[Wien] bcc case.klist

[Peter Blaha]

"number of k-points" and "divisions" are usually the same thing anyway.

As I said before, the k-points are generated in the primitive (rhombohedral)
cell. In this frame they are "continuous" and the outputkgen file gives you
even the relation between them.

In the carthesian frame (this is used in case.klist) they are distributed somewhere
(maybe outside the 1st BZ). When you apply a symmetry operation and then
try to bring the k-point back, remember that a vector (1,0,0)*2pi/a is NOT a
reciprocal lattice vector for F and B centered lattices!


Elisabeth Magerl schrieb:
> Dear users,
> 
> I still have troubles with my klist file. I have tried to generate my own
> list, using divisors for kgen instead of a number of kpoints, and get
> again a mesh where the points partly lie outside the first Brillouin zone
> and do not form a single block. I also tried to apply the symmetry
> operations of my bcc lattice to the points in klist, but I still end up
> with areas which are not sampled.
> Is there any way to find out how the mesh is generated and how my kpoints
> outside the first zone can be represented inside it? I have to get a
> continuous k-mesh, otherwise I cannot apply a gradient to my eigenvalues.
> I browsed the mailing list and the user manual, but I could not find a
> solution to my problem.
> 
> Thank you for your help,
> Elisabeth
> 
> 
> Elisabeth Magerl schrieb:
> Dear professor Blaha,
> 
> thank you for your answer. I am sorry I asked something which seems to be
> already discussed, unfortunately I was not able to find it in the previous
> posts.
> Maybe the term 'energy surface' was misleading. I am calculating group
> velocities from the bandstructure, so I have to know which k-points lie
> next to each other to get the curvature right. My idea was to take the
> eigenvalues in case.energy, relate them to the kpoints in case.klist and
> calculate the gradient.
> I used xcrysden to get a distribution of k-points along symmetry lines,
> but now I would like to sample the whole Brillouin zone.
> 
> Thank you,
> Elisabeth
> 
> 
> Peter Blaha pblaha at theochem.tuwien.ac.at wrote:
> 
> As mentioned before, for centered lattices the k-mesh is generated in the
> "primitive cell", symmetry is applied to reduce this mesh, and than it is
> transfered into carthesian coordinates. In this step, it happens that some
> k-points are given outside the first BZ. This does not influence any
> results.
> 
>   > interested in the shape of the energy surface,
> 
> You mean the fermi surface ??
> Consider xcrysden for 3d-plots or the fsgen program for 2d cuts.
> 
> 
> 
> Elisabeth Magerl schrieb:
>> Dear Wien2k users,
>>
>> I have a problem with understanding the klist-file I get out for a bcc
>> structure. I set up a case for a normal 3d tungsten structure, the
>> results for the bandstructure are in good agreement with published data
>> - so everything works properly.
>>
>> If I now look at the distribution of the k-points in my initial
>> klist-file, I find that they do not resemble the irreducible wedge but
>> are buidling up two isolated blocks (I attached a list of the k-points
>> and a plot showing the distribution mapped on the xy-plane). It seems
>> that the second block is lying outside the first Brillouin zone. Do I
>> have to apply a symmetry operation to get it in the right place? I am
>> interested in the shape of the energy surface, so I have to get the
>> k-points related to each other correctly.
>>
>> Thank you in advance,
>> Elisabeth
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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