A parallel study of Ni@Si12 and Cu@Si12 nanoclusters

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The Ni@Si12 and Cu@Si12 clusters are studied in parallel within the framework of the density functional theory using the hybrid functional of Becke-Lee, Parr and Yang (B3LYP), emphasizing the differences and similarities in structural and electronic properties. The dominant structures for both clusters are a distorted hexagonal structure of Cs symmetry and a distorted octahedral structure of D2d. For Ni@Si12 the two structures are practically isonergetic whereas for Cu@Si12 the energy difference of the D2d structure from the lowest Cs structure of hexagonal origin is about 0.7 eV, at the B3LYP/TZVP level of theory. Contrary to Cu@Si12 for which the well known Frank–Kasper (FK) structure of C5v symmetry is a real local minimum of the energy hyper-surface (although higher by more than 1.6 eV from the global minimum), for Ni@Si12 the FK structure is dynamically unstable. The HOMO-LUMO gaps, the binding energies per atom and the embedding energies for Cu@Si12 clusters are smaller by 0.5, 0.1 and 1.1 eV, respectively compared to the Ni@Si12 clusters. This is attributed to different type of bonding in the two clusters.