Density functional BMW calculations with the 6-31G* and 6-311+G* basis sets have been employed in order to investigate the structure, vibrational frequencies, relative energies, and vertical ionization potentials of low-lying isomers in the family of doped aluminum clusters XAl12- (X = B, Al, Ga) and XAl12 (X = C, Si, Ge). lsomerization barriers have been also determined. The results are compared with the data of previous similar calculations for endohedral and exohedral isomers of the alane salts Ln+[Al12H12](2-) to analyze similarity and differences between the aluminides and alanes. (C) 2002 Elsevier Science B.V. All rights reserved.