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DFT + U calculations of structural, magnetic, and electrochemical properties and Na<sup>+</sup> diffusion barrier in the O3-phase of NaTm<inf>0</inf><inf>.</inf><inf>5</inf>Ni<inf>0</inf><inf>.</inf><inf>5</inf>O<inf>2</inf> (Tm = Ti, Mn)
Journal
International Journal of Quantum Chemistry
ISSN
00207608
Date Issued
2023-03-05
Author(s)
Kumar, Rahul
Chatterjee, Abhijit
Abstract
O3-type sodium rich layered transition metal (TM) oxides namely NaTm0.5Ni0.5O2 (Tm = Ti, Mn) are theoretically explored in this work. The structural, magnetic and electrochemical properties are studied using first-principles calculations at different Na-intercalation levels. Cell parameters calculated using GGA, GGA + U and dispersion-corrected GGA + U + D3 methods are compared with experimental data. The incorporation of Hubbard parameter (U) for 2p orbital of O with Hubbard parameters of Mn-3d orbitals and Ni-3d orbitals at GGA + U provides a good description of the electronic structure, cell parameter, magnetic moment and effective charge. Comparisons are also made to meta-GGA functional (strongly constrained and appropriately normed) calculations. Ti-based O3-phase is found to be more stable than Mn-based O3-phase for all Na-intercalation levels. However, the presence of Mn ions can significantly reduce the Na+ diffusion barrier as compared to Ti ions in O3-type NaTm0.5Ni0.5O2 system. Both Ti and Mn ions act as structural stabilizers and do not participate in electrochemistry during charge/discharge. PBE + U + D3 functional is recommended to get reliable results for electronic and magnetic properties of these kind of systems.
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