Structure and Vibrations of Free Nin Clusters (n ≤ 20).

The binding energy, equilibrium geometry, and vibrational frequencies of small free Ni_n clusters (n ≤ 20) are calculated using interatomic interaction potentials found within the embedded atom method. Calculations of the energy parameter of stability ΔE₂ and dissociation energy show that the most energetically stable clusters are those with the magic numbers of atoms n = 4, 6, 13, and 19. Calculations of atomic vibrations reveal that the dynamic contribution to the stability of clusters is determined by the minimum vibrational frequency, whose extreme values fall on clusters with the magic numbers of atoms n = 4, 6, 13, and 19. The maximum vibrational frequency varies nonmonotonically, and it has unclear extreme values for clusters with n < 19. This result is consistent with the available experimental data on stable structures of small and medium-sized metal clusters. [ABSTRACT FROM AUTHOR]