Ab initio calculation of geometries and hfs constants of CH 3, SiH 3 and GeH 3 radicals

Abstract

Structures and hyperfine splitting (hfs) constants of the group IV AH 3 radicals, CH 3, SiH 3, and GeH 3, have been calculated by the pseudo-orbital (PO) theory. The optimized out-of-plane angle of SiH 3 is 16.1° and that of GeH 3 is 18.4°. In the group IV AH 3 radicals, SiH 3 was reported to be the most pyramidal from ESR measurement. In this study, however, GeH 3 is calculated to be the most pyramidal in these three radicals. Calculated hfs constants are in fair agreement with experiments except for GeH 3. Vibrational effect for the hfs constants is calculated to be large at the central element. The spin-polarization effect, considered by the PO theory, has been decomposed into shell contributions (inner shells and valence shells). The inner shell spin-polarizations for CH 3 and SiH 3 are not always small and vary largely with the molecular pyramidality. For GeH 3, the spin-polarization occurs mainly in the 4s valence shell and the inner shell contributions are negligibly small.