title: Structure and properties of complex hydride perovskite materials.
abstract: Perovskite materials host an incredible variety of functionalities. Although the lightest element, hydrogen, is rarely encountered in oxide perovskite lattices, it was recently observed as the hydride anion H(-), substituting for the oxide anion in BaTiO3. Here we present a series of 30 new complex hydride perovskite-type materials, based on the non-spherical tetrahydroborate anion BH4(-) and new synthesis protocols involving rare-earth elements. Photophysical, electronic and hydrogen storage properties are discussed, along with counterintuitive trends in structural behaviour. The electronic structure is investigated theoretically with density functional theory solid-state calculations. BH4-specific anion dynamics are introduced to perovskites, mediating mechanisms that freeze lattice instabilities and generate supercells of up to 16 × the unit cell volume in AB(BH4)3. In this view, homopolar hydridic di-hydrogen contacts arise as a potential tool with which to tailor crystal symmetries, thus merging concepts of molecular chemistry with ceramic-like host lattices. Furthermore, anion mixing BH4(-)←X(-) (X(-)=Cl(-), Br(-), I(-)) provides a link to the known ABX3 halides.
authors.affiliation: Laboratory of Crystallography, Department of Condensed Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, CH-1211 Geneva, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Schouwink
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, 8000 Aarhus, Denmark.
authors.forename: Morten B
authors.initials: MB
authors.lastname: Ley
authors.affiliation: Department of Physical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
authors.forename: Antoine
authors.initials: A
authors.lastname: Tissot
authors.affiliation: Department of Physical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
authors.forename: Hans
authors.initials: H
authors.lastname: Hagemann
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, 8000 Aarhus, Denmark.
authors.forename: Torben R
authors.initials: TR
authors.lastname: Jensen
authors.affiliation: Institute of Inorganic Chemistry, Department of Theoretical Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 36 Bratislava, Slovak Republic.
authors.forename: Lubomír
authors.initials: L
authors.lastname: Smrčok
authors.affiliation: Laboratory of Crystallography, Department of Condensed Matter Physics, University of Geneva, Quai Ernest-Ansermet 24, CH-1211 Geneva, Switzerland.
authors.forename: Radovan
authors.initials: R
authors.lastname: Černý