Ab initio study of the elastic behavior of MgSiO3 ilmenite at high pressure

We investigate the athermal high pressure behavior of the elastic propertie s of MgSiO3 ilmenite up to 30 GPa using the ab initio pseudopotential metho d. Our results at zero pressure are in good agreement with single-crystal e lasticity measurements. The elastic anisotropy is shown to decrease slightl y under compression and hence to remain substantial (25 to 20% shear wave a nisotropy and 16 to 10% longitudinal wave anisotropy) over the pressure reg ime studied. The directions of fastest and slowest wave propagation are fou nd to change slightly with pressure as determined by the pressure dependenc e of c(14) and c(25). Comparisons with the elastic behavior of other deep t ransition zone phases such as ringwoodite and garnet show that ilmenite is likely to be the fastest and most anisotropic mineral in this region. Large contrasts (approximate to 10%) in velocities and densities between ilmenit e and garnet are suggested to be significant for the interpretation of late ral structure in the transition zone.