The ABINIT Users Mailing List ( CLOSED )

["Pietro Delugas" <delugas@dsf.unica.it>]

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
> <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
>