Hi Vishwajeet,

1) I had checked your DOS plot from the attached document. According to me your dos plot is correct and it is in agreement to the previously reported dos plots.

2) Speaking about the band gap, band gap is the gap between valence band maximum (VBM) and the conduction band minimum (CBM) in the dos as well as in the band structure. It is very clear from your dos plot that the gap between -6 to 0 is your band gap. This is in accordance with the Fig 8. of the following reference.

https://link.springer.com/content/pdf/10.1134/S106378341402022X.pdf

I agree with the above answer, the band gap can be found out simply looking at the gap between valence band maximum (VBM) and the conduction band minimum (CBM). Just see where is the Fermi level and from there you can get the idea about valence band and conduction band.

I am trying to do scf calculations on qe but i found this error

@echo off

echo ******************************

echo ** Quantum ESPRESSO end **

echo ******************************

echo Exit in 10 seconds.

ping -n 10 localhost > nul

Please let know how to override this problem

Dear Kiran Kumar,

Please check the subroutine in QE directory for the overlap of atoms by

find ./ -name \*.f90 -print | xargs grep overlap | grep atoms

Also check your atomic coordinates and alat whether it is in angstroms or not and also check the periodic box size.

@ Sai Phani Kumar Vangala how we find the exact value of band gap? also can we find the exact value of valence band maximum (VBM) and conduction band minimum (CBM).

@Sajid Ur Rehman

Dear Sajid,

If you perform DFT calculations from the suitable computational chemistry platform, you will get optimized structures from which you can run 'dos' calculations to generate total density of states and partial density of states from which you can measure band gap of a given molecule.

Suppose if you use Generalized Gradient Approximation (GGA) to find the band gap from the computations, it underestimates the band gap of most of the metal oxides. So in order to calculate the accurate band gap which should be an approximate to the experimental reported one, you should use GGA+U or Hybrid functionals for ex. PBE0, HSE, HSE06 etc. during structural optimizations.

Else, you can also generate the band structures from which you can clearly differentiate the valence band maximum (VBM) and conduction band minimum (CBM) and the Fermi level. Normally, Fermi level would be set at zero. The states appears on the bottom of Fermi level were bands of the valence states and the states which lies above the Fermi level corresponds to the conduction band states. The gap between the CBM and the Fermi level is the band gap.

How to get the correct valence bandwidth (or the bottom energy of the valence band) from the DOS plot?