[Wien] Hyperfine field

[Azuma, Hideto]

Hello, wien2k experts.

Looking at the :HFF value in scf files, it seems that Wien2k program 
gives us the hyperfine field as 

:HFF = (8pi/3) x 'bohr magneton' x 'spin density at 1st radial point
(:RTO)' ---(a).    (am i right?)

In my recognition, wien2k's LCORE program treat the wave function
 in relativistic sentences even in the usual case ( LSDA or GGA without 
orbital potential nor spin-orbit interaction), so, I am confusing;

1. Does not the spin density diverge at nuclei?
2. How about the validity of formula (a) ?
3. Any good references?

My interests is limited in light atoms like oxygen or lithium now, I
hope
 relativistic effect is negligible in these case, and :HFF's are good
value.
Probably I should learn basic physics more, but I appreciate any
suggestion.


Hideto Azuma, sony corporation.