A theoretical study of Si4H2 cluster with ab initio and density functionaltheory methods

Various isomers of Si4H2 cluster have been investigated with ab initio mole cular orbital and density functional theory (DFT) calculations. Nine local minimum isomers on the potential energy surface have been obtained with bot h Moller-Plesset perturbation theory (MP2) and DFT methods. The Si-4 frame is slightly distorted by the dissociative adsorption of H-2 on it. The most stable isomer of Si4H2 is a classical structure with both hydrogen atoms b onded to a single silicon atom. The nonclassical H-bridged structures are a lso found in the calculations, but predicted to be less stable than the non bridged structures energetically. The formation of the most stable isomer o f Si4H2 from Si-4 and H-2 is proven to be a two-step process and exothermic . The first step is the dissociative adsorption of H-2 on Si-4 cluster by o vercoming an energy barrier of 19.27 kcal/mol, and the second step of conve rsion from the intermediate to the product will readily proceed with a barr ier of only 0.53 kcal/mol. (C) 2001 American Institute of Physics.