[Wien] runtime for lapw2 -qtl -p

[Ludwig, Christian]

My supercell is only 2x2x2, the complicated unit cells makes for 128 atoms total. So as I understand it, my 108 k-point are effectively worth 864 k-points, which is not terribly much. And I am dealing with a semiconductor, no idea how that influences a reasonable number of k-points.

Thanks for your comments.
Cheers,
Christian
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Peter Blaha [pblaha at theochem.tuwien.ac.at]
Gesendet: Donnerstag, 18. Dezember 2008 11:17
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] runtime for lapw2 -qtl -p

Yes, x lapw2 -qtl -p runs actually on only one processor. It also does a lot of
I/O, thus it is for bigger cases quite slow (but you do it only once and it blocks
only one processor).

On the other hand: why are you using for a 128 atom supercell 108 k-points ?

If you do fcc Cu a "poor" k-mesh is 10x10x10, a good one 20x20x20.
A 5x5x5 supercell of Cu (125 atoms/cell) would thus need a 2x2x2 (or 4x4x4)
mesh, which even without symmetry (but plus inversion) would lead to only
"a few" k-points in the BZ.

If you have an insulator, this k-mesh can be reduced by another order of magnitude.

Use a mesh which is in a reasonable range and optimally compatible with your 16
processors.


Ludwig, Christian schrieb:
> Hello,
>
> I am calculating a 128 atom supercell with a random distribution of a constituent, so no symmetry operations. The SCF converged in 75 hours (22 iterations, 108 k-points, 16 procs) and now I am running lapw2 -qtl -p to get the DOS. Since this is not parallel it takes an awful lot of time. Over 50 hours and still running. Now I cannot help but wonder: Is it normal, that this part takes as long as the total SCF convergence or is there something wrong?
>
> Kind regards,
> Christian
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

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                                       P.Blaha
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