[gpaw-users] Benzene optimization 'Did not converge'

[Marcin Dulak]

Hi,

i would start with changing mixer
https://wiki.fysik.dtu.dk/gpaw/documentation/convergence/convergence.html
Let's say:
from gpaw.mixer import Mixer
and in the calculator
mixer=Mixer(0.05, 2)
maxiter=250

As Elsebeth says, if you are interested in weakly bound systems you will 
have to verify
the convergence of the properties you are investigating with respect to 
the (very fine) grid spacing,
and to converge the forces much tighter.

Another important thing for weakly bound systems is the eggbox effect 
coming from the grid:
https://listserv.fysik.dtu.dk/pipermail/gpaw-users/2012-May/001440.html
It may be better to use the planewave mode.

Marcin

On 12/07/12 16:32, Elsebeth Schröder wrote:
>> ________________________________________
>> From: Elsebeth Schröder
>> Sent: 07 December 2012 15:27
>> To: qian li; gpaw-users at listserv.fysik.dtu.dk
>> Cc: Elsebeth Schröder
>> Subject: RE: [gpaw-users] Benzene optimization 'Did not converge'
>>
>> Hi Qian Li,
>>
>> I don't know about the KohnShamConvergeError, but once you figure that out, I suggest you lower the max force (0.01 eV/Å or lower)
>> because the energy minimum in sparse systems is shallow and the forces small. Also, and the grid spacing should be even smaller
>> than what you are testing now (I would use h=0.12 Å or > smaller). Finally, since the energy differences (like the binding energy) in
>> sparse matter systems are on the meV scale you will need to energy-converge your calculations better than the default gpaw settings.
>> For that you can use the
>> convergence={'energy':SOMENUMBER}
>> key, where SOMENUMBER is the convergence criterium in eV per electron. Thus, if your system is a benzene dimer and you want 1 meV
>> convergence on the binding energy you need to set SOMENUMBER to 10e-5.
>
> Sorry, typo, should be 1e-5
>
> /Elsebeth
>
>
>> That will likely result in a few extra electronic iterations, compared to the default.
>>
>> Best regards
>> Elsebeth
> _______________________________________________
> gpaw-users mailing list
> gpaw-users at listserv.fysik.dtu.dk
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>
>


-- 
***********************************
  
Marcin Dulak
Technical University of Denmark
Department of Physics
Building 307, Room 229
DK-2800 Kongens Lyngby
Denmark
Tel.: (+45) 4525 3157
Fax.: (+45) 4593 2399
email: Marcin.Dulak at fysik.dtu.dk

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