Within the framework of density functional theory, we investigate the structural properties, electronic structure, and the chemical stability of magnesium alanate (Mg(AlH4)(2)), a complex hydride for hydrogen storage, using the projector augmented plane wave method. The calculated structural properties of magnesium alanate compare well with the recent experiment. A detailed study of the electronic structure and charge density redistribution reveals the orbital hybridization and characteristics of bonding orbitals within the complex hydride. We found an ionic covalent bonding between Al and H in the (AlH4)(-) anionic complexes embedded in the matrix of Mg2+ cations. The calculated reaction energy of Mg(AlH4)(2) is in good agreement with the experimentally determined value. (c) 2006 Elsevier B.V. All rights reserved.