

DFT Simulations of the Vibrational Spectrum and Hydrogen Bonds of Ice XIV

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