[Pw_forum] Total energy does not coverge with ecut

Lorenzo Paulatto paulatto at sissa.it
Thu Nov 6 17:08:40 CET 2008

Timothy Mason ha scritto:
>     Gentlemen,
> My structures do not see to be converging with increased ecutwfc.  
> I'm setting ecutrho to ecutwfc * 12 and using US PP.    below is a
> table of ecut values vs energies vs difference from previous steps
> followed by my input file followed by part of the output file.    It
> appears to begin to converge and 120 ecut but then jumps at 130 and
> then more at 140.
Dear Timothy,
these are ridiculous cutoff energy for ultrasoft pseudopotentials - they
are very high for norm-conserving too! I suspect the presence of a
high-energy ghost-state in one of the pseudopotential; these kind of
states aren't usually harmful but can suddenly pop-up under some
specifics conditions like high pressure or very high cutoff.

What is happening when you try some reasonable cutoff in the 20-50 Ry range?


Lorenzo Paulatto
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