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

Dong Hwa Seo, Alexander Urban, Gerbrand Ceder*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Citations (Scopus)

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 Co3d and O2p 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 (α=0.0) and HSE06 (α=0.25) calculations. Our results also show that G0W0@GGA+U band gaps of TM oxides (MO,M=Mn,Co,Ni) and LiCoO2 agree well with experimental references, suggesting that G0W0 calculations can be used as a reference for the calibration of the mixing parameter in cases when no experimental band gap has been reported.

Original languageEnglish
Article number115118
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume92
Issue number11
DOIs
Publication statusPublished - 8 Sept 2015

Fingerprint

Dive into the research topics of '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'. Together they form a unique fingerprint.

Cite this