Hello Francesco,
Adding to the previous posts, I found a better convergence in systems
with vacuum using
mixing_mode = 'local-TF'
Personally I do not find using 'conv_thr = 1e-8' as very strict, this is
what I usually use for relaxation (and a bit tighter still when going for
phonons etc), but indeed one might save some iterations, in particular at
the beginning of the relaxation. Did you check that your electronic
structure (density of states for example) looks as expected, for example
having a band gap if such is expected?
And personal opinion again, I would be surprised if the bad convergence
is due to 50 Ry being too low, as those elements, in particular C, H and
O, should be fine already at 35-40 Ry, not to mention 50. I can just
imagine that the vdW-DF is extremely sensitive to some noise that arises
from the augmentation charges, that was maybe not an issue when those
pseudo potentials were first adapted in calculation (ie using "plain GGA"
or LDA).
Greetings,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
On Mon, 23 Jan 2017, Francesco Pelizza wrote:
Hello dear community,
Here in strathclyde some colleagues are using QE to relax and than study
some MOF's.
The problem starts from the beginning, no convergence in the first SCF
cycle before a fixed cell relaxation.
We took care of spin polarized calculation, switched to non polarized
calculation and many other things, WFC from 50 to 80 Ry and RHO cutoffs
10 times the WFC, with gamma sampling and 3 x 3 x 3.
Also checked the smearing, degauss values, nothing seemed to make the
convergence better.
Here you can find some input files and output files.
We used ultrasoft pseudopotentials applying PBE and then vdW-DF functionals.
No success at all.
Please some of you have better experience of us in these systems to tell
us what we do wrong?
BW
Francesco Pelizza and Chris Campbell
Strathclyde University
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