We have studied the energetical and structural properties of copper cluster
s (Cu-n, n = 2-6, 8, 9, 13, 14, 25, and 29) and films (with n(L) = 1, 2, an
d 3 layers) adsorbed on MgO(100) by means of first principles density funct
ional calculations. We find that Cu-Cu interactions dominate over Cu-surfac
e interactions, so that three dimensional (3D) structures are largely prefe
rred with respect to two dimensional (2D) ones. This indicates a Volmer-Web
er growth mode for Cu on MgO(100), in agreement with recent experimental ob
servations.