2015/03/24 by Gaurav Shukla, Mehmet Topsakal, Shukla, Gaurav +4
Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #Crystal Structures and Properties #FOS: Physical sciences #High-pressure geophysics and materials #Magnetic and transport properties of perovskites and related materials #Materials Science (cond-mat.mtrl-sci) #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.1503.07194
Under Review with Physics of the Earth and Planetary Interiors
arxiv created 2015/03/24 · openalex publication_date 2015/03/24 · arxiv updated 2015/03/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
MgGeO3-perovskite is known to be a low-pressure analog of MgSiO3-perovskite in many respects, but especially in regard to the post-perovskite transition. As such, investigation of spin state changes in Fe-bearing MgGeO3 might help to clarify some aspects of this type of state change in Fe-bearing MgSiO3. Using DFT+U calculations, we have investigated pressure induced spin state changes in Fe2+ and Fe3+ in MgGeO3 perovskite and post-perovskite. Owing to the relatively larger atomic size of germanium compared to silicon, germanate phases have larger unit cell volume and inter-atomic distances than equivalent silicate phases at same pressures. As a result, all pressure induced state changes in iron occur at higher pressures in germanate phases than in the silicate ones, be it a spin state change or position change of (ferrous) iron in the perovskite cage. We showed that iron state transitions occur at particular average Fe-O bond-length irrespective of mineral composition (silicate or germanate) or functionals (LDA+Usc or GGA+Usc). Ferrous iron substitution decreases the perovskite to post-perovskite (PPv) transition pressure while coupled ferric iron substitution increases it noticeably.