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Published on: May 13, 2020
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The Myth of "Metavalency" in Phase-Change Materials
Robert O Jones1, Stephen R Elliott2, Richard Dronskowski3
1Peter Grünberg Institut PGI-1, Forschungszentrum Jülich, D-52425, Jülich, Germany.
Advanced Materials (Deerfield Beach, Fla.)
|May 10, 2023
Summary
Phase-change memory materials exhibit unique covalent bonds, including multicenter "hyperbonds," challenging the proposed "metavalent bonding" theory. These findings offer new insights into material properties and bonding mechanisms.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Condensed Matter Physics
Background:
- Phase-change memory materials (PCMs) possess unique properties crucial for advanced applications.
- Research into PCMs often focuses on understanding their bonding mechanisms for material improvement.
- The concept of "metavalent bonding" has been proposed as a novel bonding type in PCMs and halide perovskites.
Purpose of the Study:
- To investigate the bonding mechanisms in phase-change memory materials.
- To clarify the nature of bonding in octet-rule-violating PCMs.
- To evaluate the validity of the proposed "metavalent bonding" in PCMs.
Main Methods:
- Theoretical analysis of bonding in phase-change memory materials.
- Examination of electron distribution and bond types.
- Comparison of observed bonding with existing theories.
Main Results:
- Phase-change memory materials exhibit two primary types of covalent bonds: two-center, two-electron (2c-2e) bonds and multicenter bonds (3c-4e, or "hyperbonds").
- These multicenter bonds involve lone-pair electrons and have bond orders less than one, consistent with the concept of partial bonds.
- The findings indicate that the proposed "metavalent bonding" is not a fundamentally new mechanism but rather a description of existing covalent bonding phenomena, specifically partial bonds.
Conclusions:
- The bonding in phase-change memory materials is explained by established covalent bond types, including partial bonds (hyperbonds).
- The concept of "metavalent bonding" does not represent a new bonding mechanism in these materials.
- Understanding these bonding nuances is essential for the development of improved phase-change memory technologies.
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