# Density of States (DOS)¶

DOS
CalcDOS Yes/No
CalcPDOS Yes/No
CalcPopulationAnalysis Yes/No
DeltaE float
Energies integer
File string
IntegrateDeltaE Yes/No
Max float
Min float
StoreCoopPerBasPair Yes/No
End

DOS
Type: Block Density-Of-States (DOS) options
CalcDOS
Type: Bool Yes Calculate DOS Whether or not to calculate the density of states.
CalcPDOS
Type: Bool No Calculate PDOS Whether or not to calculate the partial DOS (projections on basis functions). This can be significantly more expensive than calculating the total DOS
CalcPopulationAnalysis
Type: Bool Yes Calculate Mulliken charges Whether or not to calculate the population analysis. Population analysis can become very expensive when there are many symmetry operators, such as in a super cell.
DeltaE
Type: Float 0.005 Hartree Energy step for the DOS grid. Using a smaller value (e.g. half the default value) will result in a finer sampling of the DOS.
Energies
Type: Integer Number of equidistant energy-values for the DOS grid. This keyword supersedes the ‘DeltaE’ keyword.
File
Type: String Write the DOS (plain text format) to the specified file instead of writing it to the standard output.
IntegrateDeltaE
Type: Bool Yes This subkey handles which algorithm is used to calculate the data-points in the plotted DOS. If 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)]. If 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.
Max
Type: Float Hartree User defined upper bound energy (with respect to the Fermi energy)
Min
Type: Float Hartree User defined lower bound energy (with respect to the Fermi energy)
StoreCoopPerBasPair
Type: Bool No Calculate COOP Calculate the COOP (crystal orbital overlap population).

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).

Tip

The tutorial Calculation of Band Structure and COOP of CsPbBr3 with BAND contains some advanced usage of the DOS and BAND Structure GUI modules.

## Gross populations¶

GrossPopulations # Non-standard block. See details.
...
End

GrossPopulations
Type: Non-standard block Partial DOS (pDOS) are generated for the gross populations listed under this key. See example.

Syntax:

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 # Non-standard block. See details.
...
End

OverlapPopulations
Type: Non-standard block Overlap population weighted DOS (OPWDOS), also known as the crystal orbital overlap population (COOP).

Overlap population weighted DOS 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