First-principles study on the ultralow lattice thermal conductivity of BiSeI

Thermoelectric materials have received widespread attention for decades. An important way to find high-efficiency thermoelectric materials is to find materials with ultralow thermal conductivity. Here, we have studied the lattice thermal conductivity of the quasi-one-dimensional semiconductor BiSeI through first-principles calculations. It is found that the thermal conductivity of BiSeI has a large anisotropy due to its quasi-one-dimensional structure. Particularly, BiSeI has ultralow lattice thermal conductivities of 0.28 and 0.34 W/m K along the a and c axes at room temperatures. The lattice thermal conductivity of BiSeI along the b axis is also quite low, which is 1.54 W/m K at room temperatures. It is shown that the quasi-one-dimensional crystal structure and heavy element mass of BiSeI result in low phonon group velocities and short phonon lifetimes, which inevitably lead to ultralow thermal conductivity. Our work implies that BiSeI is a potential thermoelectric material if its electric conductivity could be enhanced in experiments. • First time to study the ultralow lattice thermal conductivity of quasi-one-dimensional semiconductor BiSeI through first-principles calculations. • Calculations show BiSeI is an ultralow thermal conductivity material with extremely anisotropic. • Detailed calculations show that the low phonon group velocities and short phonon lifetimes are the main reasons for the ultralow thermal conductivity of BiSeI.