[Pw_forum] Re: Pw_forum digest, Vol 1 #1029 - 5 msgs

[Nicola Marzari]

aarti srirangarajan wrote:
> 
> Thanks for the reply.
> The degauss value I am working with is 0.003. What value should typically
> be used for Ni?
> regards
> aarti


Such small value will require a large amount of kpoints to
converge forces and energies. My rule of thumb is between 0.1 eV
and 0.5 eV (REMEMBER TO divide by 13.5068 to obtain the correct degauss
for pwscf).

0.1eV is really small, to be used for difficult/magnetic cases. 0.5eV
is large, for simple metals like Al.

The larger the smearing, the fewer kpoints needed for an accurate
integration (functions are smoother). But, the larger the smearing,
the further away you move from the zero-temperature target.

So it's a tradeoff, and you need to find the sweet spot.

You should use either methfessel-paxton or marzari-vanderbilt, as a
smearing scheme. I prefer the latter.


				nicola



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Prof Nicola Marzari   Department of Materials Science and Engineering
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