[Wien] crystal field splitting

[Víctor Luaña Cabal]

On Sun, Aug 23, 2015 at 07:51:33PM +0000, Lan, Wangwei wrote:
> Dear Wien2k user:
> 
> 
> I am very new in WIEN2k. Now I am running case on our crystal system
> which contains a transition metal Cr. I am particularly interested in
> the d orbital splitting, the energy levels of 5 d orbitals. Does anyone
> know how to calculate the orbital splitting using WIEN2k?

Wangwei,

The answer is not simple and there can be more than one opinion living
around. Let me express mu 0.02 euros.

Crystal field splitting parameters (delta-D, i.e. t2g-eg splitting, Racah
parameters, etc) is by fitting a model to the theoretical or experimental
true calculations of total energy diferences between correlated
electronic states. In other terms, there are no such a thing as
orbital splitting as a well defined element. The orbital approach is
a interpretative description, not a physical definition.

There are decades that I not contribute to this old subject and I
reccomend you to follow the more recent papers by Profs. Luis Seijo and
Zoila Barandiarán, from the UAM (Universidad Aotónoma de Madrid).
You will find in their work a good description of old and modern
treatments, laike MOLCAS calculations, relativity contributions, and
the huge importance of large correlation treatments. Both contribute
to the development of MOLCAS.

<http://www.uam.es/personal_pdi/ciencias/lseijo/>
<http://www.uam.es/personal_pdi/ciencias/yara/>

Notice that the field emerged from dealing with impurities within
crystals, so most of the evolution that I learned was releted to
the moleculartreatment of embedded impurities neighborhoods.

On a solid state perspective, and your mention of wannier functions
lets me thing you may prefer that, notice that d-d, d-s and d-p
transitions correspond to heavily correlated problems, and the wave
funcion perspective has a much longer tradition than TD-DFT ones,
but let me just say that I know less abiout them. The conferences
by  Stefano Baroni on the calculation of the color of natural dies
are simple awesome.

<http://stefano.baroni.me/presentations.html>

Best regards and good luck if you come new to this field,
                                    Dr. Vñictor Luaña
--
     .  .    "In science a person can be convinced by a good argument.
    / `' \   That is almost impossible in politics or religion"
   /(o)(o)\  (Adapted from Carl Sagan)
  /`. \/ .'\  "Lo mediocre es peor que lo bueno, pero también es peor
 /   '`'`   \ que lo malo, porque la mediocridad no es un grado, es una
 |  \'`'`/  | actitud" -- Jorge Wasenberg, 2015
 |  |'`'`|  | (Mediocre is worse than good, but it is also worse than
  \/`'`'`'\/  bad, because mediocrity is not a grade, it is an attitude)
===(((==)))==================================+=========================
! Dr.Víctor Luaña, in silico chemist & prof. ! I hate the bureaucracy
! Departamento de Química Física y Analítica ! imposed by companies to
! Universidad de Oviedo, 33006-Oviedo, Spain ! which I owe nothing:
! e-mail:   victor at fluor.quimica.uniovi.es   ! amazon, ResearchGATE and
! phone: +34-985-103491  fax: +34-985-103125 ! the like.
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