2022 Fiscal Year Research-status Report
Extended DFT+U method: application to analysis of complex doping effects, methodological developments and materials design.
| Project/Area Number |
22K05019
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
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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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | DFT+U / redox potentials / opposite spins |
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| Outline of Annual Research Achievements |
During the last year the newly proposed extension of DFT+U method with corrections for interactions between the electrons with opposite spins (absent in standard DFT+U) has been applied for the study of energies of formation of transition metal oxides and voltage profiles of complex battery cathodes that contain two types of active redox centers.
Detailed tests revealed that energies of formation could be calculated by setting of magnetic moments close to experimental values by the newly introduced correction term. Linear response method was found not accurate for this task. Moreover tests have shown superiority of SCAN functional over PBE. Thus the methodology for evaluation of formation energies of transition metal oxides has been formulated. Tests have been performed for Mn, Fe, V and Cr oxides, yielding a good agreement with experiment for energies of formation and magnetic moments.
The extended DFT+U method has been also applied for the study of electrochemical properties of a layered oxide structure, which contains two types of transition metals (Ni and Mn). This method provided very promising and accurate prediction of the voltage profile in a good agreement with experimental measurements. A robust form of evaluation of the U parameters has been proposed for the standard DFT+U method as well.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Preliminary tests of calculations of a voltage curve of Cu doped NaMnO2 has shown a somewhat poor agreement with experimental measurements. After thorough analysis it was found that long range effects are very important for analysis of the cathode at low level of doping (12.5% of Cu). However, very large cells would be needed for analysis of a de-intercalation in such a structure (to account for long range effects). This makes calculations computationally prohibitive. Therefore alternative structures have been searched for testing of the proposed method. Similarly NASICON structures would require very large cells. A possible solutions to allow for a computational study is under a search.
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| Strategy for Future Research Activity |
It is planned to study voltage profiles for various phases of LiNiMnO2 structures, including both layered oxides and spinels. A possibility of addressing of Li0.5MnCrO2 spinel structures are also considered. The role of exchange effects will be studied too using materials that contain large charges in both spin channels.
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| Causes of Carryover |
The computational clusters (Xeon machines) have been purchased last year. Installation of required software has been performed (e.g. compiles, math libraries, MPI, etc). In the coming year a cluster of a similar model will be purchased. Due to an increased cost for a computational hardware, attendance of conferences is likely to happen only remotely.
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