[Pw_forum] SCF loop fails to converge when tefield is switched on

[soroush pakseresht]

Dear Paolo,

In my calculations, the sawtooth potential is defined as follows
                           edir = 3 ,
                        eamp = 0.0005834 ,
                     emaxpos = 0.75 ,
                      eopreg = 0.4  ,
The emaxpos is slightly above the topmost layer of the slab and
 (emaxpos+eopreg-1) is just below the bottom layer. Basically this should
correspond to a sawlike potential linearly increasing from one end to the
other end of the slab without any sign change. So, I don't think this should
be the reason for my problem.

Soroush

On Fri, Dec 17, 2010 at 2:49 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:

> soroush pakseresht wrote:
>
> > I consider a saw-like electric field (as large as 0.0005 au~0.03 eV/A)
> > exerted along c-axis of my hexagonal unit cell[...] the calculation [...]
> > becomes slower and slower and eventually ends up with a dE much larger
> > than conv_thr
>
> are you sure that your sawtooth potential doesn't changs sign in the
> middle of atoms? misunderstanding of the form of the sawtooth potential
> is a frequent reason for bad or no convergence
>
> P.
> --
> Paolo Giannozzi, Democritos and University of Udine, Italy
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-- 
Soroush Pakseresht
Advanced Science Institute (RIKEN)
Saitama-Japan
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