The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <xavier.gonze@uclouvain.be>]

Dear Rob,

The tutorial example 3.1 example needs indeed more explanation,
to meet your concerns. This will be corrected (well sooner or  
later ...).

From a practical point of view, there is an automatic technique
in ABINIT to generate good sets of k points, using the input variable  
prtkpt. See the examples in
tests/v2, tests 61 to 73 .

Best wishes,
Xavier

On 18 Jun 2009, at 13:11, Rob wrote:

> matthieu verstraete wrote:
> > In your specific case, it looks like you generate the same grid with
> > your 4 shifts as with the default, which is 1 shift of 1/2 1/2 1/2.
> > This is somewhat of a coincidence, and with a less cubic system will
> > not happen. Try with nshift 1 shiftk 0 0 0 and you will see a
> > difference in the energy.
>
> Well, it's not "my specific case", but it's the Tutorial 3.1 example  
> from ABINIT !
> This example is designed to show the use of nshift and shiftk.
>
> Then obviously this Tutorial 3.1 example is not a good example as it  
> does
> not demonstrate the necessity for the use of nshift and shiftk.
>
> With nshift 1 shiftk 0 0 0, the total energy in Tutorial 3.1 goes up  
> a bit.
>
> Rob.
>
> Here is the current input file t31.in of Tutorial 3.1:
> acell 3*10.18
> rprim  0.0  0.5  0.5
>       0.5  0.0  0.5
>       0.5  0.5  0.0
> ntypat 1
> znucl 14
> natom 2
> typat 1 1
> xred
>   0.0  0.0  0.0
>   1/4  1/4  1/4
> ecut  8.0
> kptopt 1
> ngkpt 2 2 2
> nshiftk 4
> shiftk 0.5 0.5 0.5
>       0.5 0.0 0.0
>       0.0 0.5 0.0
>       0.0 0.0 0.5
> nstep 10
> toldfe 1.0d-6
> diemac 12.0