Title: Thermal conductivity changes across a structural phase transition: the case of high-pressure silica,
Abstract: By means of first-principles calculations, we investigate the thermal
properties of silica as it evolves, under hydrostatic compression, from a
stishovite phase into a CaCl$_2$-type structure. We compute the thermal
conductivity tensor by solving the linearized Boltzmann transport equation
iteratively in a wide temperature range, using for this the pressure-dependent
harmonic and anharmonic interatomic couplings obtained from first principles.
Most remarkably, we find that, at low temperatures, SiO$_2$ displays a large
peak in the in-plane thermal conductivity and a highly anisotropic behavior
close to the structural transformation. We trace back the origin of these
features by analyzing the phonon contributions to the conductivity. We discuss
the implications of our results in the general context of continuous structural
transformations in solids, as well as the potential geological interest of our
results for silica.