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Dear Dr. Stefaan and Georg,<br><br>
It is definitely very interesting for me to know about this. I
deeply thank you for your help. <br><br>
Have a nice day.<br><br>
Regards,<br>
Khuong<br><br>
<br>
At 04:55 PM 6/14/2005, you wrote:<br>
<blockquote type=cite class=cite cite="">
<blockquote type=cite class=cite cite="">I'm no expert on these supercell
calculations, but I guess the density of<br>
k-points should be the same.<br>
This means that if you you use 2000 k-points for generation (the number
you type<br>
in to kgen, not the number in the IBZ) then you'll need approx. 500
generating<br>
k-points for a 2x2x1 supercell. However the actuall number in the IBZ may
not<br>
be lower than the original because your symmetry is also lower<br>
<br>
</blockquote>In addition to what Georg wrote, you can find an equally
dense mesh also in the following way:<br><br>
For your original cell and original k-mesh, look at the top of
case.klist. It looks for instance like<br><br>
1
7 11 7 154 8.0 -7.0
1.5 1000 k, div: ( 11 7 11)<br>
2
7 11 21 154 8.0<br>
3
7 11 35 154 8.0<br><br>
Here you see (after the 'div') that your k-mesh is a 11x7x11 grid. If you
now double the unit cell in the x-direction (2x1x1), you Brillouin zone
will get half as large in that direction. This means you need half as
many gridpoints for k in that direction. Vary the input for kgen until
you see approximately 5x7x11 or 6x7x11. For a 2x1x2 supercell, you go for
5x7x5 or 6x7x6, for a 2x2x2 supercell you need 5x3x5 or 6x4x6,
etc.<br><br>
Stefaan</blockquote>
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Dr Ong Phuong Khuong <br>
Materials and Industrial Chemistry Department <br>
Institute of High Performance Computing <br>
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