[Wien] Fermi contact Interaction

[Vladimir Michaelis]

Hello,

   I have a paramagnetic unit cell with a Re with an electron spin of 1 and three other non-paramagnetic ions.  I have built a supercell and have run these calculations a few times using various number of kpoints, magnetic calculations with antiferromagnetic calculations, etc. However, I keep getting a fermi contact of zero, however I know that this is not real.  Are there any known limitations in obtaining the fermi contact terms using this method for Re or Ru? I have also tried Ru and it predicts a rather large value which was slightly counter intuitive from the experimental value recorded.    I am trying to compare these to experimentally determined data that were acquired using NMR, is this the best approach?

PS: Peter I thank you for your previous response however still having a few problems...

	In ionic compounds, the Fermi contact term can sometimes be only a "small" part of the total Hyperfine field. The orbital (and dipolar)
	terms can become large, even for 3d materials, in particular when the
	electronic configuration contains eg. a single 3d electron in one
	spin chanel (eg. high-spin Fe2+). I realize this and have looked into the dipolar and orbital terms however I don't seem to see an affect
	
	However, it is also well known that the contact term is often underestimated by about 10-20% for eg. Fe. - OK 

Also be sure, you do the correct magnetic structure (often they are antiferromagnetic): I have tried this and gets me closure but still not what I was expecting


Regards,

Vlad
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