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 sho w enhanced stability, which is in line with the predictions of the shell mo del. 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 energie s lead to an extrapolated bulk value of 1.4 eV, in reasonable agreement wit h 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 u p to 40 electrons, while the stability of higher shells is very dependent o n the cluster shape.