The crystal structure of KCdF3

Abstract

The crystal structure of KCdF3 is determined in the third, orthorhombic phase and refined by using a full matrix least-squares method by taking domain structures into consideration. Refinement is performed with superlattice-X, M and R point reflection intensity data collected on the multiple-film Weissenberg photographs taken with filtered MoKα radiation. Pbnm-D16 2h (z = 4) is assigned to the space group of KCdF3. The R value reaches 8 % for the intensity data of the X and M point reflections. When the R point reflections are included in the calculation, the R value is 9.8 %. The structure is well described by the successive condensations of M3 and Z5 (Rx25 + Ry 25-like) soft-phonon modes

Study of Structural Phase Transitions of KCaF3

“…Some kinds of superlattice reflections are observed at room temperature by the structural transitions. The structure in phase I11 was determined to be of orthorhombic symmetry D;:-Pbnm regarding the population ratio of poly-domains in the used single crystal [4]. By indexing the reflections, the superlattice reflections were confirmed to be a t the GI CH SH AS SP TB GH TE MI, R-, and X-points in the reciprocal space.…”

Crystal structure and bonding in transition-metal fluoro compounds

“…Na6Al3F14 (150,152) chiolites Framework Structures type example AMF3: perovskites NaNiF3, NaCuF3 (154)(155)(156), K4Mn3F12 (164) AxMF3: bronzes KMF3, KCuF3 (157)(158)(159)(160)(161)(162)(163), Cs2Ba2Cu3F12 (127,164) K06FeF3 TTB (165,166) AIMIIMlnF6: pyrochlores CSo 2Zn02Fe0 gF3 HTB (167,168) FeF3-0.33H2O HTB (169) RbNiCrF6 (67,170,171) AI2MuMmF7: weberites CsAgFeF6, NH4Fe2F6 (172-174)…”

First‐principles study of NaCdF3

“…We found that for the band structure calculations, 101 k-points were enough to obtain good results. For the optical calculations, however, the irreducible Brillouin zone was sampled with 1000 k-points for NaCdF 3 .…”

“…However, several alkaline earth cadmium trifluoride compounds, MCdF 3 (M = K, Rb, Cs), have been synthesized experimentally which have not exhibited ferroelectricity [3,4]. In the predicted ferroelectric phase, NaCdF 3 has a rhombohedral structure with two NaCdF 3 molecules (ten atoms) per unit cell.…”