[Wien] Fixed-Magnetic-Moment

[Peter Blaha]

On Sat, 28 Feb 2004, rosangela de paiva wrote:

>
> Dear prof. P. Blaha,
>
> We have tried a fixed-magnetic-moment calculation for a system containing
> 17 valence electrons, constraining the total spin magnetic moment to 5 Bohr
> magneton.
>
> We found some puzzles in the output:
>
> i- Apparently the program carry out calculations considering 17+5=22 and
> also 17-5=12 electrons. Why?

When doing spin-up you want to have 22/2=11 electrons, while for
spin-dn you need 12/2=6 electrons. This gives the desired N-tot=17 and
n-up - n-dn=5

> ii- The occupation of the eigenvalues, both up and down, up to the
> Fermi energy, do not fit to the total magnetic moment found by the
> program after each iteration.
>
> iii- Anyway, how does this FSM options work?

First you calculate only spin-up  (x lapw1 -up). The corresponding
eigenvector is copied to spin-dn !!! and   x lapw2 -up
runs with "22" electrons. This yields a spin-up density containing 11 e
and a Fermi-energy for spin-up (and related occupations).

Afterwards,  x lapw1 -dn  runs and vectordn is copied to vectorup.
x lapw2 -dn calculates the spin-dn charge, with a different !!! E-fermi
and thus different occupations.

NOTE: After a runfsm calculation both eigenvectors contain spin-dn !! and
you will be surprised when you plot the DOS,....
You must run    x lapw1 -up again, x lapw2-up -qtl; x lapw2 -dn -qtl
and then put manually the two different E-fermi (from case.scf) into
case.qtlup/dn respectively.

Regards
                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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