# 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