[Wien] Bi2Se3 atomic positions in wien2k structure file.

[Naseem Hassan]

Thank you Sir, Kroeker. for your illustration. I really appreciate you kind
response.

Thank you once again.
Best Wishes
Naseem


On Fri, Feb 7, 2014 at 1:48 AM, Martin Kroeker <
martin at ruby.chemie.uni-freiburg.de> wrote:

> There is an entire branch of science called "Crystallography". Please do
> not expect us to give the equivalent of a "crystallography 101" lecture in
> a newsgroup.
> In (too) short, atomic positions as well as spacegroup assigments are
> determined
> experimentally, typically by X-ray diffraction.
> And while it is always possible to state which of these atomic positions
> corresponds to which Wyckoff site in the group-theoretical treatment of the
> unit cell symmetry, the reverse is usually not true. (Not all the
> Wyckoff positions need to be occupied, also most have free numeric
> parameters
> x, y, and/or z that are not determined by symmetry considerations anyway).
> Wyckoff position tells you something about symmetry effects at that
> point, and in cases such as your ZnAl2O4 can be used as a shorthand
> notation for the coordinates - Zn on 16c, Al on 8b and O on 32e with
> x=0.25. (Actually the 0.25 is a bit misleading - this is not an exact
> symmetry-imposed number like the 1/8 and 1/2 of the other two sites - it
> might just as well be 0.2473 or something, just that it is the same in
> x,y,z)
> Normally in inorganic chemistry one would learn a few typical crystal
> structures - structure types - that certain key compound classes
> crystallize
> in ("spinel" or "inverse spinel" in your case), and would then be able
> to generate at least an approximate structure from the knowledge that
> something crystallizes in such-and-such structure type.
> For exact coordinates, consult databases and/or original publications.
> --
> Dr. Martin Kroeker            martin at ruby.chemie.uni-freiburg.de
> c/o Prof.Dr. Caroline Roehr
> Institut fuer Anorganische und Analytische Chemie der Universitaet Freiburg
>
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