[CPMD-list] NOSE Electrons and Quenching..

[Christel Nonnenberg]

Am Montag, 27. Juni 2005 16:57 schrieb Dave Sherman:
> Dear all,
>
> I'm still fuzzy about the best practice for  applying a thermostat to
> the electrons when doing CP molecular dynamics (on insulators..). The
> tutorial notes I've read suggest letting the system go without NOSE
> ELECTRONS, see what the Ekinc wants to be after, say, 100 steps, and
> thermostating  Ekinc to that value using NOSE ELECTRONS with a
> frequency (in cm-1)  ~ 3 times that of the highest nuclear vibration.
> Someone else in the CPMD list (I forgot who, sorry.. ), said that
> thermostating the electrons  is not necessary or even desired.  I'm
> also very confused about the desired value of EKINC.  For a system with
> 50 H2O molecules and a few Na+ and Cl-'s, how high can EKINC be before
> I start worrying about leaving the BO surface?  If EKINC is too low,
> will the atomic nuclei move too fast and "lose their wavefunctions"?
>
> Does it ever do any harm to quench the electrons back to the BO surface
> every so often during  "production
> mode" of a dynamics run?  Would it be better to not use NOSE ELECTRONS
> and simply apply QUENCH BO ELECTRONS every 5000 or so timesteps?
>
> Thanks for your help!
>
> Dave Sherman


Dear Mr. Sherman,

you will find an answer to most of your questions in:

P.E. Blöchl, M. Parrinello, Phys. Rev. B 45 (16), 9413. 

regards

Christel Nonnenberg 




>
> ______________
> David M. Sherman
> Professor of Geochemistry
> Department of Earth Sciences
> University of Bristol
> Bristol BS8 1RJ UNITED KINGDOM
> Phone: 44-(0)117-954-5446
> http://mineral.gly.bris.ac.uk
>
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-- 
Christel Nonnenberg
Department Chemie und Biochemie
Ludwig-Maximilians-Universität München
Haus E
Butenandtstr. 11
81377 München

Tel.: 089/2180-77602
email:Christel.Nonnenberg at cup.uni-muenchen.de
http://www.cup.uni-muenchen.de/pc/frank/