Dear Sir, >The band gap should not change: in a supercell you will have more electronic >bands but the band gap must remain the same. Again, please check that you do >all properly or share your files.
Thank you so much fr this suggestion. I guess I am taking wrong K points. Also I didn't perform the K points convergence test for supercell. This may be one the reson of this discrepancy. I'll chk this again, also I am thinking to perform convergence test for each supercell. Only one query I have, my a,b,c parameters for unitcell are 13.764, 3.699, 3.95. It is bulk system. For K points convergence wrt energy, I took K points sets like 2x2x2 3x3x3... like this , and at 5x5x5 I obtained a good convergence. Since my a,b,c are not equal so I am taking in SCF calculation 5X10X9. This 5X10X9 set is correct to to take although at 5X5X5 I obtained the convergence. Thank you so much once again. Thanks and regards, Poonam Sharma ------------------------------------------------------------------------------------------------- Poonam Sharma Research Scholar Department of Physics Indian Institute of Technology Bombay Mumbai - 400076 India. On Sun, Nov 7, 2021 at 9:17 AM poonamsharma <[email protected]> wrote: > Dear users, > I am trying to calculate the bandgap for one system in the unit cell and > in the supercell of 2x2x1 and 3x1x1. Although 3x1x1 gives the same bandgap > as I got from the unit cell (1.80 eV) but 2x2x1 is giving 1.75 eV. I kept > the input files settings same in supercells as in-unit cell including K- > POINTS. I observed this bandgap by plotting the dos. I think the bandgap > should remain the same in the supercell. > Is this 1.75 eV is acceptable. > Also in order to match this bandgap with the experimental value, I applied > the U parameter. In unit-cell with different U values, I got a variation in > band gap that I am expecting but in supercell, bandgap remains the same, no > variation observed. > I'll be very thankful for any suggestions. > > Thanks and regards, > Poonam Sharma > > > > > ------------------------------------------------------------------------------------------------- > Poonam Sharma > Research Scholar > Department of Physics > Indian Institute of Technology Bombay > Mumbai - 400076 > India. > >
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