[Wien] more about tisi2

[Vicki Keast]

Dear All,

Further to my previous email about having trouble getting TiSi2. The 
generation of additional and wrong atoms was probably due to us entering 
the structure incorrectly. However we are still having trouble getting 
this structure to work.

One unusual characteristic is that although the y lattice parameter is 
different to the x lattice parameter, and stays this way in the the text 
of the structure file, when we look at the structure file through w2web, 
they are the same. And if you then save it through w2web, they are 
overwritten as the same.

Another thing I don't understand is that when we run kgen, the number of 
k-points in all three directions is the same, even though the y-lattice 
parameter is nearly half the length of the other two.

Finally the scf cycle will not run and lapw0.error has the following 
information.

'SETFF1'- ifft too small in xcpot3
'SETFF1' - 2*(KKK+1) LARGER THAN IFFT PARAMETERS IN XCPOT3
'SETFF1' - KKK= 0 0 30
'SETFF1' - IIx= 0 0 30
'SETFF1' - IFFT=  64  64  60 


We have also tried directly putting in all the atom positions and 
letting wien sort out the space group and symmetry, which it does as we 
would expect except for a shift of the origin. In this case the lattice 
parameters at least stay as they should be, but we still get an 
identical error to the one above when we try the scf cycle.

The structure is 70 Fddd (a=8.27, b = 4.80, c=8.55) Ti at 1/8, 1/8, 1/8 
and Si at 0.4615, 1/8, 1/8.

As I only receive the weekly digest, could any responses be sent 
directly to me as well.

Thanks and best regards,
Vicki
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Dr. Vicki J. Keast
School of Mathematical and Physical Sciences
The University of Newcastle
Callaghan NSW 2308
Australia
Ph: + 61 2 4921 6653
Fax: + 61 2 4921 6907
email: vicki.keast at newcastle.edu.au
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