Exploring Density of States (DOS) and Band Structure

 

Calculation

In order to visualize the band structure in p4vasp, you will need to perform a corresponding calculation with VASP. There are several details that need to be considered:

  • Use relaxed geometry.
  • Precalculate the charge density.
  • Inspect DOS with full k-points mesh.
  • Inspect band structure with selected strips of k-points.
  • Consider the right method for projecting wave functions if you want projected DOS and band structure.

Please consult VASP manual for more details, especially section Accurate DOS and Band-structure calculations.

Example for this article can be found in Download/Examples: vasprun_ldos.xml.

Loading and 3D View

 

 

Visulaization will be explained on a PbTiO3 system. The vasprun.xml file you can download here.
Start p4vasp and open the file (select Open in toolbox or File/Load system from menu).
After the file is opened, you should see PbTiO3 in the System selection in the upper part of the p4vasp window.
You can show the 3d structure by pressing Show and adjust the view in Control.

DOS and Band structure

Select DOS+bands from the toolbar (or alternatively from menu Electronic/DOS + bands):


This will open a graph showing the density of states (DOS):


Waring about DOS: DOS is calculated from the k-points specified. DOS stemming from a strip of k-points will highly probable look differently from a DOS from a complete k-point mesh. Thus if you want to show DOS and band-structure, you will likely need to combine two different calculations.

In all DOS/bandstructure graphs is the energy relative to the Fermi energy - i.e. the Fermi energy on the graph is zero.

You can change between different modes (DOS / bandstructure) in graph menu Show:

  • show DOS turns showing DOS on and off. This is mainly useful for projected DOS.
  • DOS: Shows the density of states. (Energy on x-axis, DOS on y-axis.
  • DOS (X-axis): Shows the density of states. (Axes are switched, i.e. DOS on x-axis, energy on y-axis).
  • Bands: Shows the band structure.
  • DOS and Bands: Shows DOS and band structure side by side.

 

Local DOS and band structure

Calculation of local projections of DOS and band structure depends on VASP settings. Please consult the VASP manual.
Selecting Electronic/Local DOS+bands control from the menu will open a form, where you can add projected DOS and band structure to the graph:


This form controls display of both projected DOS and projected band structutre. It allows to select and sum up projections on different atoms, orbitals and spin projections.
In order to add a new projection do the following:

  1. Selecting atoms(s). You can do this by either pointing to atoms in 3d view and pressing space or by a selection language - e.g. "Pb" will select all lead atoms. Contributions on all selected atoms will be summed together.
  2. (optional) Write description label, that will appear in the graph legend. If not specified, it will be filled automatically.
  3. (optional) You can specify symbol color, type and size to be used for projected band structure.
  4. Spin projection (only relevant if spin has been calculated).
  5. Orbital projection: use checkboxes, select and deselect buttons to select desired spherical harmonics projections (orbitals). Press Select all to sum up all orbital projections. Contributions on all selected spherical harmonics projections will be summed together.
  6. Press Add new line.

Note, that graph will show DOS and/or band structure depending on what was selected in Show menu.