k-point set setup

Creation of k-point sets

While you can use the documentation provided here to generate you own -point. It is usually recommended and much simpler to use input generator for this task.

In the FLEUR inp.xml file you typically find a series of XML-tags like this the cell section:

<bzIntegration valenceElectrons="20.00000000" mode="hist" fermiSmearingEnergy=".00100000">
   <kPointListSelection listName="default-1"/>
   <kPointLists>
      <kPointList name="default-1" count="2" nx="2" ny="2" nz="2" type="mesh">
         <kPoint weight="   2.00">  1.00/4.00   1.00/4.00   1.00/4.00</kPoint>
         <kPoint weight="   6.00">  1.00/4.00   2.00/4.00   2.00/4.00</kPoint>
      </kPointList>
   </kPointLists>
</bzIntegration>

Alternatively, the kPointLists might be put into a separate kpts.xml file and in the inp.xml you find the corresponding include.

<bzIntegration valenceElectrons="20.00000000" mode="hist" fermiSmearingEnergy=".00100000">
   <kPointlistselection Listname="default-1" />
   <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="kpts.xml">
</bzIntegration>

Brillouin zone integration

The highest level tag to be found is the bzIntegration tag:

Attribute Desciption
valenceElectrons The total number of valence electrons in your system
mode Method to determine the Fermi level. Supported are:
hist - Use the histogram mode. This is the default.
gauss - Use Gaussian smearing.
tria - Use the tetrahedron method.
fermiSmearingEnergy The Fermi smearing can be parametrized by this energy in Hartree.
fermiSmearingTemp As an alternative to fermiSmearingEnergy a Fermi smearing temperature can be set in Kelvin.

Selecting a k-point set

Then, the Kpointlistselection tag with a single attribute Listname is used to select the k-point set from the List provided. The Listname has to correspond to a Name attribute of one of the KpointLists.

The List of k-points

You might have different k-point sets in your setup, these KpointList XML elements are included into an outer KpointLists tag. Usually, the inpgen will generate multiple sets of k-points initially. With further calls to inpgen you might create further sets.

A Kpointlist is defined with the following attributes:

Attribute Desciption
Name Name of the k-point set to be used in Kpointlistselection. (required)
Count Number of k-points in the set. (optional)
type Description of the type: at present one of mesh,path,tria-bulk,tria,SPEX-mesh,unspecified (optional)
nx,ny,nz Size of the mesh in three spatial directions. (optional)
nkq_pairs Pairs of k,q vectors in a hybrid calculation. (optional)

Each kPoint element features the attribute weight and three numbers. The weight is the weight of the point in the Brillouin zone integration. Each of the three numbers is divided by the value of the posScale attribute of the kPointList element to obtain the coordinates of the point. In addition a label can be provided for use in bandstructure calculations.