title: Structural phase transitions induced by pressure in ammonium borohydride.
abstract: A combined experimental and theoretical study of hydrogen-rich ammonium borohydride (NH4BH4) subjected to pressures up to 10 GPa indicates two phase transitions, detected by synchrotron radiation powder X-ray diffraction, Raman spectroscopy and Car-Parrinello molecular dynamics calculations, at 1.5 and 3.4 GPa. The ambient pressure, face-centred cubic phase of NH4BH4 transforms into a highly disordered intermediate structure which then evolves upon increasing pressure into an orthorhombic, distorted CsCl structure. The structure of the latter phase was solved using ab initio computational techniques and from a Rietveld full pattern refinement of the powder X-ray diffraction data.
authors.affiliation: Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6. chris.ratcliffe@nrc-cnrc.gc.ca.
authors.forename: Roxana
authors.initials: R
authors.lastname: Flacau
authors.forename: Yansun
authors.initials: Y
authors.lastname: Yao
authors.forename: Dennis D
authors.initials: DD
authors.lastname: Klug
authors.forename: Serge
authors.initials: S
authors.lastname: Desgreniers
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Ratcliffe