Unexpected Ge–Ge Contacts in the Two‐Dimensional Ge4Se3Te Phase and Analysis of Their Chemical Cause with the Density of Energy (DOE) Function

A hexagonal phase in the ternary Ge–Se–Te system with an approximate composition of GeSe_0.75Te_0.25 has been known since the 1960s but its structure has remained unknown. We have succeeded in growing single crystals by chemical transport as a prerequisite to solve and refine the Ge₄Se₃Te structure. It consists of layers that are held together by van der Waals type weak chalcogenide–chalcogenide interactions but also display unexpected Ge–Ge contacts, as confirmed by electron microscopy analysis. The nature of the electronic structure of Ge₄Se₃Te was characterized by chemical bonding analysis, in particular by the newly introduced density of energy (DOE) function. The Ge–Ge bonding interactions serve to hold electrons that would otherwise go into antibonding Ge–Te contacts.