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BEGIN:VEVENT
DTSTAMP:20240519T232009Z
UID:https://www.mpsd.mpg.de/events/9631/2724
DTSTART:20170425T111500Z
DTEND:20170425T121500Z
CLASS:PUBLIC
CREATED:20170412T143717Z
DESCRIPTION: The electronic and optical properties of a material critically
depend on its defects\, and understanding that requires substantial and a
ccurate input from theory. Defect calculations in traditional semiconducto
rs have relied on the local and semi/local approximations of density funct
ional theory\, which in wide band gap materials may lead to fatal errors.
Since first-principle total energy methods beyond these approximations can
not yet be carried out with sufficient accuracy for the supercells needed
in defect calculations\, nowadays semi-empirical hybrid functionals are of
ten applied instead. In my talk I will analyze the performance of the HSE0
6 screened hybrid functional on defects in Group-IV semiconductors and in
TiO_{2}\, and show that its success is the result of error compens
ation between semi-local and non-local exchange\, resulting in a proper de
rivative discontinuity (reproduction of the band gap) and a total energy w
hich is a linear function of the fractional occupation numbers (removing m
ost of the electron self-interaction). As it is well known\, however\, HSE
06 does not work equally well for all materials. On the example of Ga_{
2}O_{3}\, I will show that tuning both the mixing and the scr
eening parameter of HSE for the given material allows to ensure the same e
rror compensation. Unless the electronic screening is strongly direction-
or orbital-dependent (as in ZnO)\, the optimized HSE hybrid is nearly self
-interaction free and provides a band structure on par with GW. Since the
total energy can also be calculated\, the real equilibrium structure of a
defect can be found and the levels are in good agreement with experimental
observations.\nVortragende(r): Peter Deák
LAST-MODIFIED:20170412T143717Z
LOCATION:CFEL (Bldg. 99)\, Raum: Seminar Room IV\, O1.111
ORGANIZER;CN=Angel Rubio:mailto:
SUMMARY:MPSD Seminar: Peter Deák - How to choose the correct hybrid funct
ional for defect calculations
URL:https://www.mpsd.mpg.de/events/9631/2724
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