title: Vibrational properties of polyanionic hydrides SrAl2H2 and SrAlSiH: new insights into Al-H bonding interactions.
abstract: The vibrational properties of the recently discovered aluminum hydrides SrAl2H2 and SrAlSiH have been investigated by means of inelastic neutron scattering (INS) and first-principles calculations. Both compounds contain Al-H units being part of a two-dimensional polyanionic layer, [(AlH)(AlH)]2- and [Si(AlH)]2-, respectively. The INS spectrum of SrAlSiH is characterized by very weakly dispersed Al-H modes with well-resolved overtones, while SrAl2H2 yields a solid-state dispersed phonon spectrum. The frequency of the stretching mode of the Al-H unit in SrAlSiH is the hitherto lowest observed for a terminal Al-H bond. At the same time, SrAlSiH displays the highest decomposition temperature known for an aluminum hydride compound. It is proposed that the stability of solid-state aluminum hydrides correlates inversely with the strength of Al-H bonding.
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287-1504, USA.
authors.forename: Myeong H
authors.initials: MH
authors.lastname: Lee
authors.forename: Otto F
authors.initials: OF
authors.lastname: Sankey
authors.forename: Thomas
authors.initials: T
authors.lastname: Björling
authors.forename: David
authors.initials: D
authors.lastname: Moser
authors.forename: Dag
authors.initials: D
authors.lastname: Noréus
authors.forename: Stewart F
authors.initials: SF
authors.lastname: Parker
authors.forename: Ulrich
authors.initials: U
authors.lastname: Häussermann