[QE-users] Structure optimization using rvv10-scan

[Paolo Giannozzi]

I am not sure that the calculation of stress is implemented with meta-GGA.

SCAN behaves better than other meta-GGA, but still it is numerically
unstable. See for instance here:  https://gitlab.com/QEF/q-e/issues/32.
Before trying difficult calculations with SCAN you should verify whether
you can do simple ones.

Paolo


On Sat, Apr 20, 2019 at 3:33 AM Giovani Rech <gio.pi.rech at gmail.com> wrote:

> Hello all,
>
> Have anyone tried structure optimization using rvv10-scan?
>
> I'm trying to optimize a structure (graphite) at 0.0 kbar taking into
> account van der Waals interactions. For such, I'm using the SCAN+rVV10 by
> setting "input_dft = 'rvv10-scan'". What I'm getting as a result makes no
> sense, with unreasonable pressures. Here's a plot of the pressure and
> volume as a function of optimization step:
> [image: image.png]
>
> When I got this values I was using version 6.4.0 and then tried again with
> 6.3 and finally with the latest version, 6.4.1, and got the same values
> (plotted above). Here's the input that I used:
>
> &CONTROL
>>                        title = "graphite_rvv10_vcrelax" ,
>>                  calculation = 'vc-relax' ,
>>                 restart_mode = "from_scratch" ,
>>                       outdir = "./" ,
>>                   pseudo_dir = "/home/giovani/graphite/pseudo" ,
>>                       prefix = "gC" ,
>>                      disk_io = 'default' ,
>>                    verbosity = 'default' ,
>>                etot_conv_thr = 1.0D-4 ,
>>                forc_conv_thr = 1.0D-3 ,
>>                        nstep = 400 ,
>>                      tstress = .true. ,
>>                      tprnfor = .true. ,
>>  /
>>  &SYSTEM
>>                            A = 2.47000e+00 ,
>>                            C = 8.68000e+00 ,
>>                          nat = 4,
>>                         ntyp = 1,
>>                      ecutwfc = 80 ,
>>                      ecutrho = 320 ,
>>                    input_dft = 'rvv10-scan' ,
>>                        ibrav = 4 ,
>>  /
>>  &ELECTRONS
>>             electron_maxstep = 200,
>>                     conv_thr = 1.00000e-06 ,
>>                  startingpot = "atomic" ,
>>                  startingwfc = 'atomic' ,
>>                  mixing_mode = "plain" ,
>>                  mixing_beta = 7.00000e-01 ,
>>                  mixing_ndim = 8,
>>              diagonalization = 'david' ,
>>               diago_thr_init = 1e-4 ,
>>  /
>>  &IONS
>>                 ion_dynamics = 'bfgs' ,
>>                ion_positions = 'from_input' ,
>>                      upscale = 100 ,
>>             trust_radius_max = 1.0D-3 ,
>>  /
>>  &CELL
>>                cell_dynamics = 'bfgs' ,
>>                        press = 0.0 ,
>>               press_conv_thr = 0.05 ,
>>                  cell_factor = 1.2 ,
>>  /
>> ATOMIC_SPECIES
>>     C  12.0107  C.SR.ONCVPSP.PBEsol.stringent.upf
>> ATOMIC_POSITIONS crystal
>> C 0.0000000000 0.0000000000 0.000000000
>> C 1/3          2/3          0.000000000
>> C 1/3          2/3          1/2
>> C 2/3          1/3          1/2
>> K_POINTS automatic
>>   6 6 2   0 0 0
>
>
> I then tried the same optimization using PBE, by just commenting the
> 'input_dft' line, and got values of both pressure and volume converging to
> fairly reasonable values (as plotted below) which makes me think that the
> problem might be with the rVV10-scan option. Have anyone else had this kind
> of problem? Any ideas on how this could be fixed?
> [image: image.png]
>
> Also, when testing and comparing the results of both approaches with
> verbosity=high to investigate which contribution to the pressure was wack,
> I noticed that almost all the pressure matrices were more or less similar,
> except for 'exc-cor stress', that was of the same order of magnitude but
> opposite signs, and 'core-core stress', which was off both in magnitude and
> in sign. I'm not sure if this is relevant to the problem, but I thought it
> could help in finding a solution.
>
> Thank you for your attention,
> Best regards,
> Giovani Rech
>
> Universidade de Caxias do Sul,
> Caxias do Sul - RS, Brazil
>
> _______________________________________________
> Quantum Espresso is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users



-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20190425/43001fe9/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 33073 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20190425/43001fe9/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 71488 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20190425/43001fe9/attachment-0001.png>