Energetically competitive growth patterns of silicon clusters: Quasi-one-dimensional clusters versus diamond-like clusters

Silicon clusters with a diamond-like core and energetically competitive non-diamond clusters were studied using the nonconventional tight-binding molecular dynamics simulation method. Non-diamond clusters were constructed according to a quasi-one-dimensional pentagon-based regular growth pattern. A nontrivial competition between surface and core reconstructions in the clusters, in order to reach energetically favorable atomic arrangements, was observed. This prevents unlimited growth via the one-dimensional pattern. Starting from Si43, there was substantial deviation from the stacked pentagon motif, and for Si61, one end of these clusters became almost two-dimensional. Clusters with a diamond-like core were subjected to substantial reconstruction. These were energetically unfavorable relative to non-diamond clusters for the sizes considered (≤71 atoms). The importance of capped pentagon motifs in the surface reconstruction for energetically competitive nanometer-size diamond-like clusters was demonstrated. A lower bound of 115 atoms for the transition from non-diamond structure to diamond-like structure is estimated by extrapolation of the present results.