Acta Crystallographica Section B

The change in symmetry at the Verwey transition in magnetite puts it in an important class of phase transitions with linear/quadratic coupling between two separate order parameters. We use group theory to characterize the form of the coupling between charge order and an electronic instability, and test the model with structural data.

The extended Zintl–Klemm concept (EZKC), applied satisfactorily to rationalize the structures aluminates and silicates, also accounts for the structures of ternary phosphonitrides.

Seven ammonium salts of hypodiphosphoric acid, H₄P₂O₆, are described in terms of their crystal structure, phase transitions, dehydration and decomposition using SC-XRD, variable-temperature µ-PXRD, differential scanning calorimetry and simultaneous thermogravimetry and differential thermal analysis.

Single-crystal X-ray diffraction is used to characterize the role of the solvent molecule in the crystal packing of three new hydrated salts formed from ethacridine and fluorobenzoic acids. The number of water molecules in the asymmetric unit determines the formation of distinct centrosymmetric supramolecular synthons: […water…acid…]₂ and […water…water…acid…]₂

The structure of unique compound Cs₄Ca[Si₈O₁₉] reported recently by Kahlenberg [(2025), Acta Cryst. B81, 325–336] contributes to the broader understanding of structure–property relationships in open-framework silicates (as well as silicates with mixed octahedral–tetrahedral frameworks), with potential implications for ion-exchange, catalysis, and materials with tailored thermal expansion.