Molecular simulations and density functional theory calculations of bromine in clathrate hydrate phases

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DOIResolve DOI: http://doi.org/10.1063/1.4940321
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TypeArticle
Journal titleJournal of Chemical Physics
ISSN0021-9606
Volume144
Issue4
Article number44501
SubjectChemical bonds; Chlorine; Density functional theory; Distribution functions; Hydrates; Hydration; Iodine; Molecular dynamics; Molecules; Quantum chemistry; Van der Waals forces; X ray diffraction; Autocorrelation functions; Electrostatic potentials; Molecular dynamics simulations; Non-bonding interactions; Non-covalent interaction; Quantum chemical calculations; Radial distribution functions; X-ray diffraction studies; Bromine
AbstractBromine forms a tetragonal clathrate hydrate structure (TS-I) very rarely observed in clathrate hydrates of other guest substances. The detailed structure, energetics, and dynamics of Br2 and Cl2 in TS-I and cubic structure I (CS-I) clathrate hydrates are studied in this work using molecular dynamics and quantum chemical calculations. X-ray diffraction studies show that the halogen-water-oxygen distances in the cages of these structures are shorter than the sum of the van der Waals radii of halogen and oxygen atoms. This suggests that the stabilizing effects of halogen bonding or other non-covalent interactions (NCIs) may contribute to the formation of the unique tetragonal bromine hydrate structure. We performed molecular dynamics simulations of Br2 and Cl2 clathrate hydrates using our previously developed five-site charge models for the dihalogen molecules [Dureckova et al. Can. J. Chem. 93, 864 (2015)] which reproduce the computed electrostatic potentials of the dihalogens and account for the electropositive σ-hole of the halogen bond donor (the dihalogen). Analysis of the radial distribution functions, enthalpies of encapsulation, velocity and orientation autocorrelation functions, and polar angle distributions are carried out for Br2 and Cl2 guests in various cages to contrast the properties of these guests in the TS-I and CS-I phases. Quantum chemical partial geometry optimizations of Br2 and Cl2 guests in the hydrate cages using the M06-2X functional give short halogen-water distances compatible with values observed in X-ray diffraction experiments. NCI plots of guest-cage structures are generated to qualitatively show the relative strength of the non-bonding interactions between dihalogens and water molecules. The differences between behaviors of Br2 and Cl2 guests in the hydrate cages may explain why bromine forms the unique TS-I phase.
Publication date
PublisherAIP Publishing
LanguageEnglish
AffiliationNational Research Council Canada; Security and Disruptive Technologies
Peer reviewedYes
NPARC number21277499
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Record identifierf4028a6a-2b40-4d77-b774-1d0e8e181acb
Record created2016-03-09
Record modified2017-03-23
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