[Wien] Heusler Alloy Fe2CrSn_Atomic Position

[Gerhard Fecher]

For the 2 structures below, the result should be the same.
as in space group 216 the change of the atoms in positions 4a, 4b  with those on 4c,4d
results in the same symmetry (all positions have Td symmetry)
Occupying 4a,4b or 4c,4d (like you gave below) with the same species will always result in a higher symmetry (Oh) for the other two positions,
and thus into space group 225.

If the Fe atoms have an antiparallel coupling then (as this is not possible in 225) the result of 216 will be different,
otherwise it is identical.

If you exchange in a way that you have for example
Fe: 0.25 0.25 0.25
Cr: 0.75 0.75 0.75
Fe:  0.5   0.5   0.5
Sn: 0.0  0.0   0.0
then this is different from the structures you gave,
and indeed, the magnetic behaviour will be different.

The "exact" structure should be the one with lowest total energy, trivially.

Ciao
Gerhard

EVERYTHING IS SYMMETRY IS EVERYTHING

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von alpa dashora [dashoralpa at gmail.com]
Gesendet: Dienstag, 8. September 2009 05:49
An: wien-request at zeus.theochem.tuwien.ac.at; Wien at zeus.theochem.tuwien.ac.at
Betreff: [Wien] Heusler Alloy Fe2CrSn_Atomic Position

Dear Wien2k Users,

I am trying to calculate the electronic structure of Heusler alloy Fe2CrSn using Wien2k. It is supposed to exist in L2/1 structure (space group 225) with following positions:
Fe: 0.25 0.25 0.25
Fe: 0.75 0.75 0.75
Cr:  0.5   0.5   0.5
Sn: 0.0  0.0   0.0

When the positions are changed as follows:
Fe: 0.0  0.0   0.0
Fe:  0.5   0.5   0.5
Cr: 0.25 0.25 0.25
Sn: 0.75 0.75 0.75

then the Wien shows space group 216 and magnetic properties are totally changed.

Is it right and what is the excact structure for Fe2CrSn?

Please help me.

Thanks in advance,




--
Alpa Dashora