2021 Fiscal Year Research-status Report
Constraining Earth's Lower Mantle Point Defect Chemistry from the Charge Disproportionation of Iron
| Project/Area Number |
20K14580
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| Research Institution | Ehime University |
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Principal Investigator |
RITTERBEX S 愛媛大学, 地球深部ダイナミクス研究センター, 特定研究員 (00791782)
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Keywords | Ferropericlase / Grain boundaries / Ab initio simulations / Critical shear strength / Ferrous Iron / Spin transition / Plastic deformation / Earth's lower mantle |
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| Outline of Annual Research Achievements |
This year, we have studied the influence of ferrous Fe on the mechanical behavior of tilt grain boundaries in (Mg,Fe)O as a function of pressure. Atomistic simulations were conducted at the supercomputer systems of Nagoya University. Our results show that ferrous iron has a non-unique effect on the critical shear strength of grain boundaries. At pressures lower than 100 GPa, iron has the tendency to increase the critical grain boundary strength, whereas at higher pressures Fe induces a reduction of the critical strength. We also took the influence of the Fe spin state on grain boundary migration into account. We found that a spin transition of Fe in the grain boundary due to shear deformation only occurs in the direct vicinity of the spin transition pressure.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The progress of research related to this grant develops as initially planned. All ab-initio simulations of this year were succesfully conducted at the supercomputer systems of the Information Technology Center at Nagoya University. The resulting data were analyzed at the Geodynamics Research Center of Ehime University. In summary, we were able to conduct our proposed research as planned and are preparing a manuscript on the results obtained in FY2020-2021.
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| Strategy for Future Research Activity |
We will start new computational research to constrain the extent of the Fe spin transition in ferropericlase across the pressure and temperature range of the lower mantle by including crystal imperfections, in particular iron disorder as a function of iron concentration in conjunction with the presence of grain boundaries. It is known that the presence of crystal imperfections influence the thermodynamic properties of minerals, but previous studies ignored these effects which might explain the discrepancy between current mineral physics models and seismic observations on the electronic spin transition of Fe in ferropericlase acrosse the lower mantle.
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| Causes of Carryover |
All initial planned business travels had to be cancelled in FY2021 due to the COVID-19 pandemic. Most conferences were converted into virtual meetings with significantly reduced registration fees. We plan to use the incurring amount in FY2022 on additional computational resources at the Information Technology Center, Nagoya University and on supplementary SSD to support our atomistic simulations and data processing. In addition, we may use the incurring budget for publication fees.
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Research Products
(4 results)
