We calculate the lattice thermal conductivity ($\kappa$) for cubic (zinc-blende) and hexagonal (wurtzite) phases for 8 semiconductors using $\textit{ ab initio}$ calculations and solving the Phonon Boltzmann Transport Equation, explaining the different behavior of the ratio $\kappa_{ \rm hex}/\kappa_{ \rm cub}$ between the two phases. We show that this behavior depends on the relative importance of two antagonistic factors: anharmonicity, which we find to be always higher in the cubic phase; and the accessible phase space, which is higher for the less symmetric hexagonal phase. Based on that, we develop a method that predicts the most conducting phase---cubic or hexagonal---where other more heuristic approaches fail. We also present results for nanowires made of the same materials, showing the possibility to tune $\kappa_{ \rm hex}/\kappa_{ \rm cub}$ over a wide range by modifying their diameter, thus making them attractive materials for complex phononic and thermoelectric applications/systems.
Categories: cond-mat.mtrl-sci