Dear Experts, Thank you so much for your quick response and useful information. I am going to try these suggestions. I'll update here if I'll get the correct results. Thanks once again.
Thanks and regards, Poonam S. ------------------------------------------------------------------------------------------------- Poonam Sharma Research Scholar Department of Physics Indian Institute of Technology Bombay Mumbai - 400076 India. On Thu, Nov 11, 2021 at 1:08 PM poonamsharma <[email protected]> wrote: > 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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