# Anharmonic inter-layer bonding leads to intrinsically low thermal conductivity of bismuth oxychalcogenides

## TL;DR

This study reveals that electrostatic inter-layer coupling and strong anharmonic chemical bonds in bismuth oxychalcogenides cause intrinsically low thermal conductivity, providing insights into phonon anharmonicity linked to chemical bonding.

## Contribution

The paper establishes a direct connection between inter-layer chemical bonding and phonon anharmonicity using density functional theory calculations.

## Key findings

- Electrostatic inter-layer coupling reduces thermal conductivity.
- Strong anharmonic Bi-chalcogen bonds are responsible for phonon scattering.
- Low thermal conductivity is intrinsic to Bi₂O₂X materials.

## Abstract

The anharmonicity of phonons in solid is ultimately rooted in the chemical bonding. However, the direct connection between phonon anharmoncity and chemical bonding is difficult to make experimentally or theoretically, due mainly to their complicated lattice structures. Here, with the help of density functional theory based calculations, we discovery that electrostatic inter-layer coupling in Bi$_2$O$_2$X (X=S,Se,Te) leads to intrinsically low lattice thermal conductivity. We explain our discovery by the strong anharmonic chemical bonding between Bi and chalcogen atoms. Our results shed light on the connection between inter-layer chemical bonding and phonon anharmonicity, which could be explored in a wide range of layered materials.