Metastable MgH<inf>2</inf> phase predicted by first principles calculations

Abstract

MgH2is a promising compound for hydrogen storage. Its relatively high stability has been the main obstacle for practical applications. Here, the authors report a first principles prediction of a metastable phase of MgH2. The predicted phase is characterized by tetragonal symmetry (I41/amd, group 141) with the lattice parameters a=0.3813 nm and c=0.9416 nm and meets all the mechanical stability criteria. Its heat of formation is -58.03 kJ/mol H2, which is much less negative than that of the α:-MgH2phase (-76 kJ/mol H2). Hence, the tetragonal structure is more desirable than the α-MgH2for practical hydrogen storage applications. © 2006 American Institute of Physics.