METALLOCARBOHEDRENES - A NEW CLASS OF METAL-CARBON ASSEMBLIES

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