Thermal Conductivity of Rutile and Anatase TiO2 from First-Principles

We compute the thermal conductivity of the most common polymorphs of titanium dioxide (TiO2), rutile and anatase, using a first-principles A approach and solving the phonon Boltzmann transport equation beyond the relaxation time approximation. We find that both polytypes are anisotropic, as expected from their crystal structure; however, while kappa(xx) = kappa(yy) < kappa(zz) for rutile, the opposite holds for anatase. The modal decomposition of the thermal conductivity provides insight in this inversion in the anisotropy of the two polytypes.