First-principles electronic structure calculations have been carried out on NbN clusters with N = 2 - 23 atoms using ultrasoft pseudopotentials, a plane wave basis and generalized gradient approximation for the exchange-correlation energy, to elucidate the growth behavior and the evolution of the electronic structure. Our results show that clusters with N>13, prefer high coordination structures with hexagonal antiprisms except for N = 15 which has a distorted body centered cubic structure (bcc). Clusters with N>2 favor lowest spin configurations. Of particular importance is the finding that icosahedral growth is not favored in these clusters. There are large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gaps for clusters with 4, 6, 8, 10, and 16 atoms. These are in agreement with the observed low reactivities as well as the photoemission data of 6-, 8-, 10-, and 16-atom clusters. Clusters with 4, 8, 10, 15, and 16 atoms are found to be magic, suggesting the importance of the atomically closed shell bcc structure of Nb15 even though the HOMO-LUMO gap is small. However, Nb6 is not magic. A dimerization behavior is obtained in Nb10 and it is found to be even more prominent in the isoelectronic V10. But, this tendency is absent in Ta10. The calculated binding energies, electronic structures and fragmentation behavior are in good agreement with available experimental data.
|Number of pages||11286281|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2002 Mar 15|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics