CH-Stretching Vibrational Trends in Natural Gas Hydrates Studied by Quantum-Chemical Computations

Liu, Yuan; Ojamäe, Lars

doi:10.1021/acs.jpcc.5b01903

Cited by 23 publications

(35 citation statements)

References 61 publications

(181 reference statements)

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“…In Figure 6, the IR spectra of stretching vibrations in 16 different isomers of ice Ih are shown in the range of 3090 -3460 cm -1 . Unlike the distinct distribution of the sub-spectra of each proton group in water clusters, 75,77 the sub-spectra in ice overlap in all the 16 cases. This is also observed for the Raman spectra, shown in Figure 7.…”

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confidence: 80%

“…No obvious difference between ice Ih and XI is found for the OH stretching part of the spectrum, which might suggest that the intramolecular vibrations are little affected by the proton-ordering. Figure S6) as in previous studies, [75][76][77][78] and the contribution from each group to the total spectra was projected out (in accordance with the number of H atoms of the group and their vibrational amplitudes squared [75][76][77][78] ). In Figure 6, the IR spectra of stretching vibrations in 16 different isomers of ice Ih are shown in the range of 3090 -3460 cm -1 .…”

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confidence: 98%

“…In addition, the OH stretching vibrations are projected into different categories based on the contributions from different H-bond configurations as in previous studies. [75][76][77][78]  RESULTS AND DISCUSSION Assessment of DFT Methods. H-bonding between water molecules is the dominating interaction in ice.…”

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confidence: 99%

“…This is also observed for the Raman spectra, shown in Figure 7. The OH stretching vibration is very sensitive to the strength of the H-bond 75,77 (the Badger-Bauer rule). [94][95][96] We see that in ice each of the H-bonded pair configuration essentially contributes to all the peaks in the OH stretching region.…”

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Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods

Liu

Ojamäe

2016

J. Phys. Chem. B

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IR and Raman spectroscopic technology can be directly used to identify the occurrence of ferroelectric ice XI in laboratory or extraterrestrial settings. The performance of 16 different DFT methods applied on the ice Ih, VIII, IX, and XI crystal phases is evaluated. Based on a selected DFT computational scheme, the IR and Raman spectra of ice Ih and XI are derived and compared. When the spectra, both IR and Raman, of ice Ih and ice XI are compared, the librational vibrations are found to be the most affected by the proton ordering. The spectroscopic fingerprint of ice XI can be used to distinguish ferroelectric ice XI from ice Ih in the universe. Furthermore, the existence of only one kind of H-bond in ice Ih is demonstrated from the overlapping subspectra for different types of H-bonded pair configurations in 16 isomers of ice Ih, which provides an illustration to the historic debate on whether one or two kinds of H-bonds existed in ice.

Funding agencies: Swedish Research Council (VR); Swedish Supercomputer Center (SNIC/NSC); State Scholarship Fund of China Scholarship Council [201206060016]

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confidence: 98%

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confidence: 99%

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Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods

Liu

Ojamäe

2016

J. Phys. Chem. B

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Funding agencies: Swedish Research Council (VR); Swedish Supercomputer Center (SNIC/NSC); State Scholarship Fund of China Scholarship Council [201206060016]

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“…In this thesis H-bonded systems (natural gas hydrates, [1][2][3] water clusters, 4 and crystal ice 5 ) are studied by density functional theory (DFT) computations.…”

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Theoretical Studies of Natural Gas Hydrates and H-bonded Clusters and Crystals

Liu¹

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In this thesis H-bonded systems (natural gas hydrates, water clusters, and crystal ice) are studied by density functional theory (DFT) computations.Natural gas hydrates (NGHs) play an important role in energy and environmental fields: NGHs are considered as a promising backup energy resource in the near-future due to their tremendous carbon content; improper exploration of NGHs could induce geological disasters and aggravate the greenhouse effect. In addition, many technologies based on gas hydrates are being applied and developed. The thermodynamic stabilities of various water cavities in different clathrate crystalline phases occupied by hydrocarbon gas molecules are studied by dispersion-corrected hybrid functionals. The Raman spectra of C-C and C-H stretching vibrations of hydrocarbon molecules in various water cavities in the solid state are derived. The trends of C-H stretching vibrational frequencies are found to follow the prediction by the "loose cage ─ tight cage" model. In addition, the trends and origins of 13 C NMR chemical shifts of hydrocarbon molecules in various NGHs are presented. These theoretical results will enlarge the database of C-C and C-H stretching vibrational frequencies and 13 C NMR parameters of hydrocarbon molecules in NGHs, and provide valuable information to help identify the types of clathrate phases and varieties of guest molecules included in NGHs samples taken from natural sites.The behavior of water clusters may help to understand the properties of its liquid and solid states. The thermodynamic stabilities and IR spectra of a small-, medium-, and large-sized water cluster are studied in this work. After full optimization of (H 2 O) 20,54,100 using the hybrid functional B3LYP, the electronic energies, zero-point energies, internal energies, enthalpies, entropies, and Gibbs free energies of the water clusters are computed. The OH stretching vibrational IR spectra of (H 2 O) 20,54,100 are also presented and split into sub-spectra for different H-bond types based on the specific contributions from each group. It is found that the OH stretching vibrational frequencies of water are sensitive to the conformations of the H-bonds and the vibrations of the H-bonds belonging to different types are located in separated regions in the IR spectra. Thus, the spectroscopic fingerprints will reflect the H-bond topology of the water molecules in a water cluster.Ice XI has been suggested to be involved in the process of planetary formation as a considerable electric field might be formed from the ferroelectric ice XI in space. IR and Raman spectroscopic technology can be directly used to identify the occurrence of ferroelectric ice XI in laboratory or extraterrestrial settings. Due to the difficulty for DFT to describe non-covalent systems, the performance of 16 different DFT methods applied on the ice Ih, VIII, IX, and XI crystal phases are assessed. Based on the computational accuracy and cost, the II IR and Raman spectra of ice Ih and XI are derived and compared. The librational vib...

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IRandRaman Spectroscopy of Clathrate Hydrates

Uchida

Sum

2022

Clathrate Hydrates

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CH-Stretching Vibrational Trends in Natural Gas Hydrates Studied by Quantum-Chemical Computations

Cited by 23 publications

References 61 publications

Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods

Raman and IR Spectra of Ice Ih and Ice XI with an Assessment of DFT Methods

Theoretical Studies of Natural Gas Hydrates and H-bonded Clusters and Crystals

IRandRaman Spectroscopy of Clathrate Hydrates

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