[Pw_forum] Total energy does not coverge with ecut

[Timothy Mason]

Dear Lorenzo,

here are results for the lower energy range.  Still doesn't seem to be converging.

ecut     energy              energy differnce
30        -48.19258627    
35        -48.19503183       0.00244556
40        -48.197306           0.00227417
45        -48.20217820       0.0048722

thanks

--- On Thu, 11/6/08, Lorenzo Paulatto <paulatto at sissa.it> wrote:
From: Lorenzo Paulatto <paulatto at sissa.it>
Subject: Re: [Pw_forum] Total energy does not coverge with ecut
To: thmason24 at yahoo.com, "PWSCF Forum" <pw_forum at pwscf.org>
Date: Thursday, November 6, 2008, 10:08 AM

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?

regards

-- 
Lorenzo Paulatto
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