title: Structures and stability of lithium monosilicide clusters SiLi(n) (n = 4-16): what is the maximum number, magic number, and core number for lithium coordination to silicon?
abstract: In the coordination, hypervalent and cluster chemistry, three important characteristic properties are the maximum coordination number, magic number, and core coordination number. Yet, few studies have considered these three numbers at the same time for an ML(n) cluster with n larger than 8. In this article, we systematically studied the three properties of SiLi(n) (n = 4-16) clusters at the B3LYP/6-31G(d), B3LYP/6-311++G(2d), and CCSD(T)/6-311++G(3df)//B3LYP/6-311++G(2d) (for energy only) levels. Various isomeric forms with different symmetries were calculated. For each SiLi(n) (n = 4-9), silicon cohesive energy (cE) from SiLi(n) --> Si + Li(n) reaction, vertical ionization potential (vIP), and vertical electron affinity (vEA) were obtained for the lowest-energy isomer. We found that the maximum Li-coordination number of Si is 9, which is the largest number among the known MLi(n) clusters. All cE, vIP, and vEA values predicted that 6 is the magic Li-coordination number of Si. For small SiLi(n) (n < or = 6) clusters, Li atoms favor direct coordination to Si, whereas for larger SiLi(n) (n > or = 7) clusters, there is a core cluster that is surrounded by excessive Li atoms. The core Li-coordination number is 6 for SiLi(n) (n = 7,8), 7 for SiLi(n) (n = 9,10), 8 for SiLi(n) (n = 11-15) and 9 for SiLi(n) (n > or = 16). Through the calculations, we verified the relationship between the structure and stability of SiLi(n) with the maximum coordination number, magic number, and core coordination number.
authors: State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
authors: Ning
authors: N
authors: He
authors: Hong-Bin
authors: HB
authors: Xie
authors: Yi-Hong
authors: YH
authors: Ding