[QE-users] vc-relax Convergence problem with 'TS' VdW correction
Nicola Marzari
nicola.marzari at epfl.ch
Fri Oct 12 21:31:47 CEST 2018
First I would try to have a much, much tighter convergence threshold
than conv_thr = 1.0d-6; I think we use as a standard 0.2d-9 times
the number of atoms - so in your case 4.0d-9, rather than
1.0d-6. If your selfconsistency is poor, your forces are noisy, and the
relaxation slow.
I also note that there is a variable called
ts_vdw_econv_thr ; not sure what it does, but seems relevant.
nicola
On 12/10/2018 16:36, Hooman Yaghoobnejad Asl wrote:
> Dear all,
> I'm experiencing a problem with total force minimization when
> the vdw_corr = 'TS' is used. Without the vdw_corr option, force
> minimization completes smoothly, as shown below:
>
> Total force = 0.144455 Total SCF correction = 0.002938
> Total force = 0.096620 Total SCF correction = 0.004258
> Total force = 0.023833 Total SCF correction = 0.000694
> Total force = 0.013572 Total SCF correction = 0.000196
> Total force = 0.013176 Total SCF correction = 0.000775
> Total force = 0.013520 Total SCF correction = 0.001316
> Total force = 0.013322 Total SCF correction = 0.000670
> Total force = 0.013164 Total SCF correction = 0.000897
> Total force = 0.013634 Total SCF correction = 0.000800
> Total force = 0.016822 Total SCF correction = 0.000639
> Total force = 0.015558 Total SCF correction = 0.000354
> Total force = 0.012359 Total SCF correction = 0.000858
> Total force = 0.009014 Total SCF correction = 0.000322
> Total force = 0.007140 Total SCF correction = 0.000338
> Total force = 0.006073 Total SCF correction = 0.000556
> Total force = 0.005047 Total SCF correction = 0.000465
> Total force = 0.004639 Total SCF correction = 0.000050
> Total force = 0.003113 Total SCF correction = 0.000382
> Total force = 0.002225 Total SCF correction = 0.000268
> Total force = 0.001698 Total SCF correction = 0.000156
> Total force = 0.001505 Total SCF correction = 0.000372
> Total force = 0.001422 Total SCF correction = 0.000244
> Total force = 0.001442 Total SCF correction = 0.000420
> However, after implementing the VdW correction, it seems that the forces
> cannot be minimized further even after 200 ionic steps:
>
> Total force = 0.146620 Total SCF correction = 0.003488
> Total force = 0.108842 Total SCF correction = 0.004843
> Total force = 0.069519 Total SCF correction = 0.000923
> Total force = 0.016339 Total SCF correction = 0.002655
> Total force = 0.015353 Total SCF correction = 0.001041
> Total force = 0.016188 Total SCF correction = 0.000361
> Total force = 0.016350 Total SCF correction = 0.000832
> Total force = 0.015878 Total SCF correction = 0.001654
> Total force = 0.016273 Total SCF correction = 0.000560
> Total force = 0.016349 Total SCF correction = 0.000406
> Total force = 0.015879 Total SCF correction = 0.001403
> .
> .
> .
> .
> Total force = 0.015866 Total SCF correction = 0.001214
> Total force = 0.016279 Total SCF correction = 0.000263
> Total force = 0.016351 Total SCF correction = 0.000394
> Total force = 0.015879 Total SCF correction = 0.000394
> Total force = 0.016277 Total SCF correction = 0.001323
> Total force = 0.016347 Total SCF correction = 0.000194
> Total force = 0.015878 Total SCF correction = 0.000606
> I was wondering if anyone can make a comment on this? I'm using QE 6.2
> on a cluster. Input copied below:
> &CONTROL
> title = 'Li0.5NiO2 NCPP FM VdW ' ,
> calculation = 'vc-relax' ,
> max_seconds = 86300 ,
> ! wf_collect = .true. ,
> outdir = '/' ,
> wfcdir = '/' ,
> pseudo_dir = '/scratch/05246/pseudo/' ,
> !restart_mode = 'restart' ,
> prefix = 'LNO' ,
> disk_io = 'low' ,
> verbosity = 'high' ,
> nstep = 200 ,
> /
> &SYSTEM
> ibrav = 0,
> celldm(1) = 1.889726,
> nat = 21,
> ntyp = 3,
> ecutwfc = 80 ,
> ecutrho = 320 ,
> occupations = 'smearing' ,
> degauss = 0.001 ,
> smearing = 'gaussian' ,
> nspin = 2 ,
> starting_magnetization(1) = 0.25,
> vdw_corr = 'TS' ,
> /
> &ELECTRONS
> electron_maxstep = 500,
> conv_thr = 1.0d-6 ,
> /
> &IONS
> /
> &CELL
> /
> CELL_PARAMETERS {alat}
> 5.790000 0.000000 0.000000
> -1.447500 2.507144 0.000000
> 0.000000 0.000000 14.221000
> ATOMIC_SPECIES
> Ni 58.69000 Ni_ONCV_PBE-1.0.upf
> O 15.99000 O_ONCV_PBE-1.0.upf
> Li 6.94000 Li_ONCV_PBE-1.0.upf
> ATOMIC_POSITIONS crystal
> O 0.000000 0.000000 0.232000
> O 0.000000 0.000000 0.768000
> O 0.333333 0.333333 0.565333
> O 0.333333 0.333333 0.101333
> O 0.166667 0.666667 0.898667
> O 0.166667 0.666667 0.434667
> Ni 0.000000 0.000000 0.500000
> Ni 0.333333 0.333333 0.833333
> Ni 0.166667 0.666667 0.166667
> Li 0.166667 0.666667 0.666667
> O 0.500000 0.000000 0.232000
> O 0.500000 0.000000 0.768000
> O 0.833333 0.333333 0.565333
> O 0.833333 0.333333 0.101333
> O 0.666667 0.666667 0.898667
> O 0.666667 0.666667 0.434667
> Ni 0.500000 0.000000 0.500000
> Ni 0.833333 0.333333 0.833333
> Ni 0.666667 0.666667 0.166667
> Li 0.500000 0.000000 0.000000
> Li 0.833333 0.333333 0.333333
> K_POINTS automatic
> 4 8 2 0 0 0
>
> Thank you
> P.S. I benchmarked the wf cut-off energy vs binary oxides for each metal
> and 80 Ry gave values comparable to 320 Ry.
>
> --
> *Hooman Yaghoobnejad
> *
> *PhD, Department of Chemistry
> *
> *Missouri University of Science and Technology
> *
> *Rolla, MO 65409
> *
> *USA*
>
>
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--
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
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