Correcting myself: stress for meta-GGA is implemented, but only in
the spin-unpolarized case
Paolo
On Thu, Apr 25, 2019 at 8:48 AM Paolo Giannozzi
<p.gianno...@gmail.com <mailto:p.gianno...@gmail.com>> wrote:
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.r...@gmail.com <mailto:gio.pi.r...@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.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.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
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-- 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
--
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
_______________________________________________
Quantum Espresso is supported by MaX
(www.max-centre.eu/quantum-espresso)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
