let me be a bit "destructive" here, but just to stimulate (excite?) convincing arguments against mine… How "useful" is the GWA approximation, in electronic structure calculations? I perfectly understand the importance of the underlying theoretical background, in particular to recover some meaning to DFT DOS calculations with respect to experimental spectra, but from a practical standpoint… I followed the tutorial and applied it to a simple 3C-SiC simulation and what I've noticed is that the result on the band structure curves is "only" an almost linear stretching of the energy scale, about 10%. See for example this plot:
That should also be demostrable, to some extent, I think… I miss the literature here. As explained in the tutorial, careful choice of computational parameters is required to properly fit the GW results with experimental values (typically the gap energy). This is not a true ab-initio, in my understanding, against an increased cost of tenfold, or more, computational resources. Why then not using just the energy "stretching" as the fitting parameter and forget the GW at all? Any practical use case where GW is unavoidable (in calculations, I mean)?
Thanks all for the great job!