AlP) n , (AlAs) n , (GaP) n , (GaAs) n , (InP) n , and (InAs) n Clusters with n) 1, 2, 3 The structure, geometry, and vibrational frequencies of several isomers of small group III-V (MX) n clusters (n) 1, 2, 3; M) Al, Ga, In; X) P, As) have been investigated using density functional theory. The results reveal the same behavior as in the nitride clusters for monomers and dimers. The Al trimers exhibit a D 3h structure like the nitride, but the gallium and indium trimers exhibit a three-dimensional structure of C s symmetry. The existence of strong X-X bonds dominates both the structure and the vibrations of the Ga and In trimers.