Structure And Stability Of Sc₂B_n And Ti₂B_n Clusters

With the development of clusters research, the doped clusters began to cause wide attentions. The structures and properties of clusters have changed greatly due to the inserting of heteroatom. Thus, it is expected to uncover the formation mechanism and the stability rule of the doped clusters theoretically. These results of research will provide some theoretical basis and guidance for the popularization and application of these clusters.In this paper, the structures and stabilities of Sc2Bn (n=1-10) and Ti2Bn (n=1-10) have been systematically investigated by using the density theory (DFT) at the B3LYP/6-311+G(d) level. All the results are summarized as follows.The growth behaviors, stabilities, and electronic properties of the Bn and Sc2Bn, n up to10, clusters are investigated theoretically at the B3LYP level by employing6-311+G(d) basis sets. Calculation results showed that (1) The equilibrium structures of pure Bn clusters are fundamentally changed due to the encapsulation of the Sc atom, excluding Sc2B and Sc2B3cluster, others are pyramid structures, and for Sc2B2Sc2B4and Sc2B5, B atoms form a semicircle around the Sc-Sc bond, for Sc2Bn(n=6-9), Sc atoms on atop-site of bipyramid structures.In various low-lying metastable isomers of Sc2Bn(n=1-10),we can find the planar structure with two Sc atoms locate at the head and the tail.The spin multiplicity of the ground state of Sc2Bn is2、1、2、1、2、1、2、1、2、1, respectively.(2)The average atomic binding energies, fragmentation energies, second-order energy differences and HOMO-LUMO gaps are calculated and discussed. The dopant of the Sc atom improves the stability and metallicity. Sc2Bn clusters at n=4,7possess relatively higher stability, and the magic numbers of the Sc2Bn clusters are4,7.(3) NBO analyses show that Charge always transfers from the Sc to the B atom with the increase of size and indicates that Sc acts as an electron donor in all Sc2Bn clusters. There are strong overlap between d electron of Sc atom and p electron of Bn clusters and the Sc atom is at the positive condition.The growth behaviors, stabilities, and electronic properties of the Ti2Bn, n up to10, clusters are also investigated theoretically at the B3LYP level by employing6-311+G(d)basis sets. Calculation results showed that (1) The equilibrium structures of pure Bn clusters are fundamentally changed due to the encapsulation of the Ti atom, excluding Ti2B cluster, others are pyramid structures, and for Ti2Bn(n=2-5), B atoms form a semicircle around the Ti-Ti bond, for Ti2Bn (n=6-9),Ti atoms on atop-site of bipyramid structures.ln various low-lying metastable isomers of Ti2Bn(n=1-10),we can find the planar structure with two Ti atoms locate at the head and the tail.The spin multiplicity of the ground state of Ti2Bn is2、5、4、3、2、3、4、1、2、3, respectively.(2) The dopant of the Ti atom improves the stability and metallicity, but reduces the energy gap in most cases except n=7. Ti2Bn clusters at n=7,9possess relatively higher stability, and the magic numbers of the Ti2Bn clusters are7,9.(3) NBO analyses show that Charge always transfers from the Ti to the B atom with the increase of size and indicates that Ti acts as an electron donor in all Ti2Bn clusters. There are strong overlap between d electron of Ti atom and p electron of Bn clusters and the Ti atom is at the positive condition.