title: Improvement in hydrogen desorption from β- and γ-MgH2 upon transition-metal doping.
abstract: A thorough study of the structural, electronic, and hydrogen-desorption properties of β- and γ-MgH2 phases substituted by selected transition metals (TMs) is performed through first-principles calculations based on density functional theory (DFT). The TMs considered herein include Sc, V, Fe, Co, Ni, Cu, Y, Zr, and Nb, which substitute for Mg at a doping concentration of 3.125 % in both the hydrides. This insertion of TMs causes a variation in the cell volumes of β- and γ-MgH2 . The majority of the TM dopants decrease the lattice constants, with Ni resulting in the largest reduction. From the formation-energy calculations, it is predicted that except for Cu and Ni, the mixing of all the selected TM dopants with the MgH2 phases is exothermic. The selected TMs also influence the stability of both β- and γ-MgH2 and cause destabilization by weakening the MgH bonds. Our results show that doping with certain TMs can facilitate desorption of hydrogen from β- and γ-MgH2 at much lower temperatures than from their pure forms. The hydrogen adsorption strengths are also studied by density-of-states analysis.
authors.affiliation: Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, 75120 Uppsala (Sweden). tanveer.hussain@physics.uu.se.|Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden). tanveer.hussain@physics.uu.se.|Centre for Theoretical and Computational Molecular Science, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Qld 4072 (Australia). tanveer.hussain@physics.uu.se.
authors.forename: Tanveer
authors.initials: T
authors.lastname: Hussain
authors.affiliation: School of Engineering, Brown University, Providence, RI 02912 (USA).
authors.forename: Tuhina Adit
authors.initials: TA
authors.lastname: Maark
authors.affiliation: Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, 75120 Uppsala (Sweden).
authors.forename: Sudip
authors.initials: S
authors.lastname: Chakraborty
authors.affiliation: Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, 75120 Uppsala (Sweden).|Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden).
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ahuja
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D028561:Transition Elements; D006859:Hydrogen; D008274:Magnesium
keywords: adsorption; doping; energy storage; hydrogen desorption; thermodynamics