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Dear Experts,
I have some confusion about the selection of NBANDS, NBANDSO, and NBANDSV while performing the BSE calculations. I guess NBANDSV is doubled NBANDSO (as mentioned in the Si example on Vaspwiki: https://www.vasp.at/wiki/index.php/Diel ... _using_BSE). The selection of NBANDS is not clear to me. Can you please suggest the selection of NBANDS in the system. Is this depeds on the no. of atoms in the system.

Hi,

In the BSE calculations, NBANDS should be set to the same value as in the preceding GW step, so that VASP can read the WAVECAR and WAVEDER files. The bands included in the BSE equation are set by NBANDSO and NBANDSV and should be found through convergence tests. If NBANDSV and NBANDSO are not set, VASP includes all the occupied orbitals and an equal number of empty orbitals.
You can also find more details in the wiki guide.