Antibonding States Drive Anharmonicity and Low Thermal Conductivity in Edge-Sharing Metal Chalcogenides

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Lattice thermal conductivity (κ_L) is a key factor in thermoelectric material performance.
• Stereochemically active lone pairs (SCALPs) and orbital hybridization in edge-sharing polyhedra are known to influence κ_L.

Purpose of the Study:

• To investigate the bonding-driven mechanisms responsible for suppressing lattice thermal conductivity in thermoelectric materials.
• To establish a framework for designing high-performance thermoelectric materials.

Main Methods:

• Utilized machine learning interatomic potentials to simulate and analyze thermal transport.
• Systematically probed bonding characteristics and their correlation with phonon scattering.
• Introduced novel bonding descriptors to quantify anharmonicity.

Main Results:

• Demonstrated that SCALPs, pnictogen-pnictogen (Pn-Pn) bonding, and edge-sharing polyhedra contribute to ultralow κ_L.
• Showed that these factors lead to antibonding states near the valence band maxima, intensifying phonon scattering.
• Validated a set of bonding descriptors (lone pair angle, lone pair distance, ionicity, hybridization) for predicting anharmonicity.

Conclusions:

• The study elucidates the fundamental origins of ultralow lattice thermal conductivity in thermoelectric materials.
• The developed bonding-centric framework provides a rational design strategy for discovering novel high-performance thermoelectric materials.