X-ray diffraction and Mossbauer spectroscopy of Fe3+-bearing Mg-silicate post-perovskite at 128-138 GPa

The effect of ferric iron oil the properties of Mg-silicate post-perovskite (PPv) were studied Up to 138 GPa using synchrotron X-ray diffraction and Mossbauer spectroscopy. Our diffraction Measurements revealed that the incorporation of Fe3+ has virtually no effect oil the volume of PPv,, in contrast to Fe2+, which increases the volume. Therefore, incorporation of Fe3+ increases the density of PPv much more effectively than Fe. Mossbauer spectroscopy suggests that Fe3+ enters PPv through charge-coupled Substitution and is high spin ill the bipolar prismatic site and low spin in the octahedral site (i.e., mixed spin state). Our results may have important implications I'm the gravitational stability of lower-mantle heterogeneities.