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PRINCIPAL PUBLICATION AND AUTHORS
Untangling the Mechanisms of Lattice Distortions in Biogenic Crystals across Scales, V. Schoeppler (a,b), P.K. Cook (c), C. Detlefs (c), R. Demichelis (d), I. Zlotnikov (a), Adv. Mater. 34, 28, 2200690 (2022); https:/doi.org/10.1002/adma.202200690 (a) B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden (Germany) (b) Department of Physics, University of California (USA) (c) ESRF (d) Curtin Institute for Computation, The Institute for Geoscience Research (TIGeR), School of Molecular and Life Sciences, Curtin University, Perth (Australia)
of calcite in the prisms, specifically the back and forth rotation around the <10 10> axis, is accompanied by local changes in the lattice parameters of calcite.
The DFXM data enables the behaviour of the lattice to be characterised using the two chosen rotation axes: [10 10] and [1 210]. Most importantly, the selection of these specific directions makes it possible to deconvolute two types of lattice distortions. The analysis of the two orthogonal datasets yielded clear interpretation of the measured crystallographic properties of biogenic calcite in the prisms of P. nobilis. During growth, the organic molecules are incorporated on the basal plane of calcite. As a result, periodic changes in organic and inorganic impurities cause alternating anisotropic lattice distortions and inter-planar spacing. Furthermore, the entire calcific lattice, as described by the persistent bending of the
c-axis, gradually rotates around the [1 210]-axis, which is perpendicular to one of the main slip directions of calcite.
By using DFXM, it was possible to put local crystallographic variations of biogenic calcite into the perspective of the formation of the entire ultrastructure. DFXM measurements yielded 3D information on the evolution of morphological (macroscale) and local crystallographic (nanoscale) properties of the biomineral during growth with high spatial and angular resolution. Ultimately, careful analysis of the obtained data made it possible to identify mechanisms that are responsible for the convoluted lattice behaviour across scales and in 3D. It is thought that this experimental approach will become key not only in the study of synthetic and geological materials systems, but also in biological materials and biomineralisation research.
Materials synthesis at terapascal static pressures
The synthesis and investigation of materials at ultra-high pressures have been hindered by the technical complexity of experiments and the absence of relevant methods of material analysis in situ. A new methodology using X-ray diffraction and a novel diamond anvil cell has been developed and its capabilities have been demonstrated on Re-N compounds at terapascal pressure.
The state of matter is strongly affected by its chemical composition and external parameters such as pressure and temperature. Varying these allows a material s properties to be tuned. Compression is known to endorse, for example, metal-to-insulator transitions, superconductivity and other interesting phenomena. To generate very high static pressures, a diamond anvil cell (DAC) is used. This is an instrument in which the material under investigation is squeezed between the very small flat tips of two gem- quality diamonds. Due to the extremely high compressional strength of diamond, pressures up to ~300 GPa (3 million atmospheres) can be achieved on the sample if the diameter of the diamond anvils is of 40 µm.
The latest developments in the diamond anvil cell technique and, particularly, the invention of double-stage and toroidal diamond anvil cells (ds-DACs and t-DACs), have enabled a breakthrough in the synthesis of materials such as novel transition metals, nitrides and polynitrides including metal-inorganic frameworks (a new class of compounds featuring open porous structures at megabar compression), and in studying structure-property relations at high and ultra-high pressures.
Solving and refining the crystal structures of solids synthesised directly from elements in laser-heated, conventional DACs at pressures as high as up to two megabar has become possible due to increasing expertise both in generating multimegabar pressures and in single- crystal X-ray diffraction at ultra-high pressures.
Whereas high-pressure-high-temperature synthesis is a well-established technique for materials discovery, extending investigations to the TPa regime has been desired for a long time. The task presented challenges, as it required a considerable decrease in the size of the diamond tips and super-strong materials in the design of the DAC to allow it to sustain such enormous pressures.