Rotationally invariant ab initio evaluation of Coulomb and exchange parameters for DFT + U calculations
Conventional density functional theory (DFT) fails for strongly correlated electron systems due to large intra-atomic self-interaction errors. The DFT + U method provides a means of overcoming these errors through the use of a parametrized potential that employs an exact treatment of quantum mechani...
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Veröffentlicht in: | The Journal of chemical physics 2008-07, Vol.129 (1), p.014103-014103-13 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Conventional density functional theory (DFT) fails for strongly correlated electron systems due to large intra-atomic self-interaction errors. The
DFT
+
U
method provides a means of overcoming these errors through the use of a parametrized potential that employs an exact treatment of quantum mechanical exchange interactions. The parameters that enter into this potential correspond to the spherically averaged intra-atomic Coulomb
(
U
)
and exchange
(
J
)
interactions. Recently, we developed an
ab initio
approach for evaluating these parameters on the basis of unrestricted Hartree-Fock (UHF) theory, which has the advantage of being free of self-interaction errors and does not require experimental input [
Mosey
and
Carter
,
Phys. Rev. B
76
,
155123
(
2007
)
]. In this work, we build on that method to develop a more robust and convenient
ab initio
approach for evaluating
U
and
J
. The new technique employs a relationship between
U
and
J
and the Coulomb and exchange integrals evaluated using the entire set of UHF molecular orbitals (MOs) for the system. Employing the entire set of UHF MOs renders the method rotationally invariant and eliminates the difficulty in selecting unambiguously the MOs that correspond to localized states. These aspects overcome two significant deficiencies of our earlier method. The new technique is used to evaluate
U
and
J
for
Cr
2
O
3
, FeO, and
Fe
2
O
3
. The resulting values of
U
-
J
are close to empirical estimates of this quantity for each of these materials and are also similar to results of constrained DFT calculations.
DFT
+
U
calculations using the
ab initio
parameters yield results that are in good agreement with experiment. As such, this method offers a means of performing accurate and fully predictive
DFT
+
U
calculations of strongly correlated electron materials. |
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ISSN: | 0021-9606 1089-7690 |
DOI: | 10.1063/1.2943142 |