  We studied the structural and the electronic properties of small Mo clusters
(n = 2 ~ 8) via projector augmented wave pseudopotential calculations using
plane wave basis functions. Our results show that the 4s- and 4p-semicore
states play important roles in the description of small Mo clusters. Also, the
dimerization tendency observed in previous theoretical calculations is
significantly reduced when the semicore states are explicitly included as the
valence states.
