[QE-users] Total force does not coverge

Thomas Brumme thomas.brumme at uni-leipzig.de
Wed Mar 6 12:25:56 CET 2019


Dear Gui,

in addition to the point mentioned by Lorenzo, I wonder if your c-axis 
is large enough...
Let's say you calculate the Fe(110) surface by 3 layers, which is a good 
starting point but
might be not enough, your system has a thickness of about 10 Angstrom - 
2 times the
lattice spacing of Fe(110) plus the spacing iron-graphene plus the 
graphene-oxygen distance.
This leaves 15 Angstrom or less for the distance between the repeated 
slabs. This seems
rather small to me even if it might be enough. Additionally, you could 
have a dipole in your
system due to charge transfer and thus you should add the dipole 
correction. Especially,
the dipole could play an important role in the correct adsorption energy 
and geometry
and thus also for the convergence of forces.

Regards

Thomas

On 3/6/19 10:02 AM, Gui Wei wrote:
> Dear QE users,
> I am trying to optimize the adsorption system that contain Fe(110) 
> substrate and single-layer graphene connected to an oxygen atom.I got 
> the total force and the energy like this.At first, everything was 
> fine,but after 0.006846 the total force began to increase ,causing the 
> total force not to converge ,it is a extremely strange result.Is there 
> any way to solve this problem?
>
> Any suggestions would be greatly appreciated.
> Thank you.
>
>
> Total force =     0.316790       energy   new   = -4107.2627566975 Ry
> Total force =     0.246608       energy   new   = -4107.3151393348 Ry
> Total force =     0.156503       energy   new   = -4107.3635865834 Ry
> Total force =     0.119628       energy   new   = -4107.3895957292 Ry
> Total force =     0.078444       energy   new   = -4107.3969303863 Ry
> Total force =     0.052366       energy   new   = -4107.4017754787 Ry
> Total force =     0.040309       energy   new   = -4107.4042249914 Ry
> Total force =     0.033754       energy   new   = -4107.4058726129 Ry
> Total force =     0.028026       energy   new   = -4107.4071437156 Ry
> Total force =     0.025319       energy   new   = -4107.4081667548 Ry
> Total force =     0.024093       energy   new   = -4107.4089392392 Ry
> Total force =     0.022277       energy   new   = -4107.4096467799 Ry
> Total force =     0.019561       energy   new   = -4107.4102126980 Ry
> Total force =     0.016523       energy   new   = -4107.4106348116 Ry
> Total force =     0.014292       energy   new   = -4107.4109663982 Ry
> Total force =     0.013121       energy   new   = -4107.4112149183 Ry
> Total force =     0.011934       energy   new   = -4107.4114021825 Ry
> Total force =     0.011261       energy   new   = -4107.4115692713 Ry
> Total force =     0.010521       energy   new   = -4107.4117253881 Ry
> Total force =     0.009179       energy   new   = -4107.4118535327 Ry
> Total force =     0.008233       energy   new   = -4107.4119532022 Ry
> Total force =     0.007949       energy   new   = -4107.4120378076 Ry
> Total force =     0.007614       energy   new   = -4107.4121212783 Ry
> Total force =     0.007100       energy   new   = -4107.4121953505 Ry
> Total force =     0.006846       energy   new   = -4107.4122538477 Ry
> Total force =     0.006967       energy   new   = -4107.4123143593 Ry
> Total force =     0.007559       energy   new   = -4107.4123893617 Ry
> Total force =     0.007912       energy   new   = -4107.4124672492 Ry
> Total force =     0.007587       energy   new   = -4107.4125386594 Ry
> Total force =     0.007532       energy   new   = -4107.4126143150 Ry
> Total force =     0.008046       energy   new   = -4107.4126949028 Ry
> Total force =     0.008145       energy   new   = -4107.4127766088 Ry
> Total force =     0.008142       energy   new   = -4107.4128651944 Ry
> Total force =     0.009356       energy   new   = -4107.4129774552 Ry
> Total force =     0.011161       energy   new   = -4107.4131286975 Ry
> Total force =     0.012473       energy   new   = -4107.4133389405 Ry
> Total force =     0.013542       energy   new   = -4107.4136064842 Ry
> Total force =     0.014769       energy   new   = -4107.4138982197 Ry
> Total force =     0.015571       energy   new   = -4107.4142168735 Ry
> Total force =     0.015344       energy   new   = -4107.4145642683 Ry
> Total force =     0.015134       energy   new   = -4107.4149145704 Ry
> Total force =     0.016511       energy   new   = -4107.4152819587 Ry
> Total force =     0.016788       energy   new   = -4107.4156041418 Ry
>
>
>  &control
>     calculation  = 'relax',
>     prefix='epoxy1',
>     restart_mode='from_scratch'
>     pseudo_dir = '/public/home/duan1/GuiWei/pseudo/',
>     outdir='/public/home/duan1/GuiWei/tempdir/'
>     tstress = .true.
>     tprnfor = .true.
>     etot_conv_thr=1.0D-4
>     forc_conv_thr=1.0D-3
> /
>  &system
>     ibrav= 0,
>     nat=125,
>     ntyp=3,
>     nspin = 2
>     starting_magnetization(1) =0.4
>     occupations='smearing',
>     smearing='mp',
>     degauss=0.02,
>     ecutwfc =37.0
>     ecutrho =300.0
>     vdw_corr='DFT-D'
>     london_s6 = 0.75
> /
> &electrons
>     conv_thr =  1.0d-8
>     mixing_beta = 0.2
>     mixing_mode = 'local-TF'
>     mixing_ndim=16
>     electron_maxstep=200
> /
> &IONS
>   ion_dynamics='bfgs'
> /
> CELL_PARAMETERS angstrom
> 19.68000000000000       0.000000000000011  0.000000000000000
> 0.000000000000000       8.521689973238880  0.000000000000000
> 0.000000000000000       0.000000000000000  25.00000000000000
> ATOMIC_SPECIES
> Fe  55.847   Fe.pbe-nd-rrkjus.UPF
> C  12.0107   C.pbe-rrkjus.UPF
> O   16.00    O.pbe-rrkjus.UPF
> ATOMIC_POSITIONS  crystal
> ......
> K_POINTS automatic
> 2  2  1  0  0  0
>
>
>
>
>
> Wei gui
> School of Mechanical Engineering,Chongqing University, China
>
>
>
> _______________________________________________
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> users at lists.quantum-espresso.org
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-- 
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig

Tel:  +49 (0)341 97 36456

email: thomas.brumme at uni-leipzig.de

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