First-principles study of phonon thermal transport in II–VI group graphenelike materials

Abstract

Using the first-principles calculations and combining with the phonon Boltzmann transport equation, we systematically investigated the phonon thermal transport properties of II–VI group graphenelike materials (BeO, MgO, CaO, SrS, and SrSe). The lattice thermal conductivities κL’s of 118.68, 42.48, 11.13, 3.33, and 3.09 W/mK are obtained at 300 K in BeO, MgO, CaO, SrS, and SrSe, respectively, which is much lower than that of graphene. Strikingly, the κL of SrS and SrSe is lower than most two-dimensional materials. Further analyses revealed that (i) the lower phonon group velocity of SrS and SrSe caused by a larger atomic mass reduces the κL and (ii) strong anharmonicity and more available phonon scattering channels enhance phonon anharmonic scattering, resulting in lower κL. By means of the relationship between κL and the phonon mean-free path and the width of nanowires, the size dependence of lattice thermal conductivity is investigated as well, which provides a theoretical basis for the design of thermoelectric nanostructures.