Ab initio investigation of FeTi-H system

In this study, a first principles search for a possible hydride with high hydrogen storage capacity was carried out in the FeTi intermetallic system. In this regard, formation energies of FeTiHx (x = 1-6) hydrides are systematically investigated on the basis of crystal and electronic structures and structural stability. Total energies were calculated by ab initio pseudopotential method within the generalized gradient approximation (GGA) to density functional theory (DFr). In the stability analysis, mostly the subgroups of the space group of the FeTi structure (P m(3) over bar m), as well as some special cases in which Fe-Ti coordination is similar to P m(3) over bar m were considered. Our calculations predicted the experimental structures of FeTiH and FeTiH2. It was found that, the insertion of hydrogen into the structure causes an increased electron density in the electronic orbitals of Fe which were oriented towards hydrogen atoms. We have also identified a new hydride which is less stable than the experimentally observed ones, having four hydrogen atoms per chemical formula. (C) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.