Hi all,
I seen CBM and VBM plots in articles plotted using VASP, i pasted a part of the sample picture.
I used to do with Gaussian, but can any one explain How exactly these could be plotted using VASP output?
Thank you.
To get the VBM CBM charge debsities you have to perform a PARCHG (https://www.vasp.at/wiki/index.php/PARCHG) calculation in VASP. I suggest you follow the follwing link from the ofitial VASP wiki:
https://www.vasp.at/wiki/index.php/Band-decomposed_charge_densities
where it is explained how to do those tipes of calculations.
What has worked well for me is first, do a single point calculation to see which band numbers (indices) correspond to those of the VB and CB (for exemple the 21th and 22d band). Then do another calculation with the INCAR containing:
LPARD = .TRUE. ! Toggles PARCHG calculation and processing
LSEPB = .TRUE. ! Write PARCHG for selected bands to individual files
LSEPK = .TRUE. ! Write PARCHG for selected k points to individual files
IBAND = 20 21 ! Indices of the specified bands mentioned earlier (VB CB)
And the KPOINTS file being a line from the VBM k-point to the CBM k-point (for example from (0,0,0) to (0.5, 0.5, 0)).
The calculation will return several PARCHG.IBAND.KPOINT files, and the ones you are looking for are the one containing the IBAND and KPOINT number of the VBM and CBM correspondingly. So, in my example would be PARCHG.0020.0001 (Corresponding to the VBM at (0,0,0)) and PARCHG.0021.0002 (Corresponding to the VBM at (0.5,0.5,0), the second kpoint of the line)
Diego Ontiveros Thank you for the detail reply. Good reply.
As you mentioned, "...What has worked well for me is first, do a single point calculation to see which band numbers (indices) correspond to those of the VB and CB (for exemple the 21th and 22d band)."
So, you mean to say , after i relaxed the system fully, then generally i do Band structure calculation. I think i can find the band numbers corresponding to VBM and CBM form this band structure step results?
Anyway, you suggesting as a next step do a single point calculation, NSW=0, and find for which band numbers the occupancy changes from 1 (for one band) to 0 (for the next band), to find VBM & CBM band numbers. and do the rest? So from your example will the files " ARCHG.0020.0001 (Corresponding to the VBM at (0,0,0)) and PARCHG.0021.0002" be visualised in VESTA directly. ?
SK M Yes I check the VB/CB indices by looking at the occupancy change, you can also check it by bandstructure calculation. And yes, the PARCHG files have a CHGCAR format and can be opened directly with VESTA.
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