Density of States (DOS)¶

DOS (block-type)

General Density-Of-States (DOS) information.

DOS
   {Enabled [True|False]}
   {DeltaE value}
   {Energies n}
   {Min value}
   {Max value}
   {IntegrateDeltaE [True|False]}
   {File filename}
End

Enabled

(Default: False) Whether or not to calculate the density of states.

DeltaE

(Default: 0.005 a.u.) Energy step for DOS grid. Using a smaller value (e.g. 0.001) will result in a finer sampling of the DOS.

Energies

Number of equidistant energy-values. This keyword supersedes the DeltaE keyword.

Min

(Default: Energy of the lowest band) lower bound energy (w.r.t. Fermi level) in a.u.

Max

(Default: Fermi energy + 0.75 a.u.) upper bound energy (w.r.t. Fermi level) in a.u.

IntegrateDeltaE

(default=true) This subkey handles which algorithm is used to calculate the data-points in the plotted DOS.

IntegrateDeltaE true: the data-points represent an integral over the states in an energy interval. Here, the energy interval depends on the number of Energies and the user-defined upper and lower energy for the calculation of the DOS. The result has as unit [number of states / (energy interval * unit cell)].
IntegrateDeltaE false: the data-points do represent the number of states for a specific energy and the resulting plot is equal to the DOS per unit cell (unit: [1/energy]). Since the resulting plot can be a wild function and one might miss features of the DOS due to the step length between the energies, the default is set to the integration algorithm.

File

(Optional) handles the name of the output file with the DOS results.

An example input:

DOS
   Enabled     True
   Energies    500
   Min        -0.35
   Max         1.05
   File        plotfile
End

According to this example, DOS values will be generated in an equidistant mesh of 500 energy values, ranging from 0.35 a.u. below the Fermi level to 1.05 a.u. above it. All information will be written to a file plotfile. The information on the plot file is a long list of pairs of values (energy and DOS), with some informative text-headers and general information. DOS values are generated for the total DOS and optionally also for some partial DOS (see the keys GrossPopulations and OverlapPopulations).

In the DOS and Band Structure GUI modules, it is possible to visualize partial density of states (p-DOS). The partial contributions are obtained from the total DOS by following the Mulliken population analysis partitioning prescription (see wikipedia).

Gross populations¶

GrossPopulations (block-type)

Partial DOS (pDOS) are generated for the gross populations listed under this key.

GrossPopulations
   {iat lq}
   {FragFun jat ifun}
   {Frag kat}
   {Sum
    ...
    EndSum}
End

iat: pDOS is generated for atom lq.
FragFun: pDOS is generated for atom jat with all real spherical harmonics belonging to \(l\)-value ifun.
Frag: pDOS of the functions belonging to atom kat will be calculated.
Sum: sum all pDOS, specified in this block.

Example:

GrossPopulations
   FragFun 1 2:: Second function of first atom
   Frag 2 :: Sum of all functions from second atom
   SUM:: sum following PDOSes
      Frag 1::Atom nr.1
      FragFun 2 1::First function of second atom
      5 1:: All pfunctions of fifth atom
   EndSum
End

Overlap populations¶

OverlapPopulations (block-type)

Overlap population weighted DOS (OPWDOS), also known as the crystal orbital overlap population (COOP), are generated for the overlap populations listed

OVERLAPPOPULATIONS
   Left
      { iat lq }
      { FragFun jat ifun }
      { Frag kat }
   Right
      ...
End

You can use this to get the OPWDOS of two functions, or, if you like, one bunch of functions with another bunch of functions. The key-block should consist of left-right pairs. After a line with left you enter lines that specify one or more functions (according to GrossPopulations), followed by a similar structure beginning with right, which will produce the OPWDOS of the left functions with the right functions. Example:

OVERLAPPOPULATIONS
   LEFT::First OPWDOS
      Frag 1
   RIGHT
      Frag 2
   LEFT:: Next OPWDOS
      FragFun 1 1
   RIGHT
      2 1
      FragFun 3 5
End