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CATEGORIES:Electronic Structure Discussion Group
SUMMARY:Towards automated self-correction of approximate D
FT using first-principles Hubbard U and Hund's J p
arameters - David O’Regan\, School of Physics\, CR
ANN and AMBER\, Trinity College Dublin\, The Unive
rsity of Dublin\, Dublin 2\, Ireland
DTSTART;TZID=Europe/London:20190906T141500
DTEND;TZID=Europe/London:20190906T151500
UID:TALK129277AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/129277
DESCRIPTION:In electronic structure methods based on the corre
ction of approximate density-functional theory (DF
T) for systematic inaccuracies\, Hubbard U paramet
ers may be used to quantify and amend the self-int
eraction error (SIE) ascribed to selected subspace
s. In order to enable the accurate\, computational
ly convenient calculation of U by means of DFT alg
orithms that locate the ground-state without any d
iagonalisation\, such as in linear-scaling DFT+U [
1]\, a linear-response formulation for U is introd
uced here in terms of the fully-relaxed constraine
d ground-state density [2]. Expressing the total e
nergy of self-consistent DFT+U in terms of a const
rained search over ground-state densities and exte
rnal DFT+U parameters that satisfy a self-consiste
ncy condition\, the U parameters are relegated to
the status of auxiliary variables. This enables th
e full comparability\, conceptually and numericall
y\, of approximately self-corrected DFT energies [
3\,4]\, such as when external parameters such as i
onic positions are changed.\n\nThis ground-state t
racking linear-response framework also addresses t
he open question of self-consistency over U in DFT
+U. We show that the simplest self-consistency sch
eme is necessary and sufficient for DFT+U to corre
ct the total energy for SIE under idealized one-el
ectron conditions [3]\, and that the gap can also
be simultaneously corrected if further generalisat
ions are made [4]. For multi-electron systems such
as transition-metal oxides (including closed-shel
l ones)\, we extend the framework to enable straig
htforward first-principles calculations of the Hun
d’s exchange parameter J\, which we find to be cri
tically important [5]. We also demonstrate success
ful first-principles U and J corrections for oxyge
n 2p orbitals.\n\n[1] D. D. O’Regan\, N. D. M. Hin
e\, M. C. Payne\, and A. A. Mostofi\, Phys. Rev. B
85\, 085107 (2012). \n\n[2] D. D. O’Regan and G.
Teobaldi\, Phys. Rev. B 94\, 035159 (2016). \n\n[3
] G. Moynihan\, G. Teobaldi\, and D. D. O’Regan\,
arXiv:1704.08076 (2017).\n\n[4] G. Moynihan\, G. T
eobaldi\, and D. D. O’Regan\, Phys. Rev. B 94\, 22
0104(R) (2016). \n\n[5] E. B. Linscott\, D. J. Col
e\, M. C. Payne and D. D. O’Regan\, Phys. Rev. B 9
8\, 235157 (2018).\n\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
CONTACT:Angela Harper
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