Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (8): 1437-1446.doi: 10.3866/PKU.WHXB201405292

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Stability and Raman Spectroscopy of Alkane Guest Molecules (CnHm, n≤6, m≤14) in 51262 and 51264 Water Cavities by Density Functional Theory Calculations

CAO Xiao-Xiao1, SU Yan1, ZHAO Ji-Jun1, LIU Chang-Ling2,3, ZHOU Pan-Wang4   

  1. 1. Laboratory of Materials Modification by Laser, Ion and Electron Beams of the Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning Province, P. R. China;
    2. Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao 266071, Shandong Province, P. R. China;
    3. Qingdao Institute of Marine Geology, Qingdao 266071, Shandong Province, P. R. China;
    4. State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116024, Liaoning Province, P. R. China
  • Received:2014-04-21 Revised:2014-05-27 Published:2014-07-18
  • Contact: SU Yan E-mail:su.yan@dlut.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (11174045, 11304030) and Fundamental Research Funds for the Central Universities of China (DUT14LK19).

Abstract:

The gas composition in natural gas hydrate deposits is complex, and therefore the use of spectroscopic analysis to elucidate the chemical composition is of great significance. Using density functional theory (DFT) calculations at the B97-D/6-311++G(2d, 2p) level, we systematically explored the stability of 18 alkane guest molecules in two standard water cavities (51262 and 51264). The results indicated that most alkane guest molecules can be stored in the 51262 cage, with the exception of 3-methylpentane and 2,3-dimethylbutane, while all 18 alkanes can be encapsulated in the 51264 cage. The Raman spectroscopic characteristics of five straight-chain and four cyclic alkane guest molecules in the 51262 and 51264 cages were also simulated. The majority of the Raman bands of the straight-chain alkanes in the C―H stretching region were found to move to higher wavenumbers as the number of carbon atoms increased, while most bands of the cyclic molecules in this region transitioned to lower wavenumbers. These theoretical results should prove helpful with regard to identifying hydrate deposits from experimental Raman spectroscopic data.

Key words: Density functional theory calculation, Hydrate, Alkane, Stability, Raman spectrum

MSC2000: 

  • O641