Tang Chunmei, Yuan Yongbo, Deng Kaiming, Liu Yuzhen, Li Xiangyin, Yang Jinlong, Wang Xin
Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, People's Republic of China.
J Chem Phys. 2006 Sep 14;125(10):104307. doi: 10.1063/1.2339022.
The generalized gradient approximation based on density functional theory is used to analyze the geometric and electronic properties of Si @ C(74). It is found that among the five possible optimized geometries of Si @ C(74), the most favorable endohedral site of Si atom is under the center of a pentagon ring on the sigma(h) plane, i.e., Si @ C(74)-5, which is different from the center stable site for Si in C(74) calculated by the semiempirical molecular orbital calculations and molecular mechanics calculations, and it is also different from the stable site, i.e., under a [6, 6] bond along the C(2) axis on the sigma(h) plane in C(74) for metal atoms Ba, Ca, and Eu. The deformation charge density on the sigma(h) plane reveals that the Si-C bonds in Si @ C(74)-5 have covalent character, while the Mulliken charge analysis together with a longer Si-C bond length reveals that the Si-C bonds in Si @ C(74)-5 have ionic character. Therefore, we infer that Si-C bonds in Si @ C(74)-5 contain both covalent and ionic characters.
基于密度泛函理论的广义梯度近似被用于分析硅@碳（74）的几何和电子性质。研究发现，在硅@碳（74）的五种可能的优化几何结构中，硅原子最有利的内包位置在σ（h）平面上五边形环的中心下方，即硅@碳（74）-5，这与通过半经验分子轨道计算和分子力学计算得出的碳（74）中硅的中心稳定位置不同，也与金属原子钡、钙和铕在碳（74）的σ（h）平面上沿C（2）轴的[6, 6]键下方的稳定位置不同。σ（h）平面上的变形电荷密度表明，硅@碳（74）-5中的硅-碳键具有共价性质，而Mulliken电荷分析以及较长的硅-碳键长表明，硅@碳（74）-5中的硅-碳键具有离子性质。因此，我们推断硅@碳（74）-5中的硅-碳键兼具共价和离子性质。
