First-principles determination of elastic anisotropy and wave velocities of MgO at lower mantle conditions

The individual elastic constants of magnesium oxide (MgO) have been determi ned throughout Earth's Lower mantle (LM) pressure-temperature regime with d ensity functional perturbation theory. It is shown that temperature effects on seismic observables (density, velocities, and anisotropy) are monotonic ally suppressed with increasing pressure. Therefore, at realistic LM condit ions, the isotropic wave velocities of MgO remain comparable to seismic vel ocities, as previously noticed in athermal high-pressure calculations. Also , the predicted strong pressure-induced anisotropy is preserved toward the bottom of the LM, so lattice-preferred orientations in MgO may contribute s ubstantially to the observed seismic anisotropy in the D " Layer.