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["Josef W. Zwanziger" <jzwanzig@jzwanzig.org>]

Hi,
the tests I posted were for Si, for which you can't use toldff because the 
forces vanish at the Si sites by symmetry.However, I have seen this happen in 
other less symmetric cases as well.

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: Pietro Delugas <delugas@dsf.unica.it>
> To: forum@abinit.org
> Sent: Thursday, October 16, 2008 5:32:38 AM
> Subject: Re: [abinit-forum] Questions about optcell /= 0 and ecutsm
> 
> have you tried  using  toldff as convergence parameter, in place of tolvrs ?
> 
> 
> > 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
> > 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 
> >> 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 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
> >