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Electronic state of small and large cavities for methane hydrate
Author(s) -
Ida T.,
Mizuno M.,
Endo K.
Publication year - 2002
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10095
Subject(s) - methane , hydrate , molecule , hydrogen bond , chemistry , bond length , hydrogen , clathrate hydrate , proton , ab initio , cluster (spacecraft) , ab initio quantum chemistry methods , crystallography , computational chemistry , organic chemistry , physics , quantum mechanics , computer science , programming language
It is well known that methane hydrate is aggregates of small and large hydrogen bonded water cavities (composed of 12 pentagonal faces of 20 water molecules, and 12 pentagonal and two hexagonal faces of 24 water molecules, respectively) where one methane molecule is encaged. We calculated the methane molecule in vacuum, the small and large cavities by ab initio MO method to clarify the electronic state. The proton of methane in the cavities is shown to form the weak hydrogen bond (O…H—C) between methane and four water molecules, and the H‐bond lengths and energies in the small and large cavities were estimated as (0.293 nm, 6.8 kJ/mol) and (0.309 nm, 5.2 kJ/mol), respectively. The calculated values of symmetric C—H stretching frequencies and 13 C‐NMR chemical shieldings of the methane in the two cluster cavities show good agreement with the experimental ones observed by Sum et al. and Ripmeester and coworker, respectively. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1071–1075, 2002