Ciao Nicola
You're right, I've mixed two different things too much with a
misleading result. The first information was "use Gaussian smearing
because in my experience makes scf more stable". The second was "if
you use Gaussian smearing and scf_must_converge=.false., then you may
reduce smearing to lower values that avoid the smearing of too much
charge density across the semiconductor band gap (if there is any in
such nanoclusters...), with a partial occupation of orbitals that
should be empty".
Thanks for the clarification, I think it will be useful to Antonio.
Best
Giuseppe
Quoting Nicola Marzari <nicola.marz...@epfl.ch>:
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
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.matti...@ism.cnr.it>
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