2020 Fiscal Year Research-status Report
Testing and enhancement of computational DFT+U method with magnetic exchange correction
| Project/Area Number |
18K05031
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| Research Institution | Kyoto University |
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Principal Investigator |
Shishkin Maxim 京都大学, 実験と理論計算科学のインタープレイによる触媒・電池の元素戦略研究拠点ユニット, 特定研究員 (20793011)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Keywords | DFT+U / redox potentials / opposite spins |
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| Outline of Annual Research Achievements |
In this year the extended DFT+U method (DFT+U with additional corrections of interactions between the electrons with opposite spins), formulated in the initial stages of this project has been applied for calculation of redox potentials of several important cathode materials. Important new result is a proposed computational procedure, which allows parameterisation of the extended DFT+U method, providing numerically determined values of a standard U parameter as well as additional U parameter, used for description of interactions between the electrons with opposite spins.
The calculations provided a very good agreement of theoretical values of redox potentials as compared to experimental measurements, fully avoiding fitting to previously found experimental results. It was also demonstrated that the standard method of Lichtenstein et al does not provide improvement in prediction of values of redox voltages, in spite of a formal inclusion of corrections of interactions between the electrons with opposite spins. Moreover, it has been shown that corrections of exchange interactions (setting J parameter) results only in a very minor change of calculated redox potentials.
Additionally, calculations of a full voltage profile of NaMnO2 material has been completed, also in a very good agreement with experiment and without recourse to measured data. Overall, it has been demonstrated that proposed extension of DFT+U method could be used for calculations of redox voltages of a wide range of cathode materials as well as for voltage profile evaluation.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Due to Corona restrictions, several scientific visits could not be organised or should be cancelled.
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| Strategy for Future Research Activity |
It is planned to apply the proposed extended functional (DFT+U with additional corrections of interactions between the electrons with opposite spins) to the study of energies of formation of several important transition metal oxides. Preliminary tests show that linear response approach is not suitable for this task, however extended functional with adjusted additional parameters could provide accurate values for energies of formation as well as for magnetic moments (not possible with standard DFT+U). A possible impact of exchange correlation functional (PBE vs. SCAN) will be studied and attempts to parameterise calculations computationally will be made. Explanations as to why DFT+U/linear response method does not provide accurate values of formation energy will be sought.
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| Causes of Carryover |
Several visits and conferences have been canceled due to Corona virus.
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