61.
We report results of the atomic and electronic structures of Al
7C cluster using
ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al
7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett.
316, 31 (2000)] of magic behavior of Al
7C
- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al
7C
- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al
7N which has the same number of valence electrons as in Al
7C
- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al
7N)
2 to study interaction between magic clusters.
Received 28 July 2001
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