Structural evolution of Aun (n=20-32) clusters: Lowest-lying structures and relativistic effects

The size-dependent evolution of structural and electronic structural motifs between the famous pyramidal Au-20 and I-h-symmetry Au-32 is investigated using density functional theory within the general gradient approximation. When cluster size n increases from 20 to 26, the Calculation results further suggest previous structural evolution. However, when Cluster size n exceeds 26, new very promising ground-state candidates are revealed. The hollow columnar structures with a single additional atom on the axis at n = 27-28 appear instead of the transitional hollow tubelike configurations. The most-stable structures over the range n = 29-32 are obtained by dualization procedure from carbon fullernes. Odd-even alternation behaviors are found in the second difference of binding energies and the gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital over all the size range. The partial density of states and molecular orbitals both display sp-d hybridization due to the relativistic effects in gold clusters that play a dominant role on structural evolution. (C) 2009 Elsevier B.V. All rights reserved.