Ab-initio mol. dynamics studies are presented of selected microclusters of sodium, silicon and magnesium. From the anal. of the at. trajectories the authors can identify in some cases the existence of different isomers and the isomerization pathways. Vibrational spectra at low temps. are calcd.; they can be used as a very sensitive structural probe also for Na clusters, where the electronic properties are quite insensitive to the geometry. [on SciFinder (R)]