[Pw_forum] What is the exact criteria for scf convergence?
Emine Kucukbenli
kucukben at gmail.com
Sat Feb 7 15:45:41 CET 2015
Hi M, The parameter in play here is called "upscale", take a look at the
description of it in input parameters list. (Also for big systems one might
want to keep in mind that conv_thr is an extensive quantity) cheers - emine
On Sat, Feb 7, 2015 at 3:11 PM, MKondrin <mkondrin at hppi.troitsk.ru> wrote:
> Hello!
>
> I try to optimize quite large structure (several tens of atoms in the
> unit cell) but I can not quite get that is the criteria of convergence
> to proceed for the next optimization cycle. I use QE 5.01
>
> I have in the preamble of input file something like:
>
> &control
> calculation='relax',
> prefix='scf',
> tstress=.true.,
> tprnfor=.true.,
> pseudo_dir = '../pseudo',
> outdir='./tmp'
> /
> &system
> ibrav=0,
> celldm(1) = 12.60447,
> ntyp=2,
> nat=84,
> ecutwfc=70,
> ecutrho=800,
> occupations='fixed'
> /
> &electrons
> mixing_beta = 0.7,
> conv_thr = 1.0d-6
> /
> &ions
> /
> ....
>
> I suppose that the next cycle of structure optimization should occur
> than the accuracy of self consistent calculations of about 1e-6 Ry.
>
> However in the output file I get this (this is the end of one scf cycle)
>
> iteration # 20 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 5.68E-10, avg # of iterations = 1.0
>
> total cpu time spent up to now is 230665.4 secs
>
> total energy = -823.97008715 Ry
> Harris-Foulkes estimate = -823.97008883 Ry
> estimated scf accuracy < 0.00000279 Ry
>
> iteration # 21 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 5.68E-10, avg # of iterations = 4.0
>
> total cpu time spent up to now is 233303.9 secs
>
> total energy = -823.97008869 Ry
> Harris-Foulkes estimate = -823.97008855 Ry
> estimated scf accuracy < 0.00000071 Ry
>
> iteration # 22 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 3.37E-10, avg # of iterations = 1.0
>
> total cpu time spent up to now is 236012.3 secs
>
> total energy = -823.97008898 Ry
> Harris-Foulkes estimate = -823.97008869 Ry
> estimated scf accuracy < 0.00000092 Ry
>
> iteration # 23 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 3.37E-10, avg # of iterations = 3.5
>
> total cpu time spent up to now is 238645.5 secs
>
> total energy = -823.97008880 Ry
> Harris-Foulkes estimate = -823.97008904 Ry
> estimated scf accuracy < 0.00000178 Ry
>
> iteration # 24 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 3.37E-10, avg # of iterations = 1.0
>
> total cpu time spent up to now is 241385.7 secs
>
> total energy = -823.97008829 Ry
> Harris-Foulkes estimate = -823.97008881 Ry
> estimated scf accuracy < 0.00000147 Ry
>
> iteration # 25 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 3.37E-10, avg # of iterations = 3.9
>
> total cpu time spent up to now is 244038.6 secs
>
> total energy = -823.97008797 Ry
> Harris-Foulkes estimate = -823.97008835 Ry
> estimated scf accuracy < 0.00000057 Ry
>
> iteration # 26 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 2.72E-10, avg # of iterations = 4.0
>
> total cpu time spent up to now is 246730.6 secs
>
> total energy = -823.97008832 Ry
> Harris-Foulkes estimate = -823.97008847 Ry
> estimated scf accuracy < 0.00000043 Ry
>
> iteration # 27 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 2.03E-10, avg # of iterations = 1.0
>
> total cpu time spent up to now is 249273.6 secs
>
> total energy = -823.97008831 Ry
> Harris-Foulkes estimate = -823.97008833 Ry
> estimated scf accuracy < 0.00000021 Ry
>
> iteration # 28 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 9.87E-11, avg # of iterations = 1.1
>
> total cpu time spent up to now is 252028.1 secs
>
> total energy = -823.97008826 Ry
> Harris-Foulkes estimate = -823.97008832 Ry
> estimated scf accuracy < 0.00000017 Ry
>
> iteration # 29 ecut= 70.00 Ry beta=0.70
> Davidson diagonalization with overlap
> ethr = 8.33E-11, avg # of iterations = 6.2
>
> total cpu time spent up to now is 254596.4 secs
>
> End of self-consistent calculation
>
>
> Aren't the cycles after #25 superfluous, because energy difference
> between two successive steps and estimated accuracy is less than 1e-6
> Ry? What is the control parameter that help me to reduce the number of
> steps ?
>
> Thank you in advance!
>
> M. V. Kondrin (High Pressure Physics Institute RAS, Troitsk, Russia)
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20150207/0e2e2ce3/attachment.html>
More information about the users
mailing list