[Wien] Supercell

[Khuong P. Ong]

Dear Dr. Stefaan and Georg,

  It is definitely very interesting for me to know about this. I deeply 
thank you for your help.

  Have a nice day.

Regards,
Khuong


At 04:55 PM 6/14/2005, you wrote:
>>I'm no expert on these supercell calculations, but I guess the density of
>>k-points should be the same.
>>This means that if you you use 2000 k-points for generation (the number 
>>you type
>>in to kgen, not the number in the IBZ) then you'll need approx. 500 
>>generating
>>k-points for a 2x2x1 supercell. However the actuall number in the IBZ may not
>>be lower than the original because your symmetry is also lower
>>
>In addition to what Georg wrote, you can find an equally dense mesh also 
>in the following way:
>
>For your original cell and original k-mesh, look at the top of case.klist. 
>It looks for instance like
>
>         1    7   11    7  154  8.0 -7.0  1.5      1000 k, div: ( 11  7 11)
>         2    7   11   21  154  8.0
>         3    7   11   35  154  8.0
>
>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.
>
>Stefaan

*******************************************************
Dr Ong Phuong Khuong
Materials and Industrial Chemistry Department
Institute of High Performance Computing
1 Science Park Road
#01-01 The Capricorn
Singapore Science Park II
Sinagpore 117528
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