In this work, the structure, stability, thermodynamic properties and IR spectra of 512 pentagonal dodecahedral isomers (H2O)20 of water clusters with and without central Krypton guest atom was investigated. Especially the effect of central Krypton guest atom on electronic energy and dipole moment in stabilizing the cage of pentagonal dodecahedral water cluster was studied.
Energy optimization of the isolated host cage, krypton guest atom and their complex was carried out using the Becke-three-parameters density functional theory (DFT) with Lee-Yang-Parr functional (B3LYP) and 6-311++G** basis set. Global minimum, dodecahedral isomer dod-3FL2 and its complex with Krypton, Kr[dod-3FL2], having three hydrogen bonds whose donor is daa and acceptor is dda and topological index 2, was found to be the most stable out of all structures investigated with respect to stabilization energy and negative BE(Kr) values.
The clathrate cage remained intact upon inclusion of central Krypton guest atom apart from changes in structural and bond parameters. Average cavity radius was found to be consistent with other studies. The total dipole moment of all optimized 512 pentagonal dodecahedral structures decreases on complexation with krypton guest atom.
The stability with respect to krypton occupancy and predicted OH stretching frequencies of lowest lying dodecahedral isomers and adducts are discussed.