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Title: First-principles predicted low-energy structures of NaSc(BH{sub 4}){sub 4}

According to previous interpretations of experimental data, sodium-scandium double-cation borohydride NaSc(BH{sub 4}){sub 4} crystallizes in the crystallographic space group Cmcm where each sodium (scandium) atom is surrounded by six scandium (sodium) atoms. A careful investigation of this phase based on ab initio calculations indicates that the structure is dynamically unstable and gives rise to an energetically and dynamically more favorable phase with C222{sub 1} symmetry and nearly identical x-ray diffraction pattern. By additionally performing extensive structural searches with the minima-hopping method we discover a class of new low-energy structures exhibiting a novel structural motif in which each sodium (scandium) atom is surrounded by four scandium (sodium) atoms arranged at the corners of either a rectangle with nearly equal sides or a tetrahedron. These new phases are all predicted to be insulators with band gaps of 7.9–8.2 eV. Finally, we estimate the influence of these structures on the hydrogen-storage performance of NaSc(BH{sub 4}){sub 4}.
Authors:
; ;  [1] ; ;  [2]
  1. Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)
  2. Institut Lumière Matière and ETSF, UMR5306 Universite Lyon 1-CNRS, Universitè de Lyon, F-69622 Villeurbanne Cedex (France)
Publication Date:
OSTI Identifier:
22253374
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 12; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CATIONS; CRYSTALLOGRAPHY; HYDROGEN STORAGE; ORTHORHOMBIC LATTICES; SCANDIUM; SODIUM; SPACE GROUPS; X-RAY DIFFRACTION