Hybrid density functional calculations of redox potentials and formation energies of transition metal compounds

Abstract

We compare the accuracy of conventional semilocal density functional theory ͑DFT͒, the DFT+ U method, and the Heyd-Scuseria-Ernzerhof ͑HSE06͒ hybrid functional for structural parameters, redox reaction energies, and formation energies of transition metal compounds. Conventional DFT functionals significantly underestimate redox potentials for these compounds. Zhou et al. ͓Phys. Rev. B 70, 235121 ͑2004͔͒ addressed this issue with DFT+ U and a linear-response scheme for calculating U values. We show that the Li intercalation potentials of prominent Li-ion intercalation battery materials, such as the layered Li x MO 2 ͑M = Co and Ni͒, Li x TiS 2 ; olivine Li x MPO 4 ͑M = Mn, Fe, Co, and Ni͒; and spinel-like Li x Mn 2 O 4 , Li x Ti 2 O 4 , are also well reproduced by HSE06, due to the self-interaction error correction from the partial inclusion of Hartree-Fock exchange. For formation energies, HSE06 performs well for transition metal compounds, which typically are not well reproduced by conventional DFT functionals but does not significantly improve the results of nontransition metal oxides. Hence, we find that hybrid functionals provide a good alternative to DFT+ U for transition metal applications when the large extra computational effort is compensated by the benefits of ͑i͒ avoiding species-specific adjustable parameters and ͑ii͒ a more universal treatment of the self-interaction error that is not exclusive to specific atomic orbital projections on selected ions.

Ab initio GGA+U study of oxygen evolution and oxygen reduction electrocatalysis on the (001) surfaces of lanthanum transition metal perovskites LaBO3(B = Cr, Mn, Fe, Co and Ni)

“…These hybrid functional and GGA+U results suggest that either including the Hubbard U eff correction or using the hybrid functional method to treat correlated electron errors in DFT-GGA for transition metal oxides will make transition metal oxides less oxyphilic 19,59 , and therefore result in reduction of surface oxygen adsorption strength. This result is due to the same physics shown in studies of battery electrode Li intercalation and associated transition metal redox energies, where adding U and using hybrid methods when compared to plain DFT increases predicted Li voltages, consistent with a increase in electronegativity, which is expected to correlated with a decrease in oxyphilicity 59,60 . These trends have been associated with the correction of self-interaction terms with the DFT+U, making oxidation harder and reduction easier.…”

Enhanced magnetism of Cun clusters capped with N and endohedrally doped with Cr

“…We used a screened form of hybrid functional HSE06 proposed by Heyd, Scuseria and Ernzerhof with screening parameter 0.206. [32] Note that the hybrid HSE06 functional has been used recently to correct GGA-DFT predictions of formation energy of transition metal oxide crystals [33] as well as of magnetic interaction for transition metal clusters. [34] We find that the overall trend of enhanced magnetic moments of the N-capped Cu n clusters persists as found in the case of PBE calculations.…”

Nanostructuring of β-MnO2: The Important Role of Surface to Bulk Ion Migration

“…From our GGA+U total energy calculations for bulk β-MnO 2 we obtain a value of 3.2 V. The small difference between our GGA+U result and experiment is typical of the accuracy obtained with this method over a large class of intercalation compounds. 46 Furthermore, structural contributions to the total energy due to the mesoporous structure are not accounted for in our calculations. Nevertheless, despite the fact that bulk β-MnO 2 permits little intercalation experimentally, the accuracy of our calculated voltage indicates good reproduction of the key contributions to the thermodynamics of intercalation in mesoporous β-MnO 2 .…”