On 13/05/2024 17:26, Giuseppe Mattioli wrote:
occupations= 'smearing'
smearing= 'cold'
degauss= 0.05 ! I know it's quite large, but necessary to
stabilize the SCF at this preliminary stage (no geometry step done yet)
mixing_beta= 0.4
If you want to stabilize the scf it is better to use a Gaussian smearing
and to reduce degauss (to 0.01) and mixing beta (to 0.1 or even
0.05~0.01). In the case of a relax calculation with a difficult first
step, try to use scf_must_converge=.false. and a reasonable
electron_maxstep (30~50). It often helps when the scf is not completely
going astray.
Ciao Giuseppe, I would agree that in a semiconductor it might be more
natural to use Gaussian (although even for cold things are now sorted
out -
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.107.195122); but
I wonder why reducing the smearing would help convergence.
To me, the smaller the smearing the more you can be affected by
level-crossing instabiities?
nicola
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, SNSF
Head, Laboratory for Materials Simulations, Paul Scherrer Institut
Contact info and websites at http://theossrv1.epfl.ch/Main/Contact
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