[Wien] problem WZ structure (p63mc)

[David Holec]

Hello,

The structure you use is OK and is basically the same as the one I use
(apart from a slightly different u which may change from case to case as for
example lattice parameters do). Just be careful, I think the z-coordinates
of both nitrogen atoms should be the same but 0.5 apart, i.e. 0.384 and
0.884 (not 0.8848 as you have).

The meaning of the structure from the web is exactly the same as your
structure with just a little bit different position for one of the two
nitrogen atoms. To my best understanding, your definition and this one from
the web are equivalent and will generate the same structure. Basically,
instead of the z-coordinate for the second nitrogen atom (0.884) you use its
equivalent position (given by the periodicity of the structure)
0.884-1=-0.116. This value is different from the one given on the website
and therefore I suspect a mistake on the web?

The last definition don't generate a unit cell of wurtzite AlN. Of course,
you can use such positions, that one of the atoms is at the origin (0,0,0)
but in that case all other positions should change accordingly (and the only
difference between such positions and your structure would be an addition of
a constant vector). Isn't it possible that you have misunderstood Dridi's
paper?

I hope this is helpful.
All the best,
David


__________________________________________________

David Holec               
Department of Materials Science & Metallurgy
University of Cambridge
Pembroke Street
CB2 3QZ, U.K.   

Tel: +44 (0) 1223 334404
Email: dh331 at cam.ac.uk
__________________________________________________





-----Original Message-----
From: wien-bounces at zeus.theochem.tuwien.ac.at
[mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of U P Verma
Sent: Tuesday, August 28, 2007 11:08 AM
To: A Mailing list for WIEN2k users
Subject: [Wien] problem WZ structure (p63mc)

would any body please suggest me exact position of AlN structure in WZ phase
(space group) as 186 p63mc

Presently I am using
Al
0.333333 0.66666666 0.000000
0.666666  0.3333333 0.500000

N

0.33333  0.666666  0.384000
0.66666  0.333333  0.884800

Is it ok for WZ structure

I am confused as different litt. have Diff. position

In nrl website it is
0.333333 0.66666666 0.000000
0.666666  0.3333333 0.500000

0.33333  0.666666  0.384000
0.66666  0.333333  -0.125200

And in Z Dridi paper it is
0.000000 0.00000000 0.000000
0.666666  0.3333333 0.500000

0.33333  0.666666  0.384000
0.66666  0.333333  0.884800

When I used these position and save the structure it automatically change Al
position as:

0.000000 0.00000000 0.000000
0.000000  0.0000000 0.500000

Please help me 

With regards
P.S Bisht





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