STRUCTURAL PATTERN AND THE STABILITY OF WATER CLUSTEkS IN GAS HYDRATES

Abstract

The scarcity and the high demand for natural gas lead to the search for alternative energy sources. Gas Hydrate is one of such energy sources which is not yet explored. The main reason for this is their existence at extreme conditions like very low temperatures and high pressures at which experimental studies are difficult. Modeling can give insight to the structure and stability of Gas Hydrates at favorable conditions for their effective use. Structural pattern and the stability of various types of water cages that occur in gas hydrates viz. Dodecahedral (512), Tetrakaidecahedral (51262) and Hexakaidecahedral (51264) cages are studied using the SWB and SWEB models and density functional Becke97-D in conjunction with cc-pVTZ basis set. In addition to the dodecahedral cages, the validity of these models is also tested for comparing the relative stability of isomers of other families of (1420)20 clusters viz. Edge-sharing pentagonal prisms (ESPP), Face-sharing pentagonal prisms (FSPP), Fused cubes (FC), and Irregular-dodecahedron (IDD). The fused cages formed by the combinations of two dodecahedral cages, two irregular-dodecahedral cages and a dodecahedral cage with an irregular-dodecahedral cage are also studied. A strategy is explained for obtaining the fused cages having maximum number of strong hydrogen bonds. The influence of various structural features such as homodromic rings, heterodromic rings and AADD type of water molecules on the stability of all the above geometries has also been explained.