Theoretical study on the structures and stability of Si2PS isomers

The structures, energetics, spectroscopies, and stabilities of the doublet Si2PS radical are explored at the density functional theory and ab initio levels. Fifteen minima including the chainlike, three-membered ring, four-membered ring, and cagelike structures are located connected by 24 interconversion transition states. The structures of the stable isomers and their relevant transition states are further optimized at the QCISD/6-311G(2d) level. At the CCSD(T)/6-311+G(2df)//DFT/B3LYP/6-311G(d)+ZPVE level, the global minimum is found to be a four-membered-ring cPSiSSi 10 (0.0 kcal/mol) with a 2A′′ electronic state, whereas the cagelike isomer cagePSiSiS 15 (3.5 kcal/mol), the three-membered-ring isomers S-cSiPSi 4 (12.1 kcal/mol), and P-cSiSiS 5 (27.6 kcal/mol) also possess considerable kinetic stabilities (more than 10.0 kcal/mol). The bonding natures and structures of the four isomers 4, 5, 10, and 15 are analyzed. The calculated results are compared with those of the analogous molecules C2PS and SiCPS.