Grid denisty

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Jamoliddin
Posts: 4
Joined: Sat Nov 14, 2020 7:50 am

Grid denisty

Post by Jamoliddin » Mon Dec 07, 2020 7:47 am

Hello,

Is there anyway to set the grid (mesh) density in the input file?

Thank you.

fgygi
Site Admin
Posts: 140
Joined: Tue Jun 17, 2008 7:03 pm

Re: Grid denisty

Post by fgygi » Mon Dec 07, 2020 9:09 pm

The size of the grid used to represent the charge density in real space is determined by the value of the plane wave energy cutoff ecut and the size of the unit cell cell. The size can be printed using the status command after setting the values of cell and ecut:

Code: Select all

[qbox] set cell 20 0 0  0 20 0  0 0 20
<unit_cell 
    a="20.00000000  0.00000000   0.00000000  "
    b="0.00000000   20.00000000  0.00000000  "
    c="0.00000000   0.00000000   20.00000000 " />
[qbox] set ecut 60
[qbox] status
<np0v> 112 </np0v>  <np1v> 112 </np1v>  <np2v> 112 </np2v>
<wf ecut="30.00000000" nspin="1" nel="0" nempty="0">
<cell a="20.000000 0.000000 0.000000"
      b="0.000000 20.000000 0.000000"
      c="0.000000 0.000000 20.000000"/>
 reciprocal lattice vectors
 0.314159 0.000000 0.000000
 0.000000 0.314159 0.000000
 0.000000 0.000000 0.314159
<refcell a="0.000000 0.000000 0.000000"
         b="0.000000 0.000000 0.000000"
         c="0.000000 0.000000 0.000000"/>
<grid nx="56" ny="56" nz="56"/>
<slater_determinant kpoint="0 0 0" size="0">
 sdcontext: 1x1
 basis size: 31335
 c dimensions: 31335x0   (31335x1 blocks)
 <density_matrix form="diagonal" size="0"/>
</slater_determinant>
</wf>
<vcm> 0.000000 0.000000 0.000000 </vcm>
In this example, the charge density grid is 112x112x112 (elements <np0v> etc.), and the wave function grid is 56x56x56 (element <grid>).

Jamoliddin
Posts: 4
Joined: Sat Nov 14, 2020 7:50 am

Re: Grid denisty

Post by Jamoliddin » Tue Dec 08, 2020 9:44 am

Thank you for reply.
But can we modify the grid dimension keeping 'ecut' and 'cell' unchanged.
Best.

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