The ab initio Studies on the Structures of Cyclic Sulfur and Their Applications

The ground state geometrical optimizations of cyclic sulfur molecules S6~S20 have been studied with RHF/6-311G* and MP4/6-311G* ab initio methods, and are in agreement with the experimental conformations. The stable molecular structures of recent S14both experimental and theoretical are Cs symmetry and the bond parameters of optimizations are very close to those of experiments. S18(α) and S18(β) are two types of modification of S18ringwhich have been proved of the same stability due to their close energies. The polymorphic phase S20 of D4 point group has also been proved by calculating the structures and comparing the relative energies of D4with that of D2. Otherwise, The relationships of molecular conformation models with symmetries, dipole moments and vibrational frequencies have been discussed. The significant applications of cyclic sulfur have been deduced by studyingthe relations between their electronic structures and chemical reactivities.