Electron Density Changes across the Pressure-Induced Iron Spin Transition

High-pressure single-crystal x-ray diffraction is used to experimentally map the electron-density distribution changes in (Fe,Mg)O as ferrous iron undergoes a pressure-induced transition from high- to low-spin states. As the bulk density and elasticity of magnesiow??stite???one of the dominant mineral phases of Earth???s mantle???are affected by this electronic transition, our results have applications to geophysics as well as to validating first-principles calculations. The observed changes in diffraction intensities indicate a spin-transition-induced change in orbital occupancies of the Fe ion in general accord with crystal-field theory, illustrating the use of electron density measurements for characterizing high-pressure d-block chemistry and motivating further studies characterizing chemical bonding under pressure.

Automated summary

High-pressure single-crystal x-ray diffraction is used to experimentally map the electron-density distribution changes in (Fe,Mg)O as ferrous iron undergoes a pressure-induced transition from high- to low-spin states. Our results have applications to geophysics as well as to validating first-principles calculations, as this electronic transition affects the bulk density and elasticity of magnesiow??stite, one of the dominant mineral phases of Earth's mantle. The observed changes in diffraction intensities indicate a spin-transition-induced change in orbital occupancies of the Fe ion, in line with crystal-field theory.