# Calculating band gap in CP2K

Hi,

I am trying to calculate band gap in CP2K for an electrolyte.

On the internet, I found two ways to find the band gap.

i) Look into one of the .pdos files generated by CP2K and find the energies where the occupation number changes from 2 to 0. Subtract the two energies and convert the result from Hartree to eV.

For example, in the .pdos file I have the following values of energies where the occupation number of the s orbital changes from 2 to 0.

# Projected DOS for atomic kind F5 at iteration step i = 0, E(Fermi) =    -0.047273 a.u.
#     MO Eigenvalue [a.u.]      Occupation                 s                 p                 d
………..

………..

623         -0.047273        2.000000        0.00025286        0.00408688        0.00012177
624          0.133668        0.000000        0.00642493        0.02456380        0.00249863

………

So band gap =
0.133668+
0.047273 =
0.180941 Ha

ii) Use Tiziano’s script for each of the .pdos files, add the pdos values of all the element types (keeping the corresponding energy value same) to get TDOS.

Plot E vs TDOS, and look for the band where TDOS stays at zero.

I am not sure which method to choose to get band gap and I am getting slightly different answers from the two methods. Also, in case of TDOS, how to choose the tolerance below which I can say that the TDOS is zero, to define the band gap? Currently I am using the criterion that all values less than 0.05 % of the maximum will be considered as zero.

Thanks,

Ramanish