English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Six single crystals of Mg 3 (Mg x Si x Al 2-2x )Si 3 O 12  with x = 0.05, 0.13, 0.24, 0.38, 0.52, and 0.64 (the majorite solid-solution) were synthesized at 20 GPa and 2000 °C with a “6-8” type uniaxial splitsphere apparatus. Single-crystal X-ray diffraction studies revealed discontinuities in compositional dependence of the molar volume, equivalent isotropic temperature factors (B eq ), and mean bond lengths between x = 0.24 and 0.38. Single crystals in the compositional range 0 ≤ x ≤ 0.24 show no birefringence, whereas those of x = 0.64 have a slight optical anisotropy. Moreover, the cell symmetry for x = 0.64 obtained using synchrotron X-ray radiation is tetragonal with a slight deviation from cubic. On the basis of site splitting expected from compositional dependence of B eq  obtained by cubic refinement, the most probable space group in the range 0.38 ≤ x ≤ 0.64 is I4 1 /acd (tetragonal), which is the maximal subgroup of the space group Ia3̅d (cubic). Given that the previous reports that crystals with 0.8 ≤ x ≤ 1.0 have the tetragonal space group I4 1 /a, the majorite solid-solution in this system undergoes the series of symmetry changes, Ia3̅d →I4 1 /acd→I4 1 /a, with increasing MgSiO 3  component. The symmetry changes from Ia3̅d to I4 1 /acd cannot be explained by the cation ordering on the octahedral site. Strong electrostatic interaction between the dodecahedral (Mg 2+ ) and tetrahedral (Si 4+ ) cations was observed from atomic thermal motion and electron density distribution. Because one of the site symmetries of the two nonequivalent tetrahedral sites in I4 1 /acd structure loses the center of symmetry with the symmetry reduction from Ia3̅d to I4 1 /acd, the symmetry reduction may be caused by the electronic polarization of the cations due to the neighboring cation-cation interaction.

Symmetry change of majorite solid-solution in the system Mg 3 Al 2 Si 3 O 12 -MgSiO 3