摘要
通过对环型硫分子S6～S2 0 同素异构体的实验结构分析 ,用从头算 (abinitio)RHF/ 6 311G (包括BLYP/6 311G 和MP4/ 6 311G )方法进行基态几何结构优化 ,获得了与实验结构相吻合的新的理论稳定构型 .其中S18的两种变体S18(α)和S18(β)的能量相近 ,都是相互稳定的分子构型 .通过计算 ,从理论上推测S2 0 有D4 点群的物相 .还就对称性、偶极矩和红外振动光谱与分子构象的相互关系 ,以及环分子结构与化学活性之间的关系进行了讨论 ,获得了具有实验意义的结论 .
The ground state geometrical optimizations of cyclic sulfur molecules S-6 similar to S-20 have been studied with RHF/6-311 G * and MP4/6-311 G * ab initio methods, and are in agreement with the experimental conformations. The stable molecular structures of recent S(14)both experimental and theoretical are C-5 symmetry and the bond parameters of optimizations are very close to those of experiments. S-18 (alpha) and S-18 (beta) are two types of modification of S-18 ring which have been proved of the same stability due to their close energies. The polymorphic phase S-20 of D-4 point group has also been proved by calculating the structures and comparing the relative energies of D-4 with that of D-2. 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 studying the relations between their electronic structures and chemical reactivities.
