Reduction of thermal conductivity by low energy multi-Einstein optic modes

The lattice dynamics and thermal transport in Cu2-δSe compounds were investigated via theoretical calculations, neutron measurement, and characterization of thermal properties. The results show that binary ordered Cu2-δSe has an extremely low lattice thermal conductivity at low temperatures. The low energy multi-Einstein optic modes are the dominant approach obtaining such an extremely low lattice thermal conductivity. It is indicated that the damped vibrations of copper ions could contribute to the low energy multi-Einstein optic modes, especially for those low energy branches at 2–4 meV.

Graphical abstractThe copper-based thermoelectric Cu2-δSe compound shows extremely low lattice thermal conductivity. The lattice thermal conductivity and heat capacity were analyzed, and the inelastic neutron scattering measurements and ab initio lattice dynamic calculation were performed to demonstrate the low energy multi-Einstein optic-like vibrations, which dominate the reduction of the lattice thermal conductivity in this compound.Figure optionsDownload full-size imageDownload as PowerPoint slide