Direct evaluation of the density of states of simple metal clusters via forced oscillator method (FOM): a preliminary report

Direct evaluation via forced oscillation method of the electronic state density of sizable clusters

“…Unfortunately, as already noticed in previous work, 19,35 this strategy is not fully portable to all geometries. In particular, for BCC clusters (where N = 2L 3 − 3L 2 + 3L − 1), considering the computational facilities at our disposal, we were uncapable to investigate structures containing more than 1729 sites, because of the fact that for this symmetry the number of vectors required is not fixed and depends on the cluster size (2L vectors are now necessary) and no general rule for multiplicity and periodicity is available.…”

“…Actually, we had previously put in evidence 19 that remarkable advantages were achieved in the case of SC and FCC clusters because of synergetic effects of FOM-MSS (matrix storage strategy) with much more modest results documentable in the BCC case. Considering the profile of this journal and its audience, we think it of some utility to digress a little bit about this occurrence, trying to go more deeply into the reasons of the (partial) failure found in the case of BCC clusters.…”

“…In this article, we propose to provide additional evidence of the FOM virtues, exploring the potentialities of the method in the study of the electronic structure of sizable metal-clusters. In a preliminary work, 19 we brought some examples of the efficiency of the approach on the basis of DOS results obtained for some cubic SC, FCC, and BCC cluster geometries, described according to a tight-binding model (TBM) able to take into account size-and surface-effects. Indeed, our experience with FOM, matured from DOS studies of sizable cubic-symmetry clusters, had been very positive, especially in the case of simple cubic (SC) and face-centered cubic (FCC) aggregates, thanks to our capacity of storing efficiently the sparse Hamiltonian matrices involved (vide infra), whereas for body-centered cubic (BCC) structures the results were not so comforting as to the size of the tractable clusters.…”