Queries about input and output files, running specific calculations, etc.
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asif_ali28
- Newbie
- Posts: 9
- Joined: Tue Apr 05, 2022 12:18 pm
#1
Post
by asif_ali28 » Thu Sep 26, 2024 7:10 am
Hello everyone,
I am performing a SCF calculation for a nanoparticle of size 9x10x11Ang^3 (72 atoms) and 5 Ang vacuum in all three directions. Even after long SCF run the convergence does not reach below 0.1E0. I have tried increasing NBANDS and ENCUT, but could not reach the convergence even after few hundreds SCF cycles. I would be grateful for your kind help and suggestions.
INCAR:
Code: Select all
ISTART = 1
ISPIN = 1
LREAL = .FALSE.
ENCUT = 320
LWAVE = .TRUE.
LCHARG = .TRUE.
KPAR = 1
NCORE = 6
ISMEAR = 0
SIGMA = 0.05
NELM = 200
EDIFF = 1E-05
K-point: 1x1x1
Thankyou
Regards,
Asif Ali
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martin.schlipf
- Global Moderator
- Posts: 542
- Joined: Fri Nov 08, 2019 7:18 am
#2
Post
by martin.schlipf » Thu Sep 26, 2024 2:16 pm
There are a couple of things you can try:
use a different electronic optimizer (ALGO), sometimes CG methods can proceed where Davidson fails
try to play around with the mixing parameters in particular (BMIX, this in particular relevant if you see that a optimization at constant charge (ICHARG=12) works
you mentioned that you considered a different ENCUT, please check that it aligns with the ENMAX value(s) in your POTCAR
visualize the structure or look at the neighbor list in the OUTCAR file to make sure the structure is set up correctly
it is also a good idea to try a simpler system (less vacuum, smaller nanoparticle) which should converge simpler and may help you to learn techniques to improve convergence at a smaller computational cost
If none of this advice helps, please get back to me.
Martin Schlipf
VASP developer