[Wien] xcrysden large multipler k-points

[محمد ارشد فرحان]

actually, i used only 300 k-points and this specific problem arose when i
tried to select k-path for band structure calculations.
my system has monoclinic symmetry so there are a couple of special points
in k-path i wanted to adopt with coordinates like (0.64xxx, 0.32xxx, 0.5).
i selected the total number of divisions (k-points) of this path again 300.
the code insists on having an integer coordinate with a multiplier. for 300
k-points, the multiplier was quite large and the integer coordinates
printed in case.klist_band file were ******.

Prof. Tone asked for my structure file and he too got into same error. Let
me copy - paste his reply:


"On Mon, 2012-07-16 at 17:37 +0900, محمد ارشد فرحان wrote:
> here are the .struct file and complete .klist_band file.
> i tried to solve this problem by making separate kpath klist files for
> every two points. the idea was to join them manually & use different
> multipliers for different path.

Yes, you are right. I could reproduce your problems. I believe that the
problem is due to Wien2K. Your case is a nasty case for Wien2K. Why?
Because it insist on representing the real number (rational number)
as the fraction p/q of two integers with a fixed format. As your case is
not a high symmetry case, the p & q numbers are simple too large and the
stars (****) are displayed.

As a work-around: you could use the coordinates of special k-points as
given by xcrysden, and then you need to construct out of that
semi-manually a klist file suitable for Wien2K (this would involve some
manual editing + some small scripting to interpolate points between
pairs of special k-points).

Regards. Tone

-- 
Anton Kokalj
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
(tel: +386-1-477-3523 // fax:+386-1-477-3822)"

so, therefore i thought may be it is due to same problem you guys are
discussing, & just pushed my mail  . . . . ;D

any way, thnx. for ur reply.

M. Arshad Farhan




On Mon, Jul 30, 2012 at 3:32 PM, Gavin Abo <gsabo at crimson.ua.edu> wrote:

>  What large values did you use in xcrysden for the multiplier and
> k-points?  Someone else might be able to comment on whether you can use
> smaller values and still get accurate results.
>
> I see your posts on the xcrysden mailing list:
>
> http://www.democritos.it/pipermail/xcrysden/2012-July/001215.html
> http://www.democritos.it/pipermail/xcrysden/2012-July/001223.html
>
> From the posts, it looks like the number of k-points you used is possibly
> greater than 99672.  You currently cannot use
>
> multipiler*k-points > 5-digits (i.e., 99,999)
>
> If the larger outputted values are really needed, it could probably be
> done by changing all the "4I5" to say "4I8" in F/kPath.f that is in the
> xcrysden source package (xcrysden-1.5.53.tar.gz).  However, you have to
> compile the xcrysden code.  There are some useful instructions on the web
> for compiling the xcrysden source in Debian or Ubuntu (
> https://sites.google.com/site/jamesanalytis/xcrysden-in-ubuntu-10-04),
> but have not seen for other Linux distributions if one wants to attempt it.
>
> Since your not quite a "linux guy", you will probably want to send your
> struct file (while providing also the multiplier and k-points value used)
> to Tone as requested on the xcrysden mailing list so that a linux binary
> package with changes can be provided if needed.
>
> On 7/29/2012 7:54 PM, محمد ارشد فرحان wrote:
>
> Dear Prof. Lawrance & Gavin-Abo,
>
> i've not tested the latest version of Wien2k but, let me mention one more
> place where real*4 are used that is in the creation of case.klist_band.
>
> for any complicated coordinate in the k-path (mainly in monoclinic
> systems) by using Xcrysden, the multiplier goes shooting high and
> coordinate value exceeds real*4 consequently printing ****** in places of
> k-point coordinates in case.klist_band file.
>
> the XcrySden developers claim it to be on part of Wien2k where it insists
> on real value but restricts it to 4 digits.
>
> if possible, please also look into it and of-course suggest me a solution
> as i'm quite not a linux guy.
>
> regards,
>
>
>
> _______________________________________________
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> Wien at zeus.theochem.tuwien.ac.at
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>
>


-- 
*محمد ارشد فرحان*
Dept of Chemistry,
Pohang Univ of Sci & Tech
Pohang, Republic of Korea
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