Double vacancies in the cores of silane and tetrafluorosilane.

Abstract

The double core vacancies in silane and tetrafluorosilane are theoretically investigated. The corresponding wave functions and energies are computed using propagator methods, and the results are analyzed in some detail. The analysis is performed by breaking up their binding energies into the most relevant components, such as the hole-hole interaction terms and many-body contributions. An unexpectedly large number of satellite states are predicted, which we take as a possible indication that a breakdown of the molecular-orbital picture of double ionization could also occur in core-vacancy situations. By comparing with self-consistent-field (SCF) results, we encounter an interesting singlet-triplet separation problem that should be typical for multiple vacancies and is shown to be attributed to a deficiency inherent to the SCF procedure itself. The results on the double core holes in Si${\mathit{X}}_{4}$ (X=H,F) are compared and related to single core vacancies and to experimental data on corresponding double-core-excited states.