Clusters of the IIA and IIB Elements

CP-like simulations have been applied to the study of the fission and evaporation process of sodium clusters [11, 128]. 

Interest in clusters of the IIA (Mg, Ca, Sr, Ba and Ra) and IIB (Zn, Cd and Hg) elements has been motivated mainly by the fact that these systems may undergo a nonmetal-to-metal transition in their electronic structure as a function of size. The basis for this expectation is simple. On the one hand, bulk samples of these elements are clearly metallic, although, not surprisingly, key properties such as conductivity and plasma frequencies show that their electronic structure (and the Fermi surface in particular) deviates from the ideal free-electron picture much more than in the case of alkali metals [50]. On the other hand, experimental data show that the cohesive energy, equilibrium distances, vibrational frequencies and excitation energies for the homonuclear dimers of these elements are close to those expected for weakly bound van der Waals systems. 

This state of affairs can be rationalized in simple terms. The atoms of these elements have a closed-shell ns np electronic configuration, with a fairly large IP. The energy gap 

Two experimental papers on Hg clusters provide crucial information on the size evolution of the electronic properties in these systems [137, 138]. 

The second, more direct, piece of experimental evidence is provided by the study of the auto-ionization process 

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