金属硫化物富勒烯Sc_2S@C_(90)的结构与性质

Structures and Properties of Metal Sulfide Fullerene Sc_2S@C_(90)

Sc2S@C90存在的信号已经被质谱检测到,但其结构还没有得到表征.为了研究Sc2S@C90的结构和性质,通过密度泛函理论计算方法对Sc2S@C90的异构体进行了系统的筛选.计算结果表明,能量最低的两个异构体分别为Sc2S@C90:99913和Sc2S@C90:99915.对Sc2S@C90在0到4000 K温度下的相对浓度进行了评估,结果显示,Sc2S@C90:99913和Sc2S@C90:99915可以在高温下共存.分析研究了Sc2S@C90的内嵌团簇与碳笼间的键连关系和相互作用特性.这些研究可为Sc2S@C90的结构确定提供指导.

Metallic sulfide fullerene Sc2S@C90 has been detected by mass spectra but not been isolated and structurally characterized. It is impossible to perform extensive tests on Sc2S@C90 due to its low yield, quantum chemical calculations thus become an important method to predict or identify its structure and properties. Here a systematic density functional theory study are first performed on 15756 isomers of fullerene C90 and their anions with 0-3 pairs of fused-pentagons, then 30 isomers of metallic sulfide fullerenes Sc2S@C90 are constructed by putting ScaS into the selected candidate cages with dif- ferent orientations and geometrical optimizations are perfi3rmed on these isomers with the density functional theory method. The calculated results demonstrate that the two lowest-energy isomers are Sc2S@C90：99913 and Sc2S@C90：99915, respectively. Both isomers satisfy the isolated-pentagon rule. To clarify the relative stabilities of the five lowest-energy isomers of Sc2S@C90 at high temperatures, enthalpy-entropy interplay has been taken into consideration with respect to the temperature range of up to 4000 K; the calculations demonstrate that the two lowest-energy isomers of 5c2S@C90 may coexist in the soot at high temperatures. Structural analysis demonstrated that the two isomers can transfer into each other by two Stone-Wales rotations, further suggesting the possibility of interconversion between them. Molecular orbital analysis indicates that Sc2S cluster transfers four electrons to the cage; however nature charge analysis demonstrates the charges transferred from the encaged cluster to the parent cage is much smaller than that with the simple molecular orbital analysis. The quantum theory of atoms in molecules is used to investigate the connectivity and interaction nature between the encaged cluster and parent cage. The results show that there are strong interactions between the encaged cluster and parent cage. The simulated infrared spectra of the two lowest-energy isomers are provided to assist future experimental identification and characterization of the structure of Sc2S@C90.