ic7b01926_si_001.pdf (570.82 kB)
Denticity and Mobility of the Carbonate Groups in AMCO3F Fluorocarbonates: A Study on KMnCO3F and High Temperature KCaCO3F Polymorph
journal contribution
posted on 2017-10-18, 19:12 authored by Gwenaelle Rousse, Hania Ahouari, Vladimir Pomjakushin, Jean-Marie Tarascon, Nadir Recham, Artem M. AbakumovWe report on a thorough
structural study on two members of layered fluorocarbonates KMCO3F (M = Ca, Mn). The Ca-based member demonstrates a phase transition
at ∼320 °C, evidenced for the first time. The crystal
structure of the high temperature phase (HT-KCaCO3F) was
solved using neutron powder diffraction. A new Mn-based phase KMnCO3F was synthesized, and its crystal structure was solved from
electron diffraction tomography data and refined from a combination
of X-ray synchrotron and neutron powder diffraction. In contrast to
other members of the fluorocarbonate family, the carbonate groups
in the KMnCO3F and HT-KCaCO3F structures are
not fixed to two distinct orientations corresponding to mono- and
bidentate coordinations of the M cation. In KMnCO3F, the
carbonate group can be considered as nearly “monodentate”,
forming one short (2.14 Å) and one long (3.01 Å) Mn–O
contact. This topology provides more flexibility to the MCO3 layer and enables diminishing the mismatch between the MCO3 and KF layers. This conclusion is corroborated by the HT-KCaCO3F structure, in which the carbonate groups can additionally
be tilted away from the layer plane thus relieving the strain arising
from geometrical mismatch between the layers. The correlation between
denticity of the carbonate groups, their mobility, and cation size
variance is discussed. KMnCO3 orders antiferromagnetically
below TN = 40 K.
History
Usage metrics
Categories
Keywords
HT-KCaCO 3 F structureKMnCO 3 orders antiferromagneticallyneutron powder diffractionHT-KCaCO 3 F structuresHT-KCaCO 3 FMCO 3 layerMn-based phase KMnCO 3 Fcarbonate groupsAMCO 3 F FluorocarbonatesmismatchKFcrystal structureelectron diffraction tomography dataKMnCO 3 Fmembercation size variancefluorocarbonates KMCO 3 FHigh Temperature KCaCO 3 F Polymorph
Licence
Exports
RefWorks
BibTeX
Ref. manager
Endnote
DataCite
NLM
DC