Wafers, platelets, rods and spheres: Using DFTB to determine the structural
minima of atomic clusters

Koblar A. Jackson, jackson@phy.cmich.edu, Physics Department, Central Michigan
University, Mt. Pleasant, MI 48859

We have developed a completely unbiased search method for finding the most
stable structure of intermediate-sized atomic clusters. The method takes
advantage of the relative speed of the density functional-based tight binding
(DFTB) method to identify a large number of low-lying local minima on the DFTB
energy surface. It then exploits the density functional theory (DFT) foundation
of the DFTB to make the jump to the DFT energy surface, so as to result in the
fully optimized ground state structure at the DFT level of theory. The power of
the method will be illustrated through applications to Sin and Cun, systems
which show a fascinating array of cluster shapes. In both cases, the predicted
ground state structures are validated by comparing calculated results to
structurally sensitive experimental data such as ionization potentials, ion
mobilities, vertical detachment energies and photoelectron spectra.