Publication Date:
2016-04-13
Description:
Density-functional theory plus the Hubbard U correction (DFT + U ) method is widely used in first-principles studies of strongly correlated systems, as it can give qualitatively (and sometimes, semi-quantitatively) correct description of energetic and structural properties of many strongly correlated systems with similar computational cost as local density approximation or generalized gradient approximation. On the other hand, the DFT + U approach is limited both theoretically and practically in several important aspects. In particular, the results of DFT + U often depend on the choice of local orbitals (the local projection) defining the subspace in which the Hubbard U correction is applied. In this work we have systematically investigated the issue of the local projection by considering typical transition metal oxides, β -MnO 2 and MnO, and comparing the results obtained from different implementations of DFT + U . We found that the choice of the local projection has significant effects on the DFT + U results, which are more significant for systems with stronger covalent bonding (e.g., MnO 2 ) than those with more ionic bonding (e.g., MnO). These findings can help to clarify some confusion arising from the practical use of DFT + U and may also provide insights for the development of new first-principles approaches beyond DFT + U .
Print ISSN:
0021-9606
Electronic ISSN:
1089-7690
Topics:
Chemistry and Pharmacology
,
Physics
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