Tight binding molecular dynamics study of Ni clusters

A minimal parameter tight binding molecular dynamics scheme is used to study Nin clusters with n≤55. We present theoretical results for relaxed configurations of different symmetries, binding energies, and normal vibrational frequencies for these clusters. Our results are in good agreement with experiment and previous theoretical predictions. We also compare relative stabilities of fcc structures with icosahedral structures. In particular, we find that for clusters whose size allows them to form a close icosahedral geometry (normal or twinned), the closed icosahedral structures yield larger binding energies than fcc structures. The fcc structures, in turn, are found to be more stable than open icosahedral structures for n≤55. Additionally, results for normal vibrational frequencies and ionization energies for n≤10 are also presented. The present results, along with previous successful applications of the method on semiconductor systems, indicate that tight-binding molecular dynamics scheme can be relied on to provide a useful semiempirical scheme in modeling interactions in both covalent and metallic systems.