The structures and the binding energies of small Mo clusters from n = 2 to
n = 8 are calculated within a local spin density approximation. Their groun
d-state structure indicates that the bonding properties of Mo atoms tend to
be more directional than those of Cr or Nb atoms. This effect manifests it
self in more buckling and lower symmetry in the ground-state configurations
of Mo clusters. This will eventually result in different ground-state conf
igurations compared to Cr or Nb clusters. The onset of a structural transit
ion from a close-packed structure towards a body-centered cubic structure,
as related to the appearance of a square-shaped face, is already seen in Mo
-6 and in Mo-8.