Structure of RbFeO₂, refined from a reticular pseudomerohedrally twinned crystal with six domains

Abstract

RbFeO(2), rubidium oxoferrate, crystallizes as an orthorhombic structure. The crystals under investigation were composed of six individuals representing reticular pseudomerohedral twins with a pseudocubic twin lattice of index 4 because of the approximate equations a(8)(1/2) = b(2)(1/2) = c. The compound is isostructural with KFeO(2) (KGaO(2) type of structure) and is composed of [FeO(4/2)](-) corner-sharing tetrahedra, forming a three-dimensional cristobalite-like network, with Rb(+) ions occupying its interstices.

The AFeO2 (A=K, Rb and Cs) family: A comparative study of structures and structural phase transitions

“…A detailed analysis of the collected diffraction intensities at room temperature for all the three ferrates under investigation revealed the same twinning phenomenon as already observed for RbFeO 2 [29]. The full pattern can be interpreted as a superposition of six differently oriented but identical diffraction patterns.…”

“…The full pattern can be interpreted as a superposition of six differently oriented but identical diffraction patterns. The handling for data processing of this reticular pseudo-merohedrally twinned crystal is described in detail somewhere else [29,36]. An absorption correction was applied using TWINABS [37] for the room temperature and low temperature measurements; and SADABS [38] for the high temperature measurement, respectively.…”

“…The room and high-temperature structures were refined by fullmatrix least-squares fitting with the SHELXTL software package [39], within the space groups Pbca and Fd3m, whereby the atomic coordinates of RbFeO 2 [29] and CsAlO 2 [40] were used as starting models for the room temperature and high temperature modifications, respectively. Experimental details on crystallographic data and data collection are given in Table 1, atomic coordinates and isotropic Fig.…”

“…In this report we address the iron based subset AFeO 2 with KFeO 2 [28], RbFeO 2 [29], and CsFeO 2 [30]. In retrospective, the first member of the isostructural series, KFeO 2, was erroneously reported to have the filled C9 structure with space group Fd3m (CsAlO 2 structure type) with a=7.99Å [31], but was later known to have a lower symmetry (KGaO 2 type) structure [26].…”

“…In retrospective, the first member of the isostructural series, KFeO 2, was erroneously reported to have the filled C9 structure with space group Fd3m (CsAlO 2 structure type) with a=7.99Å [31], but was later known to have a lower symmetry (KGaO 2 type) structure [26]. Recently the crystal structure of RbFeO 2 was investigated on a six domain twin single crystal and was found to be isostructural to KGaO 2 [29], while CsFeO 2 was reported to crystallize cubic in the CsAlO 2 type of structure [30].…”