[Wien] the isomer shifts problem

[liuzw03 at st.lzu.edu.cn]

> >The struct file is added below.
> 
> You have a really 'free' Fe monolayer, not surrounded by anthing. Is 
> that what you want? In that case, you can separate the layers even 
> further by putting a single Fe at Z=0.

Yes.That's what we want.We want to calculate that system which is composed of many
Fe monolayers.If we put a single Fe at Z=0,what will the struct file be?we don't
know how to put it.


> 
> > The isomer shift is the product of a constant and the difference
> > between the
> > density of nucleus at our Fe monolayers and the density of nucleus at
> > bcc-Fe.We
> > get the density at nucleus at Fe monolayers from the SCF files is
> > 15310.698213,and
> > the density at nucleus at bcc-Fe is 15309.668598.So the difference is
> > 1.029615.The
> > constant is about -0.24 whose unit is a0**3 mm/s.So we get the isomer
> > shift is
> > -0.247mm/s.I am puzzled if I have the right density of nucleus.
> 
> What you would need in principle is the density *at* the point 
> position of the nucleus. Unfortunately, WIEN cannot give you that 
> number directly (there is a divergence at the nuclei, due to LDA/GGA, 
> if I'm not mistaken). But you can hope that the density at a point 
> close to the nucleus contains more or less the same information. That 
> is what is given by :RTO. It is the density at a distance R0 from the 
> nucleus, expressed in e/bohr^3 (I think, it is not mentioned 
> explicitely in the UG). R0 is set for each atom in case.struct (and 
> you might want smaller values than the defaults, similar to a typical 
> nuclear radius for Fe). You will see that :RTO *strongly* depends on 
> R0. Clearly, you cannot use the -0.24 (which contains information on 
> the nuclear radius of ground and excited state for 57Fe), which is for 
> a hypothetical R0=0. Solution: plot :RTO calculated for a few simple 
> compounds as a function of the experimental isomer shift (using always 
> the same R0, Rkmax and a converged k-mesh). That will be more or less 
> a linear plot. Fit a straight line, and you can determine now for the 
> calculated :RTO for your monolayer to which experimental isomer shift 
> it corresponds. (have a look for the papers of P.E. Lippens and 
> references therein, he has some works on the isomer shift calculation 
> for 119Sn).
> 
> Stefaan


The -0.24 is come from other literatures which are about calculating the isomer
shifts using the 57Fe.But maybe I choose a different R0 from others works.I will
try to fix it.
Thank you very much!!!
Best wishes!


your sincerely,
Zaiwen 
> 
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