First-principles study on ultralow lattice thermal conductivity in HfGeTe4

Abstract

Materials with ultralow lattice thermal conductivity have attracted considerable interest in thermoelectrics and thermal management. Here, we have studied the lattice thermal conductivities in the layered material, hafnium germanium tetratelluride HfGeTe4, by the first-principles calculations and revealed an ultralow out-of-plane lattice thermal conductivity of [Formula: see text] at 300 K. HfGeTe4 also had a large anisotropy in its lattice thermal conductivities, and the [Formula: see text]/[Formula: see text] ratio reached as high as 10.4 at 300 K. By analyzing its phonon dispersion, group velocities, and lifetimes, we find that the ultralow lattice thermal conductivity of HfGeTe4 was mainly due to the small group velocities and short lifetimes of phonons, which was essentially caused by its heavy elements and complex layered crystal structure. Considering that HfGeTe4 is a semiconductor with a moderate band gap, HfGeTe4 would be a potential thermoelectric material. Our work sheds light on future studies on the thermoelectric properties of HfGeTe4.