CNDO Calculations of the g tensors and spin densities of small paramagnetic sulfur-containing anions on magnesium oxide

Abstract

Using a CNDO semiempirical calculation principal values of g tensors and spin densities have been determined for the sulfur-containing molecules SO 2 −. SSO −, S 3 −, SCO −, and CS 2 −,as well as CO 2 −. Bond angles and bond lengths were varied independently. The calculated values were compared with the experimentally determined values for the ions formed on the surface of magnesium oxide. Good agreement was achieved between the calculated and experimental g values: the former was often within experimental error. For SO 2 −, S 3 −, and SCO − the agreement was unique for a particular bond angle and bond length, thus providing a means of estimating the geometric structure for these paramagnetic ions. For S 2O −, CS 2 −,and CO 2 − several structures gave acceptable g values. Where possible, agreement between spin densities in the respective atomic orbitals was used as a secondary criterion to select the best structure. According to the calculations the d-orbital contribution to the total spin density never exceeded 11%.