First-principles study of structural stabilities and electronic characteristics of Mg-La intermetallic compounds

A first-principles pseudopotential plane-wave method based on density functional theory is used to investigate the crystal and electronic structure of Mg-La intermetallic compounds with different types of structure. The obtained lattice constants a(0) for all intermetallics considered are very close to the corresponding experimental values. The calculation of cohesive energies indicated that the structure stability of Mg-La alloy will become higher with increasing La element independent on crystal structure type. The calculations of formation heats showed that the alloying abilities of Mg3La, Mg2La and MgLa were much stronger than Mg12La and Mg17La2, while the Mg17La2 alloying ability was slightly higher than Mg12La alloy. The energy band and the densities of states (DOS) of these intermetallic compounds revealed that the bonding occurred mainly among the valence electrons of Mg 3s, 2p and La 5d, 4f orbits, and the discrepancy in the stability of Mg-La intermetallic compounds could be attributed to the variation of bonding electron numbers at low-energy region of Fermi level. (C) 2007 Elsevier B.V. All rights reserved.