title: Structure of unsolvated magnesium borohydride Mg(BH(4))(2).
abstract: We have determined the structures of two phases of unsolvated Mg(BH(4))(2), a material of interest for hydrogen storage. One or both phases can be obtained depending on the synthesis conditions. The first, a hexagonal phase with space group P6(1), is stable below 453 K. Upon heating above that temperature it transforms to an orthorhombic phase, with space group Fddd, stable to 613 K at which point it decomposes with hydrogen release. Both phases consist of complex networks of corner-sharing tetrahedra consisting of a central Mg atom and four BH(4) units. The high-temperature orthorhombic phase has a strong antisite disorder in the a lattice direction, which can be understood on the basis of atomic structure.
authors.affiliation: Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA. jher@ic.sunysb.edu
authors.forename: Jae Hyuk
authors.initials: JH
authors.lastname: Her
authors.forename: Peter W
authors.initials: PW
authors.lastname: Stephens
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Grigorii L
authors.initials: GL
authors.lastname: Soloveichik
authors.forename: Job
authors.initials: J
authors.lastname: Rijssenbeek
authors.forename: Matthew
authors.initials: M
authors.lastname: Andrus
authors.forename: Ji Cheng
authors.initials: JC
authors.lastname: Zhao