Density Functional Theory Studies of the Binary Systems [BxAl13-x] (x=0 similar to 13)

作者：Huang Min; Xu Chang; Cheng Longjiu^*

来源：Acta Chimica Sinica, 2016, 74(9): 758-763.

DOI：10.6023/A16050230

• density functional theory
• [BxAl13-x](-) (x=0 similar to 13) clusters
• optimization
• molecular orbitals
• adaptive natural density partitioning

In this paper, the global minimum search and structural optimization for the B-Al binary clusters [BxAl13-x](-) (x=0 similar to 13) are performed using the genetic algorithm (GA) method coupled with density functional theory (DFT). The effects of composition on the atomic structures, electronic properties including the energy gaps and vertical detachment energies of B-Al binary clusters are discussed. The results distinctly reveal a three dimensional (3D) to (quasi -)planar (2D) structural transition as a function of x upon increasing the number of boron atoms. When x is in the range of 0 to 7, the clusters are Al-rich and the B-Al binary systems maintain the 3D structure. Whereas, the binary system trends to be quasi-planar structure, and the critical B:Al ratios for the 2D-3D transition are between x=7 and 8. To study the stability of the [BxAl13-x] clusters, we defined the relative energy (E-rel=E([BxAl13-x])-xE(B-13(-))/13-yE(Al-13(-))/13), where the cluster with a more negative Ere, is more stable. At x=1, Ere, is the most negative, indicating the highest stability. In order to further understand the stability of clusters, the vertical detachment energies (VDE) and the HOMO-LUMO energy gaps (EH-L) of [BxAl13-x](-) (x=0 similar to 13) clusters are also calculated. The results show that the energy decreases with the increasing number of B atoms, indicating a lower stability. The largest EH-L of BAl12- cluster indicates that it is the most stable among all the series of this clusters. Molecular orbitals (MO) of BAl12- cluster are analyzed and the result shows that the electronic shells of 1s(2) and 1p(6) are virtually unchanged when the central Al atom is replaced by the B atom. It also indicates that the electron shell closing model could be regarded as a simple but valid tool for explaining the structures and stabilities of metal clusters. Chemical bonding analysis by Adaptive Natural Density Partitioning (AdNDP) method for the B-13(-) cluster reveals that it is a pi-antiaromatic system with 8 delocalized pi-electrons.

• 出版日期2016-9-15
• 单位安徽大学