Growth ability and stability indices of clusters

Electronegativity and hardness are well known electronic concepts that help to interpret the electronic rearrangements of atoms in molecules. Parallel atomic concepts can be established that help to understand the growth processes occurring in cluster formation experiments. Those, which are called here the growth ability and the stability index, are essentially the first and second derivatives of the cluster binding energy with respect to the number of atoms, respectively. The first one has not been used before, and by application to transition metal clusters we show that a consideration of both indices helps to interpret the observed cluster mass spectra.