TURBOMOLE Users Forum
TURBOMOLE Modules => Escf and Egrad => Topic started by: martijn on April 21, 2021, 11:11:30 AM

Hi,
I have observed that qsGW needs typically many more (10+) iterations than qsGW (34) in order to converge. Is that to be expected?
Thanks,
Martijn

Hi,
indeed this is to be expected; qsGW will in general need many more iterations than evGW and sometimes even more than HF/DFT calculations. qsGW updates all the FockMatrix elements, making a rediagonalization of the FockMatrix necessary in every iteration. Especially in cases were the selfenergy has peaks close to the FockMatrix elements a steep dependence of the latter to small changes can be expected. This leads to a rather slow convergence, and DIIS is not helping too much in these cases. In evGW only the eigenvalues/quasiparticle energies but not the eigenvectors of the FockMatrix are updated, a rediagonalization is not needed. Therefore, it converges pretty fast especially with DIIS.
All the best,
CHristof

Thanks Christof