Theoretical study on clusters of magnesium

The energetic and structural properties of neutral magnesium clusters Mg-n (n = 2 to 22 and selected clusters up to 309) are investigated by means of density functional theory. The small clusters of sizes n = 4, 10 and 20 show enhanced stability, which is in line with the predictions of the shell model. Larger clusters were selected according to the principle of geometric shell closings; different kinds of shapes and packing types were considered. Among the cluster sizes studied, icosahedral packings are most favourable, which supports the experimental findings. Weak evidence is found for hcp packings to become most stable for large n. The calculated cohesive energies lead to an extrapolated bulk value of 1.4 eV, in reasonable agreement with experiment (1.51 eV). The electronic shell structure of large clusters is discussed in terms of the shell model, which is found to be reliable for up to 40 electrons, while the stability of higher shells is very dependent on the cluster shape.