[Wien] please help

[susanta mohanta]

Dear Prof Peter Blaha,
I have calculated spin polarised calculation in Gd(2*2*2)for Cd
impurity and the results,hyperfine field, magnetic moment,electric
field gradient reasonably matches with available literature.actually
I am interested to find out the electric field gradient of Cd in Gd at room
temperature which is paramagnetic, and thats why I have started unpolarised
calculation,and faced the problem.So how to proceed in this regard?

with regards
Susanta kumar Mohanta


On Tue, Sep 16, 2008 at 10:51 AM, Peter Blaha
<pblaha at theochem.tuwien.ac.at>wrote:

> I'm not surprised that a Gd-supercell does NOT converge in an
> unpolarized calculation.
>
> You have to consider the underlying physics: Gd metal has 7 4f
> electrons, thus in a polarized calculation this gives a rather stable
> situation, i.e. "all" 7 spin-up states are occupied, but all 7 spin-dn
> states empty.
> In an unpolarized case you must put 7 electrons into "3.5 states" (each
> state takes now 2 electrons!) and it is rather naturally that this will
> cause problems.
>
> The VERY efficient mixer seems to manage this for pure Gd, but in the
> supercell there are many more degrees of freedom and thus convergence is
> much more difficult. Eventually, switching to TEMP and a rather large
> broadening will help to converge.
>
> In any case, you have to ask yourself: what should this calculation be
> good for ?? Even above the Neel/Curie-point one has local magnetic
> moments (only the long range order has gone).
>
> susanta mohanta schrieb:
> >
> > Dear all,
> >
> > I have finished spin polarised calculation for Gd(2*2*2 supercell) with
> Cd
> > impurity.But When I started with same structure for unpolarised
> calculation
> > with RKMAX=7.5:GMAX=14 and 300kpoints(to begin with),the computation
> > doesn;t seems to converge.After 200 cycle we noticed that both charge and
> > energy are oscillating.So please help me in this regard.I have also
> > calculated
> > unpolarised calculation for pure Gd.So what may be the problem?
> >
> > with regards
> > susanta
> >
> > --
> > SUSANTA K MOHANTA
> > RESEARCH SCHOLAR
> > DEPT.OF PHYSICS
> > IIT KHARAGPUR
> > *****************************
> >
> >
> > ------------------------------------------------------------------------
> >
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-- 
SUSANTA K MOHANTA
RESEARCH SCHOLAR
DEPT.OF PHYSICS
IIT KHARAGPUR
*****************************
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