[Wien] Electron density at the nucleus (Electron capture nuclear decay rate work)

[Pavel Novak]

let me comment. I do not recommend to use the Lundin-Eriksson functional. 
While the contact hyperfine field for 3d atoms is improved, we realized 
that it violates important sum rule for the exchange-correlation hole, 
which is imposed by the density functional theory. This brings several 
shortcomings e.g. incorrect energy of the core states. I doubt that any 
local or semilocal Vxc can provide reliable value of the core density at 
the nucleus. For bcc Fe Akai and Kotani (Hyperfine Interactions, 120/121, 
3, 1999 obtained good contact field using the optimised effective 
potential method, but this is computationally expensive.
Regards
Pavel Novak

On Wed, 21 Apr 2010, Laurence Marks wrote:

> A few comments, and perhaps a clarification on what Peter said.
>
> Remember that while Wien2k is more accurate than most other DFT codes,
> it still has approximations with the form of the exchange-correllation
> potential and in how the core wavefunctions are calculated. Hacking by
> applying unphysical constraints so it will match experiments is wrong.
> (Remember the story of the graduate student who matched all properties
> of silicon by tuning the parameters of the DFT calculation for each
> one so it was "right".)
>
> I would instead suggest that you look at better functionals for the
> core wavefunctions, see Novak et al, Phys. Rev. B 67, 140403(R) (2003)
> as well as the papers that cite it and the earlier paper by U. Lundin
> and O. Eriksson, Int. J. Quantum Chem. 81, 247 (2001) and papers that
> cite this. If you ask Peter or Pavel really nicely they may be able to
> provide the code that uses this functional but you will almost
> certainly have to do some coding work. This might not explain your
> experimental results, and if it does not either the experiments are
> wrong or we just don't have good enough theory yet for what you are
> measuring, probably the latter.
>
>

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