[Wien] Crystal field splitting

[pieper]

Dear Salman,

unfortunately I have neither means (no Wien2k on my notebook) nor time 
right now to quickly provide an answer to your problems. Anyhow, 
directing you to literature you can cite is probably better than an 
elaborate email lecture on crystal field splittings (not being really an 
expert I am not the ideal person to give such a lecture anyway).

To me the best way to proceed seems to be be:

- get your hands on some textbook on magnetism with a chapter on crystal 
field effects. Kei Yosida: Theory of Magnetism, Springer Series in Solid 
State Science vol 122 might be one choice. Personally, when I ran into 
crystal field effects a rather long time ago, I liked the article of M. 
T. Hutchings: Point charge ... in F. Seitz, D. Turnbull, Solid State 
Physics, vol. 16, p. 227, Academic Press 1964.

- read (understand) that chapter. You should know at this stage which 
parameters appear in the crystal field Hamiltonian if you know L and the 
point symmetry. I did not use Pavel Novaks new package for Wien2k up to 
now but I expect that you can understand its I/O on that basis. And you 
should be aware of the limitations of the concept, especially in a 
3d-metal!

- Find the configuration of B nearest neighbors for the two 
non-equivalent Ni sites in your structure. The idea is that charges 
farther out are pretty much shielded. Simply look at the structure using 
Xcrysden or something similar to identify this configuration. In Wien2k, 
outputnn gives you the number and position of these B atoms. My guess (a 
guess, not more!) is, that one Ni site has a (distorted) octahedral 
configuration, the other a (also distorted) tetrahedral one. CF 
splitting usually is considered in steps of decreasing importance of the 
contribution in the Hamiltonian: first approximate the situation by a 
cubic crystal field, then take into account, say, tetragonal distortions 
of the ideal octahedron, and so on, lowering symmetry in each step.

I hope this helps,

Martin


---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 03.11.2014 13:41, schrieb Salman Zarrini:
> +++++++++++++++++++
> Dear Martin and Delamora,
> 
> Many thanks for your answer, actually, controversial state for me here
>  is "3d" orbitals of Ni elements crystalline together with "boron" in
> a  orthorhombic structure, Pnma space group. I can see different kind
> of  point group in case.outputsgroup(1,1,C1 for sort one, m,m,Cs for
> atom  sort 2 and m,m,Cs for atom sort 3 and a "mmm,2/m,2/m 2/m,D2h" in
> the  end for the whole structure)but I can not make a link between
> them and  potential crystal filed splitting for this structure, for
> convenience  the struct file has been enclosed, I would be thankful if
> you guided  me to find the proper crystal filed.
> 
> Cheers,
> Salman
> +++++++++++++++++++
> 
> 
> 
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