title: Geometric and electronic properties of endohedral Si @ C74.
abstract: 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.
authors.affiliation: Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, People's Republic of China.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Tang
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Yuan
authors.forename: Kaiming
authors.initials: K
authors.lastname: Deng
authors.forename: Yuzhen
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiangyin
authors.initials: X
authors.lastname: Li
authors.forename: Jinlong
authors.initials: J
authors.lastname: Yang
authors.forename: Xin
authors.initials: X
authors.lastname: Wang