Additional periodicity data

Periodic
   KSpace integer
   EffectiveMass
      Enabled [True | False]
      KPointCoord float_list
      NumAbove integer
      NumBelow integer
      StepSize float
   End
   BandStructure
      Automatic [True | False]
      DeltaK float
      Enabled [True | False]
      FatBands [True | False]
      UseSymmetry [True | False]
   End
   BZPath
      Path # Non-standard block. See details.
         ...
      End
   End
   DOS
      EMax float
      EMin float
      NSteps integer
   End
   Screening
      dMadel float
      rMadel float
   End
End
Periodic
Type:Block
Description:Block that sets various details of the calculation only relevant for periodic systems.
KSpace
Type:Integer
Default value:1
Description:This parameter controls the number of k-points used in the calculation. By default DFTB does not do any k-space sampling and uses only the Gamma-point as the only k-point. This should be sufficient for systems with large unit cells For smaller systems, k-space sampling can be enabled explicitly using this keyword. For very small unit cells (one atom wide) a value of 5 is advised. For medium sized unit cells 3 is adequate. The k-space sampling is relatively new in DFTB and as of the ADF2017 release still has some incompatibilities with other features: At the moment it is not possible to use k-space sampling in combination with DFTB3, spin-polarization, l-dependent SCC cycles or density matrix purification. Furthermore, if KSpace is not 1 (Gamma-only in GUI) DFTB can only run in serial mode. If not running via the GUI you need to do this yourself (use NSCM=1).
EffectiveMass
Type:Block
Description:In a semi-conductor, the mobility of electrons and holes is related to the curvature of the bands at the top of the valence band and the bottom of the conduction band. With the effective mass option, this curvature is obtained by numerical differentiation. The estimation is done with the specified step size, and twice the specified step size, and both results are printed to give a hint on the accuracy. By far the most convenient way to use this key is without specifying any options.
Enabled
Type:Bool
Default value:False
Description:In a semi-conductor, the mobility of electrons and holes is related to the curvature of the bands at the top of the valence band and the bottom of the conduction band. With the effective mass option, this curvature is obtained by numerical differentiation. The estimation is done with the specified step size, and twice the specified step size, and both results are printed to give a hint on the accuracy. By far the most convenient way to use this key is without specifying any options.
KPointCoord
Type:Float List
Unit:1/Bohr
Recurring:True
Description:Coordinate of the k-points for which you would like to compute the effective mass.
NumAbove
Type:Integer
Default value:1
Description:Number of bands to take into account above the Fermi level.
NumBelow
Type:Integer
Default value:1
Description:Number of bands to take into account below the Fermi level.
StepSize
Type:Float
Default value:0.001
Description:Size of the step taken in reciprocal space to perform the numerical differentiation
BandStructure
Type:Block
Description:Options for band structure plotting. This has no effect on the calculated energy. [Warning: The band structure is only computed in case of k-space sampling, i.e. it is not computed for Gamma-only calculations (see: Periodic%KSpace).]
Automatic
Type:Bool
Default value:True
Description:Generate and use the standard path through the Brillouin zone. If not, use the user defined path (set via Custom path in the GUI, or with the Periodic%BZPath keyword in the run script).
DeltaK
Type:Float
Default value:0.1
Unit:1/Bohr
Description:Step size in reciprocal space for band structure interpolation. Using a smaller number will produce smoother band curves at an increased computational time.
Enabled
Type:Bool
Default value:True
Description:Whether or not to calculate the band structure.
FatBands
Type:Bool
Default value:True
Description:Control the computation of the fat bands (only when the bandstructure is calculated). The fat bands are the periodic equivalent of the Mulliken population analysis. The definition of the fat bands can be found in the Band Documentation.
UseSymmetry
Type:Bool
Default value:True
Description:If set, only the irreducible wedge of the Wigner-Seitz cell is sampled. If not, the whole (inversion-unique) Wigner-Seitz cell is sampled.
BZPath
Type:Block
Description:If [BandStructure%Automatic] is disabled, DFTB will compute the band structure for the user-defined path in the [BZPath] block. You should define the vertices of your path in fractional coordinates (with respect to the reciprocal lattice vectors) in the [Path] sub-block. If you want to make a jump in your path, you need to specify a new [Path] sub-block.
Path
Type:Non-standard block
Recurring:True
Description:A section of a k space path.
DOS
Type:Block
Description:The subkeys of [DOS] allow to customize the calculation of the density of states.
EMax
Type:Float
Default value:0.75
Unit:Hartree
Description:Upper end of the energy interval in which the density of states is calculated.
EMin
Type:Float
Default value:-0.75
Unit:Hartree
Description:Lower end of the energy interval in which the density of states is calculated.
NSteps
Type:Integer
Default value:300
Description:The number of energy intervals between [EMin] and [EMax] for which the density of states is calculated.
Screening
Type:Block
Description:For SCC-DFTB in periodic systems the Coulomb interaction is screened with a Fermi-Dirac like function defined as TODO S(r)=1/(exp((r-r_madel)/d_madel)+1). Screening is always enable, even if this section is absent. This section allows to change some details of the screening procedure.
dMadel
Type:Float
Unit:Bohr
Description:Sets the smoothness of the screening function. The default is 1/10 of [rMadel].
rMadel
Type:Float
Unit:Bohr
Description:Sets the range of the screening function. The default is 2x the norm of the longest lattice vector.