STRUCTURE AND TWINNING OF RBLICRO4 CRYSTALS

The crystal structures of the G3 (space group P31c) and G2 (space group P6(3)) phases of RbLiCrO4 have been determined from X-ray diffraction data (Mo Kalpha radiation) at 293, 428, 493 and 523 K (G3 phase) and 553 and 583 K (G2 phase). The RbLiCrO4 crystals exhibit twinning by merohedry with twin laws in the G3 phase: 2 parallel-to [001], m perpendicular-to [001], 1BAR; in the G2 phase: m parallel-to [001], 2 perpendicular-to [001], 1BAR. The analysis of diffraction intensities and influence of anomalous scattering on them provided the unambiguous determination of the twin laws for all the specimens investigated. The structure has been refined using the approximation of the anharmonic thermal vibrations of atoms.