Bulk and surface properties of hexagonal-close-packed Be and Mg

Density functional theory and a plane-wave basis pseudopotential technique are applied to calculate the bulk and the (0001) surface properties of hexagonal-close-packed (hcp) beryllium and magnesium. The calculations were performed with two forms of the exchange-correlation functional. The bulk properties of the two metals calculated within the generalized gradient approximation (GGA) are closer to the measured ones than the local density approximation (LDA) results are. The GGA also provides results for lattice relaxations, work functions, and surface energies which are in a better agreement with experimental values than the LDA results are. The changes of surface energy and work function with slab thickness varying between 3 and 13 atomic layers were considered. Quantum-size effects did not influence the calculated work function and surface energies significantly.