密度泛函方法研究Ru_n(n=9～26)金属团簇

Density Functional Study on Ru_n(n=9～26) Metal Clusters

采用密度泛函理论中的广义梯度近似（DFT／GGA）方法，对Ru。团簇（n=9-26）的几何结构与稳定性、团簇表面的Ru与内部Ru间相互作用进行了研究。结果表明：将金属团簇体系放大后，基态稳定结构的原子平均束缚能Eh随着团簇尺寸的增大而增大，当原子数n=26时，Eb=-6．69eV，与大块金属的Eh（-6．74eV）接近，表明其已接近大块金属的性质；Ru26的平均间距R=2．65A，与理论值2．70A和实验值2．704A相近；平均配位数CN随着n值的增大而增大，呈现收敛于块体值的趋势。另外，由于大块金属表面的原子不能与足够的原子配位形成饱和的配位结构，所以其上的电子向内层原子转移，使得内层Ru原子呈负电荷，而外层原子呈正电荷，最终导致内层原子之间的相互作用增强而导致键的收缩。外层原子之间键的减弱，从而出现所谓的“驰豫效应”。

In this paper, the geometry, stability, interaction between surface and inner Ru atom of Run clusters are investigated by Density Functional Theory （DFF）. The average atom binding energy increases with the increase of the atom number for magnified metal clusters. When n = 26, the binding energy which is comparable to that of bulk metals（-6.74eV） is -6.69eV, which indicates that the binding energy approaches to the property of bulk metals; The average bond distance is 2.65A, which is close to theoretic（2.70A） and experimental values（2.70A）; The average coordination number（CN） presents the trend of convergence to bulk metals. The lack of coordinative saturation for the exterior atoms of the cluster implies that some electrons, which in the bulk metal would be involved in bonding interactions with atoms that are absent in the cluster, are free to migrate to the central atom, which make the central Ru atoms have negative effective charges and surface Ru atoms have positive charge in all clusters, results in the appearance of relaxation effect.