Effect of off-diagonal elements in the Wannier Hamiltonian on DFT + DMFT for low-symmetry materials: Study of Li 2 MnO 3

Journal Article · 20 November 2023 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.108.205146 · OSTI ID:2345034

Lee, Alex Taekyung  ^[1]; Park, Hyowon ^[1]; Ngo, Anh T. ^[1]

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1. University of Illinois, Chicago, IL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)

Here, we study the effect of the off-diagonal elements of the Wannier Hamiltonian on the electronic structure of the low-symmetry material Li₂MnO₃ (C2/m), using dynamical mean field theory calculations with a continuous-time quantum Monte Carlo impurity solver. The presence of significant off-diagonal elements leads to a pronounced suppression of the energy gap. The off-diagonal elements are largest when the Wannier projection is used based on the global coordinate, and they remain substantial even with the projection using the local coordinate close to the direction of Mn-O bonds. We show that the energy gap is enhanced by the diagonalization of the Mn d block in the full p-d Hamiltonian with the application of a unitary rotation matrix. Additionally, the inclusion of small double counting energy is crucial for achieving the experimental gap by reducing p-d hybridization. Furthermore, we establish the efficiency of a low-energy (d-only basis) model for studying the electronic structure of Li₂MnO₃, as the Wannier basis represents a hybridized state of Mn d and O p orbitals. These findings suggest an appropriate approach for investigating low-symmetry materials using the density functional theory plus dynamical mean field theory (DFT + DMFT) method. We also find that the antiferromagnetic ground state $$\Gamma$$_2u is stable with U ≤ 2 eV within density functional theory+$$U$$ calculations, which is much smaller than the widely used U = 5 eV.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 2345034
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 20 Vol. 108; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English