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25 juin 2019

Stacking sequence variations in vaterite resolved by precession electron diffraction tomography using a unified superspace model

Vaterite : a 60-years long conundrum resolved using electron tomography. Vaterite, the least stable crystalline polymorph of CaCO3, is involved in the first step of crystallization of several carbonate-forming systems including the two stable polymorphs calcite and aragonite. Its complete structural determination consequently sheds important light to understand scaling formation and biomineralization processes. While vaterite’s hexagonal structure approximant was determined by Kamhi 60 years ago, no model up to now was able to satisfactorily account for all the signatures visible in the diffraction patterns. Using electron diffraction tomography at the single crystal scale, such diffraction signatures could be interpreted using periodic and aperiodic modulated structures, depending on temperature, resolving one of the longest structural enigma.
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Contact : Daniel Chateigner