The different DOS and bandstructure modes of FLEUR
Fleur supports the calculation of several "DOS-like" quantities which can be understood to be obtained in a two-step procedure.
- For each of the eigenstates a set of "weights" is obtained.
- These weights are then used in a k-integration.
From this general structure one can already conclude that there are two different possible output quantities that could be of interest. On the one hand
the weight as a function of k-vector, band-index and possibly spin and on the other hand the integrated weight as a function of energy and spin. The first of these can be used to further describe the eigenspectrum in a "bandstructure" view, while the second is a "DOS"-like quantity.
<output band="T"> in the
inp.xml Fleur will output these weights for each state, while the
<output dos="T"> switch will trigger the k-integration to write out the integrated weights. Hence, the modes as described below can be used with setting the
dos switch in the
The different weights supported by Fleur include the local, -resolved density, the orbital decomposed charges, vacuum charges and the MCD matrix elements. Details are described below.
Common input switches and resulting output
The most basic setings for generating a DOS-like quantity are then specified in the
output/bandDOS tag. For example:
<output dos="T"> <banddos minEnergy="-0.5" maxEnergy="0.5" sigma="0.01" numberPoints="1321" /> </output>
banddos tag must be used to specify the most basic quantities controlling the DOS k-point integration.
|minEnergy| minimal energy of the DOS grid in Hartree (default=-0.5)
|maxEnergy| maximal energy of the DOS grid in Hartree (default=0.5)
|sigma| smearing energy to smoothen the DOS in Hartree (default=0.01)
|numberPoints| point between minEnergy and maxEnergy (default=1321)
Local and -resolved charges
By default Fleur calculates weights by considering the local -resolved charges in the muffin-tin spheres due to the states. Here we calculate for each atom the charge expanded in spherical harmonics, i.e. the contributions of the l=0, l=1, l=2, and l=3 or s,p,d,f-like charges. The corresponding weights will be labeled by a string like "MT:5d" for the d-like charge of the 5th atom type.
A label like
MT:6s is to be understood as the s-like charge of the 6th atom type. Not as a charge of 6s-states.
In addition, the default mode also creates three additional weight "Total", "INT" and "Sym". While the "Total" weight is simply "1.0" for all states, the "INT" weight contains the local DOS in the Interstitial region. The "Sym" weight contains a integer value indicating which representation of the local symmetry corresponding to the k-point the state belongs to.
The data generated in this mode are written to the files "Local.1/2" and/or to the corresponding groups in the banddos.hdf file.
Orbital decomposed charges
In addition to the simple projection onto s,p,d,f orbital, you can also generate more detailed information projecting onto the different (real) spherical harmonics. This mode is switched on by setting the attribute
orbcomp="T" in the
banddos tag. So a minimal input setting in the output section would be:
<output dos="T"> <banddos orbcomp="T" /> </output>
This will give you weights like
ORB:1ind:3. Here again the first number after the
ORB: will indicate the atom considered.
Counting of atoms in ORB-mode
As the orbital decomposition is calculated for each atom not only once for each atom-type be sure you analyse the correct atom. Use the List of atoms in the output to verify which atom you are looking at.
The second number in the label of the weight, i.e. the number after the
ind:, is an index counting though the orbitals as follows:
1:s-state, 2-4: p-states, 5-9: d-states, 10-16: f-states(cubic), 17-23: f-states(low symmetry).
The data generated in this mode are written to the "Orbcomp" group in the banddos.hdf file.
For film-setups, i.e. if Fleur is using an input for a film, one can write out various projections of the states in the vacuum. The correspond section in the
inp.xml file is:
<output dos="T"> <vacuumDOS vacdos="T" integ="F" star="F" nstars="1" locx1="0.0" locy1="0.0" locx2="1.0" locy2="1.0" nstm="0" tworkf="0.0> <layer> 10 </layer> </vacuumDOS> </output>
|vacdos||switch on/off the evaluation of vacuum charges (required)|
|integ||switch to activate a z-integration between the layers specified (default="F")|
|stars||switch to activate a decomposition according to 2D stars (default="F")|
|nstars||number of stars to use in decomposition (must be given if stars="T")|
|locx/y/1/2||definition of a 2D area in which to integrate the DOS (optional)|
|nstm||switch for different simulation modes for an STM tip (expert usage)|
|tworkf||work function of the tip in STM mode (expert usage)|
|layer||layer at which the DOS should be evaluated. Several layers can be given.|
The layers are specified on the internal z-grid Fleur is using in the vacuum. By default we use 100 points with a spacing of 0.1 a.u. So layer should be a number between 1 and 100.
The weights generated by this mode are specified by the following labels: |label|description |----|---- |VAC1| total weight in the first vacuum |VAC2| total weight in the second vacuum |Layer1-x| weight (2D) integrated on the layer x (first vacuum) |Layer2-x| weight (2D) integrated on the Layer x (second vacuum) |R(gVAC1)-x-y| Real part of weight for star y on layer x (first vacuum) |I(gVAC1)-x-y| Imaginary part of weight for star y on layer x (first vacuum) |R(gVAC2)-x-y| Real part of weight for star y on layer x (second vacuum) |I(gVAC2)-x-y| Imaginary part of weight for star y on layer x (second vacuum)
The data generated in this mode are written to the "Vacuum" group in the banddos.hdf file.
MCD matrix elements
To evaluate MCD matrix elements the following tags can be set:
<output dos="T"> <magneticCircularDichroism mcd="T" energyLO="-2.0" energyUp="-1.0" /> </output>
Besides switching on the mode using the
mcd attribute, you also have to specify the energy window for the selection of the core-states.
This mode generates weight labels by a string like "At1NC2pos", where again the first number after the "At" labels the atom type considered, the number after "NC" iterates through the core-states used and the description ends in "pos","neg","cir" for the positive, negative and circular contributions.
The data generated in this mode is written to the "MCD" group in the banddos.hdf file.
Selection of atoms for the DOS/Bandstructure output
As some of the modes can lead to a large amount of data being generated, the application of the switches can be restricted to a subset of atoms only. For this two different switches are implemented:
- In the
all_atomsattribute can be specified. It defaults to "T" but can be used to switch off the generation of weights for all atoms.
<output dos="T"> <bandDOS all_atoms="F" /> </output>
- For each atomic position, a
banddosattribute can be given to switch on/off the generation of weights:
<relpos label="something" banddos="F"> 0.0 0.0 0.0 </relpos>
In addition, one can use the
gamma attributes to rotate the coordinate frame of the atom and thus change the assignment of the orbital decomposed weights.
<relpos label="something" alpha="0.0" beta="0.0" gamma="Pi"> 0.0 0.0 0.0 </relpos>