| 研究課題/領域番号 |
22K05019
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| 研究機関 | 東京工業大学 |
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研究代表者 |
Shishkin Maxim 東京工業大学, 科学技術創成研究院, 特任助教 (20793011)
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| 研究期間 (年度) |
2022-04-01 – 2025-03-31
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| キーワード | DFT+U / redox potentials / opposite spins / formation energies |
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| 研究実績の概要 |
The novel extended DFT+U method that includes corrections for interactions between the electrons with opposite spins has been applied for analysis of formation energies, magnetic moments and the band gaps of typical 3d transition metal oxides. Tests have shown that adjustment of magnetic moments of transition metals, particularly Mn and Fe in the oxides where high oxidation state is present (MnO2 and Fe2O3) using the proposed extension of DFT+U could indeed result in improved values for magnetic moments and also for energies of formation.
For materials where magnetic moments are determined with a reasonable accuracy by SCAN functional (e.g. V oxides), it was found that a better agreement could be achieved via correction of the band gaps (these were also not so accurate when evaluated by SCAN calculations).
In addition, the voltage profiles of cathode materials have been calculated with particular emphasis on cathode materials that contain two types of 3d transition metals. LiNi0.25Mn0.75O2 has been selected as a test structure due to availability of experimental measurements. It was found that the scheme, previously proposed by the applicant for determination of U parameters needed to be adjusted for the structure that contain two types of transition metals as the magnetic moments of Ni cations are significantly underestimated as compared to experiment. For this reason, an alternative scheme has been proposed for structures with two types of transition metals (Ni and Mn) yielding more accurate evaluation of magnetic moments.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
Attempts have been made to evaluate the U parameters computationally for evaluation of energies of formation of transition metal oxides. However, these tests were not successful. It was decided to rely on a fitting approach for evaluation of magnetic moments and energies of formation.
The voltage profiles of cathodes with two types of transition metals were difficult to evaluate due to a very large size of computational cells required for a good convergence.
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| 今後の研究の推進方策 |
It is planned to complete the evaluation of energies of formation of all 3d transition metals and possibly other types of transition metals. Also formation energies of compounds with several types of transition metals will be studied.
Effects of dopants on stabilisation of cathode materials will be studied too. This will include complex structures with two types of redox active transition metals.
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| 次年度使用額が生じた理由 |
The new equipment will be bought in the next research period. The additional massive calculations should be carried out as a part of this project. Particularly, the time consuming calculations of voltage profiles needs to be performed.
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