Tang Shu-Wei, Sun Li-Li, Sun Hao, Feng Jing-Dong, Wang Rong-Shun, Chang Ying-Fei, Hao Li-Zhu
Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun, Jilin 130024, People's Republic of China.
J Chem Phys. 2009 Mar 28;130(12):124705. doi: 10.1063/1.3100080.
Stimulated by the mass spectroscopic observation of the metallofullerene Ca@C(44), we have performed a systematic investigation to search for the most stable isomer using HF/3-21G approximately LanL2DZ, HF/6-31+G(d), B3LYP/6-31+G(d), and MP2/6-31+G(d)//B3LYP/6-31+G(d) methods. The Ca@C(44) (D(2):53) isomer with eight adjacent pentagons in the fullerene framework is predicted to possess the lowest energy. The thermodynamics stability explorations of Ca@C(44) isomers at different temperatures show that Ca@C(44) (D(2):53) is the most thermodynamically stable in the temperature range of absolute zero to 4000 K. The encapsulation of Ca atom in C(44) fullerene is exothermic, and the electronic structure of Ca@C(44) (D(2):53) can be described formally as Ca(2+)@C(44) (2-). Further analysis on the frontier molecular orbitals and density of states of Ca@C(44) (D(2):53) suggests that both highest occupied molecular orbital and lowest unoccupied molecular orbital are carbonlike with low Ca character, and the carbon cage possesses high chemical activity. In addition, the vibrational spectrum of Ca@C(44) (D(2):53) has been simulated and analyzed to gain an insight into the metal-cage vibrations.
受金属富勒烯Ca@C(44)的质谱观测结果的启发，我们使用HF/3 - 21G近似LanL2DZ、HF/6 - 31 + G(d)、B3LYP/6 - 31 + G(d)以及MP2/6 - 31 + G(d)//B3LYP/6 - 31 + G(d)方法进行了系统研究，以寻找最稳定的异构体。预测在富勒烯骨架中有八个相邻五边形的Ca@C(44) (D(2):53)异构体具有最低能量。对Ca@C(44)异构体在不同温度下的热力学稳定性探索表明，在绝对零度至4000 K的温度范围内，Ca@C(44) (D(2):53)是热力学上最稳定的。Ca原子封装在C(44)富勒烯中是放热的，并且Ca@C(44) (D(2):53)的电子结构可以形式上描述为Ca(2+)@C(44) (2 -)。对Ca@C(44) (D(2):53)的前沿分子轨道和态密度的进一步分析表明，最高占据分子轨道和最低未占据分子轨道都具有低Ca特征的类碳性质，并且碳笼具有高化学活性。此外，还对Ca@C(44) (D(2):53)的振动光谱进行了模拟和分析，以深入了解金属 - 笼振动。
