[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
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/

Due to budget cuts approved by Italian Minister of Finance and Italian
Minister "for" Education, University and Research this may be the
last
email you receive from me.

Please send any future correspondence, possibly via pigeon, to
mr. Lorenzo Paulatto
under Roiano Railway Bridge - Pillar 2
34136, Trieste

Donations in food, coins, booze and processor time are warmly welcome.



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.democritos.it/pipermail/pw_forum/attachments/20081106/6ace72d9/attachment.htm