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Towards a Single Chemical Model for Understanding Lanthanide Hexaborides
Julen Munarriz1, Paul J Robinson2, Anastassia N Alexandrova1,3
1Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, 90095, USA.
Angewandte Chemie (International Ed. in English)
|October 5, 2020
Summary
A new dynamic bonding model explains diverse lanthanide hexaboride properties by considering covalent and alternative bonding states influenced by electron-phonon coupling. This unifies understanding of materials like EuB6, YbB6, and LaB6.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Chemistry
Background:
- Lanthanide hexaborides (LnB6) exhibit diverse and anomalous properties despite similar crystal and electronic structures.
- The origin of this property variation, including mixed valency, superconductivity, and phase transitions, remains unclear.
- Previous models have focused on specific compounds, lacking a unifying framework for the LnB6 family.
Purpose of the Study:
- To develop a unifying dynamic bonding model for lanthanide hexaborides.
- To explain the diverse properties observed across different LnB6 compounds, including EuB6, YbB6, and LaB6.
- To elucidate the role of covalent bonding and electron-phonon coupling in dictating LnB6 material properties.
Main Methods:
- Building upon a prior model for SmB6.
- Developing a dynamic bonding model incorporating covalent and alternative bonding states.
- Analyzing the influence of electron-phonon coupling on bonding accessibility and energetics.
Main Results:
- The dynamic bonding model successfully explains the distinct properties of EuB6, YbB6, and LaB6 within a single framework.
- Demonstrated that lanthanide elements can form covalent bonds with boron in LnB6.
- Showcased that electron-phonon coupling facilitates access to alternative bonding states in some LnB6 compounds.
- Established that the nature, energetics, and accessibility of these bonding states determine the material properties.
Conclusions:
- A unified dynamic bonding model provides a comprehensive explanation for the diverse properties of lanthanide hexaborides.
- The interplay between covalent bonding, alternative bonding states, and electron-phonon coupling is crucial for understanding LnB6 behavior.
- This model offers a new perspective for predicting and designing LnB6 materials with tailored properties.
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