<div dir="ltr"><div>Answering myself: it's the combination "variable cell + Tkatchenko-Scheffler" that doesn't work properly</div><div><br></div><div>PG<br></div></div><br><div class="gmail_quote"><div dir="ltr">On Sat, Oct 13, 2018 at 6:46 PM Paolo Giannozzi <<a href="mailto:p.giannozzi@gmail.com">p.giannozzi@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>I don't think a tighter convergence threshold will fix the problem here: there is a mismatch between forces and energies. This calculation uses</div><div>- Tkatchenko-Scheffler corrections</div><div>- in a spin-polarized case<br></div><div>- in a variable-cell calculation</div><div>Assuming that there is no problem without TS, it would be helpful to know whether the problem is due to spin polarization, to variable cell, to both, or to none.</div><div><br></div><div>PG<br></div><div> </div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Oct 12, 2018 at 9:32 PM Nicola Marzari <<a href="mailto:nicola.marzari@epfl.ch" target="_blank">nicola.marzari@epfl.ch</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
First I would try to have a much, much tighter convergence threshold<br>
than conv_thr = 1.0d-6; I think we use as a standard 0.2d-9 times<br>
the number of atoms - so in your case 4.0d-9, rather than<br>
1.0d-6. If your selfconsistency is poor, your forces are noisy, and the<br>
relaxation slow.<br>
<br>
I also note that there is a variable called<br>
ts_vdw_econv_thr ; not sure what it does, but seems relevant.<br>
<br>
nicola<br>
<br>
<br>
<br>
<br>
On 12/10/2018 16:36, Hooman Yaghoobnejad Asl wrote:<br>
> Dear all,<br>
> I'm experiencing a problem with total force minimization when <br>
> the vdw_corr = 'TS' is used. Without the vdw_corr option, force <br>
> minimization completes smoothly, as shown below:<br>
> <br>
> Total force = 0.144455 Total SCF correction = 0.002938<br>
> Total force = 0.096620 Total SCF correction = 0.004258<br>
> Total force = 0.023833 Total SCF correction = 0.000694<br>
> Total force = 0.013572 Total SCF correction = 0.000196<br>
> Total force = 0.013176 Total SCF correction = 0.000775<br>
> Total force = 0.013520 Total SCF correction = 0.001316<br>
> Total force = 0.013322 Total SCF correction = 0.000670<br>
> Total force = 0.013164 Total SCF correction = 0.000897<br>
> Total force = 0.013634 Total SCF correction = 0.000800<br>
> Total force = 0.016822 Total SCF correction = 0.000639<br>
> Total force = 0.015558 Total SCF correction = 0.000354<br>
> Total force = 0.012359 Total SCF correction = 0.000858<br>
> Total force = 0.009014 Total SCF correction = 0.000322<br>
> Total force = 0.007140 Total SCF correction = 0.000338<br>
> Total force = 0.006073 Total SCF correction = 0.000556<br>
> Total force = 0.005047 Total SCF correction = 0.000465<br>
> Total force = 0.004639 Total SCF correction = 0.000050<br>
> Total force = 0.003113 Total SCF correction = 0.000382<br>
> Total force = 0.002225 Total SCF correction = 0.000268<br>
> Total force = 0.001698 Total SCF correction = 0.000156<br>
> Total force = 0.001505 Total SCF correction = 0.000372<br>
> Total force = 0.001422 Total SCF correction = 0.000244<br>
> Total force = 0.001442 Total SCF correction = 0.000420<br>
> However, after implementing the VdW correction, it seems that the forces <br>
> cannot be minimized further even after 200 ionic steps:<br>
> <br>
> Total force = 0.146620 Total SCF correction = 0.003488<br>
> Total force = 0.108842 Total SCF correction = 0.004843<br>
> Total force = 0.069519 Total SCF correction = 0.000923<br>
> Total force = 0.016339 Total SCF correction = 0.002655<br>
> Total force = 0.015353 Total SCF correction = 0.001041<br>
> Total force = 0.016188 Total SCF correction = 0.000361<br>
> Total force = 0.016350 Total SCF correction = 0.000832<br>
> Total force = 0.015878 Total SCF correction = 0.001654<br>
> Total force = 0.016273 Total SCF correction = 0.000560<br>
> Total force = 0.016349 Total SCF correction = 0.000406<br>
> Total force = 0.015879 Total SCF correction = 0.001403<br>
> .<br>
> .<br>
> .<br>
> .<br>
> Total force = 0.015866 Total SCF correction = 0.001214<br>
> Total force = 0.016279 Total SCF correction = 0.000263<br>
> Total force = 0.016351 Total SCF correction = 0.000394<br>
> Total force = 0.015879 Total SCF correction = 0.000394<br>
> Total force = 0.016277 Total SCF correction = 0.001323<br>
> Total force = 0.016347 Total SCF correction = 0.000194<br>
> Total force = 0.015878 Total SCF correction = 0.000606<br>
> I was wondering if anyone can make a comment on this? I'm using QE 6.2 <br>
> on a cluster. Input copied below:<br>
> &CONTROL<br>
> title = 'Li0.5NiO2 NCPP FM VdW ' ,<br>
> calculation = 'vc-relax' ,<br>
> max_seconds = 86300 ,<br>
> ! wf_collect = .true. ,<br>
> outdir = '/' ,<br>
> wfcdir = '/' ,<br>
> pseudo_dir = '/scratch/05246/pseudo/' ,<br>
> !restart_mode = 'restart' ,<br>
> prefix = 'LNO' ,<br>
> disk_io = 'low' ,<br>
> verbosity = 'high' ,<br>
> nstep = 200 ,<br>
> /<br>
> &SYSTEM<br>
> ibrav = 0,<br>
> celldm(1) = 1.889726,<br>
> nat = 21,<br>
> ntyp = 3,<br>
> ecutwfc = 80 ,<br>
> ecutrho = 320 ,<br>
> occupations = 'smearing' ,<br>
> degauss = 0.001 ,<br>
> smearing = 'gaussian' ,<br>
> nspin = 2 ,<br>
> starting_magnetization(1) = 0.25,<br>
> vdw_corr = 'TS' ,<br>
> /<br>
> &ELECTRONS<br>
> electron_maxstep = 500,<br>
> conv_thr = 1.0d-6 ,<br>
> /<br>
> &IONS<br>
> /<br>
> &CELL<br>
> /<br>
> CELL_PARAMETERS {alat}<br>
> 5.790000 0.000000 0.000000<br>
> -1.447500 2.507144 0.000000<br>
> 0.000000 0.000000 14.221000<br>
> ATOMIC_SPECIES<br>
> Ni 58.69000 Ni_ONCV_PBE-1.0.upf<br>
> O 15.99000 O_ONCV_PBE-1.0.upf<br>
> Li 6.94000 Li_ONCV_PBE-1.0.upf<br>
> ATOMIC_POSITIONS crystal<br>
> O 0.000000 0.000000 0.232000<br>
> O 0.000000 0.000000 0.768000<br>
> O 0.333333 0.333333 0.565333<br>
> O 0.333333 0.333333 0.101333<br>
> O 0.166667 0.666667 0.898667<br>
> O 0.166667 0.666667 0.434667<br>
> Ni 0.000000 0.000000 0.500000<br>
> Ni 0.333333 0.333333 0.833333<br>
> Ni 0.166667 0.666667 0.166667<br>
> Li 0.166667 0.666667 0.666667<br>
> O 0.500000 0.000000 0.232000<br>
> O 0.500000 0.000000 0.768000<br>
> O 0.833333 0.333333 0.565333<br>
> O 0.833333 0.333333 0.101333<br>
> O 0.666667 0.666667 0.898667<br>
> O 0.666667 0.666667 0.434667<br>
> Ni 0.500000 0.000000 0.500000<br>
> Ni 0.833333 0.333333 0.833333<br>
> Ni 0.666667 0.666667 0.166667<br>
> Li 0.500000 0.000000 0.000000<br>
> Li 0.833333 0.333333 0.333333<br>
> K_POINTS automatic<br>
> 4 8 2 0 0 0<br>
> <br>
> Thank you<br>
> P.S. I benchmarked the wf cut-off energy vs binary oxides for each metal <br>
> and 80 Ry gave values comparable to 320 Ry.<br>
> <br>
> -- <br>
> *Hooman Yaghoobnejad<br>
> *<br>
> *PhD, Department of Chemistry<br>
> *<br>
> *Missouri University of Science and Technology<br>
> *<br>
> *Rolla, MO 65409<br>
> *<br>
> *USA*<br>
> <br>
> <br>
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<br>
-- <br>
----------------------------------------------------------------------<br>
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL<br>
Director, National Centre for Competence in Research NCCR MARVEL, EPFL<br>
<a href="http://theossrv1.epfl.ch/Main/Contact" rel="noreferrer" target="_blank">http://theossrv1.epfl.ch/Main/Contact</a> <a href="http://nccr-marvel.ch/en/project" rel="noreferrer" target="_blank">http://nccr-marvel.ch/en/project</a><br>
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<a href="https://lists.quantum-espresso.org/mailman/listinfo/users" rel="noreferrer" target="_blank">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote></div><br clear="all"><br>-- <br><div dir="ltr" class="m_-172404073808454035gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>Phone +39-0432-558216, fax +39-0432-558222<br><br></div></div></div></div></div>
</blockquote></div><br clear="all"><br>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>Phone +39-0432-558216, fax +39-0432-558222<br><br></div></div></div></div></div>