The elastic constants of MgSiO3 perovskite at pressures and temperatures of the Earth's mantle

The temperature anomalies in the Earth's mantle associated with thermal con vection(1) can be inferred from seismic tomography, provided that the elast ic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obt ain directly through laboratory experiments. We have therefore taken advant age of recent advances in computer technology, and have performed finite-te mperature ab initio molecular dynamics simulations(2,3) of the elastic prop erties of MgSiO3 perovskite, the major mineral of the lower mantle, at rele vant thermodynamic conditions. When combined with the results from tomograp hic images of the mantle, our results indicate that the lower mantle is eit her significantly anelastic(4) or compositionally heterogeneous on large sc ales(5). We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800 K at 1,000 km, 1,5 00 K at 2,000 km, and possibly over 2,000 K at the core-mantle boundary.