The ABINIT Users Mailing List ( CLOSED )

["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi Joe and Marc

From your post it looks like this is happening with PAW pseudo ?
Have you tested if  the same thing happens with norm conserving ones ?
If no could you provide a sample input we can play with ?

regards

PMA


On Mon, Oct 13, 2008 at 3:51 PM, Josef W. Zwanziger
<jzwanzig@jzwanzig.org> wrote:
> Thanks Marc and PMA for your comments. Here's the situation so far (I'm not
> sure I've done exactly the tests you wanted, but maybe I have...)
>
> 1) I optimized Si with optcell 1, ionmov 2, tolmxf 1.0D-6, tolvrs 1.0D-10 in
> three ways:
> ecutsm1 0.5, dilatmx1 1.1
> ecutsm2 1.0, dilatmx 1.1
> ecutsm3 0.5, dilatmx 1.5
>
> All optimize to the same acell within about a part in 10^6, and stress about
> 10^{-4} GPa
>
> 2) Re-run all three optimized acell's as SCF calc's (optcell = 0, ionmov =
> 0) but with ecutsm and dilatmx as in 1). Final stress about the same as 1),
> that is, 10^{-4} GPa or less.
>
> 3) Re-run all three acell's as SCF calc's, with ecutsm and dilatmx at
> defaults (0 and 1), then final stress about 10^{-2} GPa.
>
> 4) Re-run like in 2, but with dilatmx set to run 1 values, ecutsm left at 0,
> final stress also about 10^{-2} GPa.
>
> 5) Re-run like in 2, but with ecutsm set to run 1 values, dilatmx left at
> default of 1: final stress about 10^{-3} GPa
>
> 6) Finally, in order to check whether this is the effect of "Pulay stress"
> as suggested by one of my colleagues here, I re-ran runs 1-3 above with ecut
> = 30 instead of 15, and pawecutdg = 60 instead of 30, but I got about the
> same results as above.
>
> what are your thoughts?
>
> Joe
>
> Josef W. Zwanziger
> Professor of Chemistry
> Canada Research Chair in NMR Studies of Materials
> Director, Atlantic Region Magnetic Resonance Centre
> Department of Chemistry
> Dalhousie University
> 6274 Coburg Road
> Halifax, Nova Scotia B3H 4J3 Canada
> tel: +1.902.494.1960
> fax: +1.902.494.1310
> web: http://jwz.chem.dal.ca
> jzwanzig@jzwanzig.org,jzwanzig@dal.ca
>
> ----- Original Message ----
> From: TORRENT Marc <marc.torrent@cea.fr>
> To: forum@abinit.org
> Sent: Monday, October 13, 2008 6:36:38 AM
> Subject: Re: [abinit-forum] Questions about optcell /= 0 and ecutsm
>
> Hi PMA and Joe,
>
> Additional comment:
>
> * ecutsm directly influence the way some plane waves are taken into account;
> so it has to be the same in both runs.
> * dilatmx does not : it is only used to dimensioned arrays (in order to take
> into account future increasing of number of PW). And additional components
> are filled withs zeros.
>
> In others words, internal variables are:
> - ecut used to select plane-waves
> - ecuteff=ecut*dilatmx**2 used to dimensioned arrays
> Array components due to use of dilatmx and not included by ecut are filled
> with zeros.
>
> But this is theory !; if a bug is there...
>
> So Joe, aditional questions:
> - is the total (converged) energy the same in both runs
> - same question for forces...
>
> If yes (for both questions) the problem probably occurs in 'forstrnps'
> routine where dilatmx might not be correctly taken into accound; but, this
> is speculation...
>
> You also can test (as PMA asked) with and with the same dilatmx in the
> second run. It will give a good clue.
> But the test proposed by PMA is not correct (sorry Pierre-Matthieu); using
> ecut*dilatmx**2 will necessarily give different results.
>
> Marc
>
>
>
> Anglade Pierre-Matthieu a écrit :
>
> Hi,
>
> You mentioned keeping ecutsm constant between the two runs but what
> about dilatmx ?
> Did you tried the second run with a ecut2=ecut1*dilatmx**2 ?
>
> regards
>
> PMA
>
> On Sat, Oct 11, 2008 at 5:56 PM, Josef Zwanziger <jzwanzig@dal.ca> wrote:
>
>
> Dear Colleagues,
> I've noticed this behavior in the past and never really understood it. I
> would
> really appreciate an explanation from someone.
>
> When I optimize a cell with optcell = 1 or 2, and dilatmx = 1.1 and ecutsm
> /= 0
> as required, I find typically that the cell optimizes nicely and the final
> computed pressure is very small, of course determined by whatever value I
> set
> tolmxf to. Then, if I cut and paste the new acell and xred and rprim, and do
> a
> normal ground state SCF run with the same convergence level (using either
> toldff or tolvrs), the computed final pressure is usually several orders of
> magnitude larger than the final value achieved in the optimization run. For
> example, if I choose really easy case like Si, I can optimize it to a
> computed
> final pressure of 1E-4 GPa, and then those cell parameters in an SCF
> calculation will give a pressure of 1E-2. This gets worse in big cells,
> where I
> might
>  optimize to 1E-2 and then the SCF run gives 1 GPa. Why does this happen?
> It seems to be independent of the value of ecutsm, and also I am running at
> a
> pretty dense kpt set (kptrlen = 80). Any comments?
>
> thanks,
> Joe Zwanziger
>
>
>
>
>



-- 
Pierre-Matthieu Anglade