[CP2K:9757] MGRID vs KPOINTS for small systems
sebastia... at ovgu.de
Sat Dec 2 18:06:38 UTC 2017
thank you. The way I understood it is that to get better results, I can
either increase the volume of real-space the integration happens over
(MULTIPLE_UNIT_CELLS), or can move to a model in the reciprocal lattice and
sample the 1st BZ at high(er) resolution? That means that for such a small
system, what I effectively did in my test was the same as if I used a too
coarse k-point grid? The thing that confused me was that most energies were
very similar, just that one term wildly different.
For my test system, I need 27 supercells to get the kpt energies, but even
more for correct stresses - but at about 1/10th the computation time and a
little less memory/proc that could be worth it. But now I have all
quantities output for the replicated atoms as well, making things a bit
harder to use... guess I'll stick with k-point sampling. Is there a
break-even point regarding volume or atom/electron count where one method
is generally faster than the other?
As a related question, is there a way to specify an M-P grid using point
spacing instead of point counts?
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