Ab initio structures and energetics of selected hydrogenated silicon clusters containing six to ten silicon atoms

The structures and energies of eight fully saturated polycyclic polysilanes (Si6H8, Si6H10, Si7H8, Si7H10, Si8H12 Si9H14, Si10H14, and Si10H16) were i nvestigated using ab initio molecular orbital calculations. Structures and vibrational frequencies were computed at the HF/3-21G(d) level. A complete basis set extrapolation method (CBS-4) was used to calculate the energies o f the structures. Heats of formation were evaluated based on homodesmotic r eactions involving disilane, trisilane, and isotetrasilane. The calculation s predict a negative free energy of reaction for cluster formation from sil ane (with H-2 as a by-product) for conditions typically used in chemical va por deposition of silicon from silane. (C) 1999 Elsevier Science B.V. All r ights reserved.