Laser-Heated Diamond Cell Exposes Stability at Earth's Mantle

Using a laser heating system, a team of scientists at Carnegie Institution of Washington and at the University of Chicago has determined that the rock salt structure of magnesiowüstite is stable at the pressures and temperatures of the Earth's lower mantle. The findings, which appeared in the April 15 issue of PNAS, challenge the hypothesis that the heterogeneity of seismic waves in the lower mantle is the result of a phase transformation of the mineral at the conditions in the lower mantle.

The scientists employed a multimode Nd:YLF laser and a diamond anvil cell at Argonne National Laboratory in Illinois to subject samples to temperatures of up to 2580 K and pressures of up to 102 GPa. Angle-dispersive x-ray diffraction measurements taken with the apparatus indicated that magnesiowüstites are stable in a rock salt structure at these conditions. Previous research using an externally heated diamond anvil cell had indicated that the mineral decomposed into iron- and magnesium-rich components at pressures of 86 GPa and temperatures of 1000 K.