[QE-users] How i can get correct band gap by GGA+U method ?

[mohammed lamhani]

hello QE users,

I have calculated the cell parameters and band-gap energy by GGA and GGA+U
for CaMnO3 materiels (orthorhombic structure ). I tried two U values, one
from the literature (U1=4.18 eV) and I have calculated the other one by the
first principal method with the quantum espresso package (U2=5.7722 eV ).
The band-gap energies whose I have calculated by GGA, GGA+U1 and GGA+U2 are
0.71eV, 0.80 eV and 0.88 eV respectively. However, these values are very
small in comparison to the experimental result Eg=3.07 eV.

U2  was calculated by hp.x code in QE (version 6.5) package with 2*1*2 and
2*2*2 kpoints. In addition,  2*1*2 and 2*2*2 gave the same U2 value .

you can find my input files below

--
*Best regards,*
-------------------------------------
*Mohammed Lamhani,* Ph.D.
*LS3M Laboratory, Polydisciplinary Faculty of Khouribga, Sultan Moulay
Slimane University of Beni Mellal, Morocco.*
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