[Pw_forum] Error in routine sym_rho_init_shell "lone, vector" with fixed FFT dimension

[Thomas Gruber]

On 02/08/2014 12:00 PM, pw_forum-request at pwscf.org wrote:
> Message: 2 Date: Fri, 07 Feb 2014 16:25:14 +0100 From: Paolo Giannozzi 
> <paolo.giannozzi at uniud.it> Subject: Re: [Pw_forum] Error in routine 
> sym_rho_init_shell "lone vector" with fixed FFT dimension To: PWSCF 
> Forum <pw_forum at pwscf.org> Message-ID: 
> <1391786714.5521.99.camel at fe12lx.fisica.uniud.it> Content-Type: 
> text/plain; charset="UTF-8" On Thu, 2014-02-06 at 12:58 +0100, Thomas 
> Gruber wrote:
>> >  I attached 2 inputs files. One with smaller volume works and one with
>> >  greater volume with the corresponding *.out file, which works not. Since
>> >  I have already done phonon calculations for 5 different volumes, I don't
>> >  want to change the FFT dimension. I fixed it to 48 48 200 and the not
>> >  fixed FFT dimension would be 50 50 200.
>> >  Any suggestions?
> it works if you reduce by a little bit "ecutrho" from its default value
> 4*ecutwfc. The problem is that if you keep the FFT grid fixed, you may
> "miss" a few G-vectors. The algorithm that divides G-vectors into shells
> of vectors transforming into each other cannot work if a shell is
> incomplete. Alternatively: remove symmetry, since such algorithm is
> used only for symmetrization of the charge density. I have no better
> ideas right now: finding an algorithm that is guaranteed to work if
> the FFT grid is not sufficient to accommodate the G-vector sphere
> up to G^2<  ecutrho may require a serious effort
>
> Paolo
>
Thanks, that works. If I change the "ecutrho" value than I don't have to 
fix the FFT dimension. I fixed the FFT dimension to keep the energies 
for all volumes for a QHA calculation comparable and to not get energy 
jumps. Would that work if I just reduce the ecutrho in that amount to 
keep the G-vectors constant? For my case I would have to decrease the 
"ecutrho" from 320 to 290 by 5% volume increase.

Best regards,
Thomas Gruber

-- 
TU Bergakademie Freiberg

Dipl. Chem. Thomas Gruber
Institut für Theoretische Physik
Leipziger Str. 23 / OG. 14
D-09599 Freiberg

Tel: +49 3731 39-2006
Email:thomas.gruber at physik.tu-freiberg.de
Webseite: tu-freiberg.de

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