The density functional theory study of structures of some compounds having twelve valence electrons with a central sulfur atom

The systematic density functional theory (DFT) computational studies of two bipyramidal twelve valent sulfur compounds were studied targeting a reliable DFT theory model that can handle similar molecular systems. Computational studies are performed with five groups of DFT methods (hybrid, DFT methods with Becke's 88 functional, DFT methods with Xα exchange functional only, DFT methods with Slater's exchange functional, and exchange functionals only) by using the gaussian type basis set. The computation of the structures for the bipyramidal twelve valence electron sulfur molecules is indeed a challenging computational problem. The broadly used HF calculations are not as acceptable as some of the DFT methods that usually perform well when organic molecules are studied. The group of DFT methods with the Xα exchange functional perform very well. It was demonstrated that the basis set containing a d orbital must be used for this study. From these systematic studies, we suggest using the XAPW91/6- 311G(2d,2p) as a method of choice. Even with this method, the computed bond angles might deviate substantially from the experimental data