In most cases, the ``best'' results (i.e. closest to experiment)
are obtained by iterating only G, but keeping W fixed to the initial DFT W.
This can be achieved in two manners. If the spectral method is not
selected, the QP shifts are iterated automatically four times, and you will find
four sets of QP shifts in the OUTCAR file. The first
one corresponds to the G
W
case, the final one to the GW
results.
The INCAR file is simply:
System = Si NBANDS = 96 ISMEAR = 0 ; SIGMA = 0.05 ALGO = GW0 ; NOMEGA = 50For technical reasons, it is not possible to iterate G in that manner, if LSPECTRAL=.TRUE. is set in the INCAR file. In this case, an iteration number must be supplied in the INCAR file using the NELM tag. Usually three to four iterations are sufficient for accurate QP shifts.
System = Si NBANDS = 96 ISMEAR = 0 ; SIGMA = 0.05 ALGO = GW0 ; NOMEGA = 50 NELM = 4If the spectral method is not used, the specification of NELM is not sensible. If non diagonal components of the selfenergy should be included use ALGO = scGW0.