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High‐Temperature Superionic Phase of Mixed Proton Conductor [Rb 0.57 (NH 4 ) 0.43 ] 3 H(SeO 4 ) 2 : Dynamic Twinning and Anomalous Display of Dynamically Disordered Hydrogen Atoms
Author(s) -
Merinov B.,
Bourenkov G.,
Bismayer U.
Publication year - 2000
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(200004)218:2<365::aid-pssb365>3.0.co;2-i
Subject(s) - crystal twinning , crystallography , hydrogen bond , chemistry , trigonal crystal system , hydrogen , phase (matter) , tetrahedron , proton conductor , condensed matter physics , crystal structure , physics , molecule , electrolyte , microstructure , organic chemistry , electrode
The crystal structure of the superionic phase of mixed trirubidium‐ammonium hydrogen biselenate, [Rb 0.57 (NH 4 ) 0.43 ] 3 H(SeO 4 ) 2 , has been determined at T = 370 K. The compound is trigonal, space group R3¯m, a = 6.073(1) Å, c = 22.636(3) Å, V = 722.9(2) Å 3 , M r = 456.34, D x = 3.12 g · cm —3 , μ = 225.5 cm —1 , Z = 3, λ(CuK α ) = 1.541834 Å, F (000) = 631.38, R = 0.025 for 217 unique reflections with I > 3 σ ( I ). A two‐dimensional sublattice of an acid hydrogen bond network linking the SeO 4 tetrahedra was found to be dynamically disordered. Despite the low occupancies of the hydrogen atoms in their crystallographic positions all hydrogen atoms are clearly observed on corresponding electron density maps. This “anomalous” display of the dynamically disordered hydrogen atoms allows the mechanism of the superprotonic transport in M 3 H(AO 4 ) 2 compounds to be elucidated in detail. Dynamic twinning has been observed in our study.