GEOMETRIC AND ELECTRONIC-STRUCTURES OF FLUORINE BOUND SILICON CLUSTERS

Geometries and energies if SinF- and SinF (n=1-7) were investigated wi th ab initio MO calculations; the Moller-Plesset perturbation and coup led cluster methods were used to take into account the electron correl ation. The F atom is bound to the apex atom in the Si-n frame, and the electronic structures of the Si-n part in SinF- and SinF are similar to those of the corresponding Si-n and Si-n(+), respectively. The calc ulated electron affinities (EAs) of SinF are in agreement with the exp erimental values. The size dependence of EAs of SinF is similar to tha t of the ionization energies of Si-n at n greater than or equal to 5, whereas it is different at n less than or equal to 4. In the HOMO of S inF (n less than or equal to 4), the weak antibonding nature between F and Si greatly makes the Si,F-anions unstable, resulting in small EA. The vibrationally resolved photoelectron spectra (PES) of SinF- (n=1- 3) were measured, and were completely reproduced theoretically. (C) 19 98 American Institute of Physics.