Ab initio MO calculationsof structures and electronic states of SF6 andSF6-

Abstract

Geometrical and electronic structures of SF6 and SF6- have been determined using ab initiomolecular orbital calculations in order to shed light on themechanism of electron capture of SF6. The calculations(MP2/6-311G(d) + sp and MP2/6-311 + G(d)levels) showed that both SF6 and SF6- haveOh symmetry, while the S-F bond of SF6- isabout 10% longer than that of SF6, indicating that thestructure of SF6 is deformed along the S-F symmetricstretching mode by accepting an excess electron. The calculations showed that the adiabatic electron affinities ofSF6 are positive (0.49-1.39 eV), which is in reasonableagreement with the experimental values (0.32-1.49 eV).The potential energy curve calculated as a function of an S-F bondof SF6- showed that SF6- is bound withrespect to its dissociation limit (SF5- + F). The mechanism of electron capture of SF6 is discussed on thebasis of the theoretical results.