Definides

Definides are a proposed class of inorganic crystalline materials defined by dual, independently tunable subsystems embedded within a single lattice. The name (plural definides) derives from the concept of definable electronic or magnetic states that can be controlled separately within the material.

Structure and composition: Definides are envisioned as layered or cluster-based frameworks in which two subsystems coexist: a conductive framework and an orbitally active block, coupled weakly, enabling independent modification of charge transport and local magnetism or optical properties. The materials are often described as derivatives of van der Waals–bonded structures, with chemical formulations loosely represented as A-B2-X4 or M2X3-type families, though exact compositions vary.

Synthesis and status: As a concept, definides have been explored primarily in theoretical and computational studies. A handful of experimental reports claim formation of prototype definide-like phases under specialized high-pressure, high-temperature, or solvothermal conditions, but reproducibility and stability remain under debate.

Properties and potential applications: The core appeal of definides lies in tunable multifunctionality—possible applications include neuromorphic computing, memory devices, optoelectronics, and catalysis. They are studied for potential anisotropic transport, switchable magnetic order, and adaptable optical gaps.

Challenges and outlook: Key obstacles are achieving robust phase stability, scalable synthesis, and precise control over the coupled subsystems. If realized, definides would expand the family of quantum materials and layered dielectrics.

See also: quantum materials, van der Waals materials, perovskites.