Ni_n(n=2～20)团簇的结构

Equilibrium geometries of Ni_n(n=2～20) clusters

使用经验势和遗传算法 (GeneticAlgorithm) ,得到了Nin(n =2～ 2 0 )团簇的平衡结构和束缚能。对于小的团簇 (Ni2 ～Ni6) ,所得到的结果与基于第一性原理密度泛函的计算相一致。结果表明 ,团簇的结构不同于块体且随尺度发生引人注日的变化。每原子平均束缚能Eb 随尺度单调增长。根据过渡金属团簇表面原子配位数与电离势 (IP)的一个解析表达式计算所得的电离势与实验结果基本一致。由基态能量对分裂途径(FragmentationChannels)的分析表明 ,失去二聚体 (Dimer)在能量上是优先的。同时将计算所得的结构与Nin团簇吸收N2

The equilibrium geometries and the bihding energies of Ni n(n=2～20) clusters have been calculated by using an empirical many body potential and a Genetic Algorithm(GA). For small clusters ( n =16), the potential is found to reproduce the geometries based on first principles density functional calculation. It is shown that the clusters do not mimic the bulk structure and undergo significant geometrical changes with size. The binding energy per atom increases monotonically with size. Using an analytic formula for ionization potentials via effective coordination number, ionization potentials are calculated and the results are in reasonable agreement with experiment. An analysis of the fragmentation channels based on the ground state energies shows the loss of the Ni 2 dimer to be the most energetically favorable channel. The calculated geometries are compared with those derived from recent experiments on N 2 adsorption on Ni n clusters.