Dear Poonam Sharma,
> 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. This is strange. Are you sure that you do things properly? Can you share your input and output files for a primitive cell and a supercell? Which version of QE do you use? Please check posting guidelines: https://www.quantum-espresso.org/forum > 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. 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. HTH Iurii -- Dr. Iurii TIMROV Senior Research Scientist Theory and Simulation of Materials (THEOS) Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 ________________________________ From: users <[email protected]> on behalf of poonamsharma <[email protected]> Sent: Sunday, November 7, 2021 4:47:57 AM To: Quantum ESPRESSO users Forum Subject: [QE-users] Different band gap in unitcell and in supercell 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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