[Pw_forum] converge problem in calculating the vacancy on TiO2 surfaces
Ari Paavo Seitsonen
ari.p.seitsonen at iki.fi
Sun Mar 1 10:08:11 CET 2009
Dear Vega,
Just my guesses and suggestions: One could try mixing of the density,
like
&electrons
mixing_beta = 0.7
/
(or a value even smaller than 0.7, or some other parametres for the
mixing) since with a defect you might now have defect levels in the band
gap, leading to a more difficult a convergence. Eventually one could also
switch on the broadening of the occupation numbers, eventually switching
it off for the physical/production jobs, but just to check if the problem
in convergence comes due to this.
And in the original paper the authors discuss spin-polarisation, one
might test also this (nspin = 2), with different initial magnetisations
[starting_magnetization(xx) = ...] for the atoms surrounding the defect.
Greetings,
apsi
On Sun, 1 Mar 2009, vega lew wrote:
> Dear all,
>
> I am planning to calculate the Oxygen vacancy properties of TiO2 surfaces.
> The calculation for the ideal surfaces are quite normal and the results are
> in line with the one that literature reported. But, when I tried to
> calculate the anatase 101 surface with an Oxygen vacancy (O2c was removed
> directly from the stoichiometric Anatase 101as described in J. Phys. Chem. C
> 2007, 111, 16397-16404, I encounter the problem of convergence for SCF
> cycle. I tried to add 20% more empty band to the system the problem still
> laid in. How could I overcome the problem?
>
> my input file was attached at the bottom of the mail
>
> thank you for reading. Any hints will be appreciated.
>
> vega
>
...
>
> &SYSTEM
> ibrav = 8,
> celldm(1) =19.3269,
> celldm(2) = 1.1094,
> celldm(3) = 1.7450,
> nat = 71,
> ntyp = 2,
> nosym = .true.,
> ecutwfc = 30,
> ecutrho = 300,
> /
>
> &ELECTRONS
>
> /
>
> &IONS
> ion_dynamics = 'bfgs',
> /
>
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Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
IMPMC, CNRS & Université Pierre et Marie Curie
Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820
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