中性及其带电Cu_n(n=2～12)团簇体系的第一性原理计算研究

Density-functional investigations on the neutral and chargedCu_n(n=2～12) clusters

结合半经验原子间势及遗传算法，采用密度泛函理论，系统计算研究了Cun（n=2～12）及Cu±n（n=2～12）的基态与低激发态的几何结构与电子结构．结果表明：对中性团簇在n=3～6时基态为平面结构，而对于带电体系n=3～5时基态为低维结构，其中平面结构都以三角形为基本单元；对含更多原子的立体结构，基态主要以五角双锥为基本结构单元，传统的高对称性结构在小铜团簇基态中不占优势；计算所得Cun（n=2～12）中性体系结合能与实验结果完全一致，而结合带电体系计算所得团簇电离能与亲和势也与实验相符合；团簇电子结构的相关曲线（电离能、亲和势、二阶差分能）均呈现明显的奇偶振荡现象，这与含偶数电子Cu团簇的相对高稳定性密切相关．

Combined with the semi-empirical inter-atomic potential, the geometrical and electronic properties of the ground- and low-lying states of Cun（n=2-12） and Cun （n=2-12） clusters are investigated systematically by density-functional calculations. Our results show that： the ground-state geometries prefer to linear or planar structures for the Cu, （n=2- 6） and Cu±n （n=2-5） clusters and the planar structures are all base on triangles, while for the larger clusters, the pentagonal bi-pyramids are the basic units to form the ground-state geometries, and the traditional high-symmetric structures do not domi- nate to the ground-states for these small copper clusters. The calculated binding energies of Cun （n=2- 12） clusters are in very good agreement with the experimental results, and the obtained ionization potentials （IPs） and electron affinities （EAs） are also in agreement with the observations; Several electronic properties （such as the IPs, EAs and the second-order energy differences） all exhibit oscillations, which can be due to the relatively high stabilities of the copper clusters containing even number electrons.