Multi?Center Hyperbonding in Phase?Change Materials

A comprehensive understanding of chemical interactions underlying the network structure chalcogenide materials is a crucial prerequisite for comprehending their microscopic structures, physicochemical properties, and capabilities current or potential applications. However, many materials, an inherent difficulty often present in investigating due to involvement delocalized bonding non-bonding (“lone-pair”) electrons, which requires interaction mechanisms beyond that conventional two-center, two-electron covalent bonding. Herein, some recent progress development new interatomic models chalcogenides reviewed, particular focusing on multi-center hyperbonding model, proposed effort resolve this issue. The capability model elucidating diversity interesting material properties phase-change (PCMs) highlighted, including Ge2Sb2Te5 (GST). These include propensity high coordination numbers constituent atoms, linear triatomic geometries with short long bonds (often ascribed effect Peierls distortion), abnormally large Born effective charges crystalline GST, optical contrast between amorphous ultrafast crystallization speed origin differentiating non-PCM from PCM materials. Other these are also briefly discussed.