METALLOCARBOHEDRENES - A NEW CLASS OF METAL-CARBON ASSEMBLIES

The electronic structure and stability of metallocarbohedrenes (met-ca r) and cubic structures containing Ti and C or N have been studied usi ng the ab-initio density functional approach. We show that while the m et-car and the cubic structures have comparable binding energies per a tom for the case of carbides, the cubic structures are more stable for metal-nitrogen systems. This change in behavior is shown to be relate d to the differences in the nature of electronic bonds which stabilize the two structures. By studying small TinCm and TinNm (n + m < 6) clu sters, we identify these electronic features and show that the met-car and cubic arrangements represent two different families whose formati on is governed by the composition of the beam.