The Orbital Origins of Chemical Bonding in Ge−Sb−Te Phase‐Change Materials

• Published in: Angewandte Chemie International Edition Vol. 61; no. 17; pp. e202115778 - n/a
• Main Authors: Hempelmann, Jan, Müller, Peter C., Ertural, Christina, Dronskowski, Richard
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 19.04.2022; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Antimony; Chemical bonds; Data storage; Material properties; Metavalent Bonding; Multicenter Bonding; Phase-Change Materials; Tellurium; Wave functions; Wavefunction Analysis; Metavalent Bonding; Multicenter Bonding; Wavefunction Analysis; Phase-Change Materials
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202115778

Layered phase‐change materials in the Ge−Sb−Te system are widely used in data storage and are the subject of intense research to understand the quantum‐chemical origin of their unique properties. To uncover the nature of the underlying periodic wavefunction, we have studied the interacting atomic orbitals including their phases by means of crystal orbital bond index and fragment crystal orbital analysis. In full accord with findings based on projected force constants, we demonstrate the role of multicenter bonding along straight atomic connectivities. While the resulting multicenter bonding resembles three‐center‐four‐electron bonding in molecules, its solid‐state manifestation leads to distinct long‐range consequences, thus serving to contextualize the material properties usually termed “metavalent”. Eventually we suggest multicenter bonding to be the origin of their astonishing bond‐breaking and phase‐change behavior, as well as the too small “van‐der‐Waals” gaps between individual layers. Wavefunction analysis of phase‐change materials in terms of interacting atomic orbitals reveals the decisive role of electron‐rich multicenter interactions, similar yet different from the molecular case. The rather uncommon properties of these phases such as bond‐breaking behavior and other structural peculiarities arise as a natural consequence of electron‐rich multicenter bonding in condensed matter.