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Seo, Dong-Hwa
Computational Energy Materials Science Lab
Research Interests
  • 본 연구실에서는 제일원리 (first-principles) 전산모사 기법을 통해 이차전지용 전극 소재와 고체 전해질 소재에 대해 원자 단위에서 깊이 있게 이해하고 이를 바탕으로 신규 소재를 개발하고 기존 소재의 성능 향상시키는 연구를 진행하고 있습니다. 또한 인공지능 (artificial intelligence)과 기계학습 (Machine learning), 로봇공학 (robotics)을 조합하여 자동 합성/분석을 통한 재료 개발에 대한 연구를 진행하고 있습니다.

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Calibrating transition-metal energy levels and oxygen bands in first-principles calculations: Accurate prediction of redox potentials and charge transfer in lithium transition-metal oxides

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Title
Calibrating transition-metal energy levels and oxygen bands in first-principles calculations: Accurate prediction of redox potentials and charge transfer in lithium transition-metal oxides
Author
Seo, Dong-HwaUrban, AlexanderCeder, Gerbrand
Issue Date
2015-09
Publisher
AMER PHYSICAL SOC
Citation
PHYSICAL REVIEW B, v.92, no.11, pp.115118
Abstract
Transition-metal (TM) oxides play an increasingly important role in technology today, including applications such as catalysis, solar energy harvesting, and energy storage. In many of these applications, the details of their electronic structure near the Fermi level are critically important for their properties. We propose a first-principles-based computational methodology for the accurate prediction of oxygen charge transfer in TM oxides and lithium TM (Li-TM) oxides. To obtain accurate electronic structures, the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional is adopted, and the amount of exact Hartree-Fock exchange (mixing parameter) is adjusted to reproduce reference band gaps. We show that the HSE06 functional with optimal mixing parameter yields not only improved electronic densities of states, but also better energetics (Li-intercalation voltages) for LiCoO2 and LiNiO2 as compared to the generalized gradient approximation (GGA), Hubbard U corrected GGA (GGA+U), and standard HSE06. We find that the optimal mixing parameters for TM oxides are system specific and correlate with the covalency (ionicity) of the TM species. The strong covalent (ionic) nature of TM-O bonding leads to lower (higher) optimal mixing parameters. We find that optimized HSE06 functionals predict stronger hybridization of the Co 3d and O 2p orbitals as compared to GGA, resulting in a greater contribution from oxygen states to charge compensation upon delithiation in LiCoO2. We also find that the band gaps of Li-TM oxides increase linearly with the mixing parameter, enabling the straightforward determination of optimal mixing parameters based on GGA (alpha = 0.0) and HSE06 (alpha = 0.25) calculations. Our results also show that G(0)W(0)@GGA+U band gaps of TM oxides (MO, M = Mn, Co, Ni) and LiCoO2 agree well with experimental references, suggesting that G(0)W(0) calculations can be used as a reference for the calibration of the mixing parameter in cases when no experimental band gap has been reported.
URI
https://scholarworks.unist.ac.kr/handle/201301/30528
URL
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.115118
DOI
10.1103/PhysRevB.92.115118
ISSN
2469-9950
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