Revisiting the Crystal Structure of Layered Oxychalcogenides LnOS (Ln = La, Pr, and Nd).

LaOS was recently used as a precursor to prepare either a new metastable form of LaOS by de-insertion of half of sulfur atoms of (S) dimers or quaternary compounds by insertion of a coinage metal (e.g., LaOCuS).

Solvothermal and mechanochemical intercalation of Cu into LaOS enabled by the redox reactivity of (S) pairs.

Intercalation of Cu into layered polychalcogenide LaOS was demonstrated to be viable both under solvothermal conditions at 200 °C and mechanical ball milling at ambient temperature. This result evidences the soft-chemical nature of metal intercalation into layered polychalcogenides driven by the redox reactivity of anion-anion bonds.

Design of metastable oxychalcogenide phases by topochemical (de)intercalation of sulfur in LaOS.

Designing and synthesising new metastable compounds is a major challenge of today's material science. While exploration of metastable oxides has seen decades-long advancement thanks to the topochemical deintercalation of oxygen as recently spotlighted with the discovery of nickelate superconductor, such unique synthetic pathway has not yet been found for chalcogenide compounds. Here we combine an original soft chemistry approach, structure prediction calculations and advanced electron microscopy techniques to demonstrate the topochemical deintercalation/reintercalation of sulfur in a layered oxychalcogenide leading to the design of novel metastable phases.

Prediction of a New Layered Polymorph of FeS with FeS(S) Structure.

The never-elucidated crystal structure of metastable iron disulfide FeS resulting from the full deintercalation of Li in LiFeS has been cracked thanks to crystal structure prediction searches based on an evolutionary algorithm combined with first-principles calculations accounting for experimental observations. Besides the newly layered 2/ polymorph of iron disulfide, two-dimensional dynamically stable FeS phases are proposed that contain sulfides and/or persulfide S motifs.