金属硫化物富勒烯Sc_2S@C_(82)的自下而上C_2增长和异构化

The formation of metallic sulfide fullerene Sc_2S@C_(82) via bottom-up C_2 growth and isomerization

两个金属硫化物富勒烯Sc2S@C82-Cs(6)和Sc2S@C82-C3v(8)的结构已经通过单晶X射线衍射验证,但对于其形成机理却知之甚少.本文通过密度泛函理论方法计算研究了Sc2S@C82的不同异构体的热力学和动力学稳定性.结合封闭网络增长模型,研究了Sc2S@C82的形成机理.计算表明,该金属富勒烯是在Sc2S@C80-D5h(31923)的基础上通过C2增长而来,且增长路径是通过中间体Sc2S@C82-Cs(39704)而不是通常认为的Sc2S@C82-Cs(39663);此外,证实了异构体Sc2S@C82-Cs(6)和Sc2S@C82-C3v(8)的相互转化是一个可逆过程;碳催化的Stone-Wales旋转可以大大降低反应的能垒.这些结果对其他金属富勒烯的形成机理具有参考意义.

The structures of endohedral fullerenes Sc2S@C82-Cs（6） and Sc2S@C82-C3v（8） have been definitely confirmed by Single-crystal X-ray Diffraction recently, however their formation mechanisms are yet unknown. Here extensive DFT calculations are performed to identify and compare the favored isomers of Sc2S@C82. The calculated results are in good agreement with the experimental results that Sc2S@C82-Cs（6） and Sc2S@C82-C3v（8） are the two most favored isomers both on thermodynamics and kinetics. The formation of Sc2S@C82 was studied based on the closed network growth model and the interconversion between different isomers of Sc2S@C82. The calculations demonstrate that two pathways may be occurred from Sc2S@C80-D5h（31923）, and the favored pathway is via intermediate Sc2S@C82-Cs（39704） instead of the most well-known Sc2S@C82-Cs（39663）. Furthermore, the interconversion between Sc2S@C82-Cs（6） and Sc2S@C82-C3v（8） is proved to be a reversible process by C-catalyzed bond rearrangement. These calculations can rationalize the experimental observations and put insights into the formation of other metallofullerenes.