[Pw_forum] problems of the K points of the unit cell and supercell

[Chengyang Li]

Thanks a lot. I will try it. 

Chengyang 

----- Original Message -----

> From: "Yun Wang" <yun.wang at griffith.edu.au>
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Sent: Wednesday, April 24, 2013 3:17:38 PM
> Subject: Re: [Pw_forum] problems of the K points of the unit cell and
> supercell

> Hi Chengyang,

> You can run a series of calculations with different k-point meshes.
> The right k-point mesh density can be determined once the total
> energies converge.

> Cheers,
> Yun

> On Thu, Apr 25, 2013 at 5:18 AM, Chengyang Li <
> li.chengyang at wmich.edu > wrote:

> > Dear all
> 

> > I have a question about the K points. When I try to repeat the unit
> > cell to get a supercell. I found someone said if the structure is
> > changed, the K points should be changed at the same time if we want
> > to keep the same result. I try to calculate the phonon of the
> > chromium, the atomic positions and cell parameters are like this:
> 

> > Unit cell
> 

> > ATOMIC_POSITIONS crystal
> 
> > Cr1 0.000000000 0.000000000 0.000000000
> 

> > CELL_PARAMETERS cubic
> 
> > 0.500000000 0.500000000 0.500000000
> 
> > -0.500000000 0.500000000 0.500000000
> 
> > -0.500000000 -0.500000000 0.500000000
> 

> > Supercell, there are two unit cells in this cell.
> 

> > ATOMIC_POSITIONS crystal
> 
> > Cr1 0.000000000 0.000000000 0.000000000
> 
> > Cr1 0.000000000 0.000000000 0.500000000
> 
> > Cr1 0.500000000 0.500000000 0.250000000
> 
> > Cr1 0.500000000 0.500000000 0.750000000
> 

> > CELL_PARAMETERS
> 
> > 1.000000000 0.000000000 0.000000000
> 
> > 0.000000000 1.000000000 0.000000000
> 
> > 0.000000000 0.000000000 2.000000000
> 

> > If I set the unit cell like this
> 

> > K_POINTS automatic
> 
> > 4 4 4 1 1 1
> 

> > How should I change the k points in the supercell?
> 

> > Thank you for the attention.
> 

> > Chengyang Li
> 

> > Western Michigan University,
> 

> > _______________________________________________
> 
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> 
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> 
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> 

> --

> Dr. Yun Wang
> Research Fellow
> Centre for Clean Environment and Energy
> Griffith School of Environment
> Gold Coast Campus, Griffith University
> QLD 4222, Australia
> Tel:(61-7) 5552 8456
> Fax:(61-7) 5552 8067
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