Ab initio double-ζ (D95) valence bond calculations for the ground states of S2N2 and S42+

The results of double-xi D95 valence-bond (VB) calculations are reported for the ground states of S2N2 and S4(2+). The Mulliken, Lowdin, and Hiberty structural weights are reported for ten Lewis structures that differ in the locations of six pi electrons. The most important Lewis structure for S2N2 is the nitrogen singlet diradical structure (I) with a structural weight of 0.47. For S4(2+) the two singlet diradical structures (XI and XII) with structural weights of 0.23 each are by far the most important individual Lewis structures.