LocalDeviceDensityOfStates

	LocalDeviceDensityOfStates
DeviceDensityOfStates	MakeTrajectory

Name

LocalDeviceDensityOfStates — Class for representing the Local Device Density of States for a given configuration and calculator.

Synopsis

Namespace: NanoLanguage

LocalDeviceDensityOfStates(
configuration,
energy,
kpoints,
contributions,
self_energy_calculator,
energy_zero_parameter,
infinitesimal,
spin
)

Description

Constructor for the Local Device Density of States class.

LocalDeviceDensityOfStates Arguments

configuration

The two-probe configuration with attached calculator for which the LDDOS should be calculated.

Type: DeviceConfiguration

Default:


          None

energy

The energy for which the LDDOS should be calculated.

Type: A PhysicalQuantity with energy unit.

Default:


          0.0*eV

kpoints

The k-points for which the LDDOS should be calculated.

Type: MonkhorstPackGrid

Default:


          MonkhorstPackGrid(nx,ny), where nx, ny is the sampling used for the self consistent calculation.

contributions

The density contributions to include in the LDDOS.

Type: Left | Right | All

Default:

All

self_energy_calculator

The self energy calculator to use.

Type: DirectSelfEnergy | RecursionSelfEnergy | KrylovSelfEnergy

Default:


          KrylovSelfEnergy

energy_zero_parameter

Specifies the choice for the energy zero.

Type: AverageFermiLevel | AbsoluteEnergy

Default:


          AverageFermiLevel

infinitesimal

Small energy, used to move the LDDOS calculation away from the real axis. This is only relevant for recursion-style self-energy calculators.

Type: PhysicalQuantity with eV units.

Default:


          1.0e-6*eV

spin

The spin for which the LDDOS should be calculated.

Type: Spin.Sum | Spin.Up | Spin.Down.

Default:


          Spin.Sum

LocalDeviceDensityOfStates Methods

A LocalDeviceDensityOfStates object provides the following methods:

contributions(): Query function for the contributions parameter.
derivatives(x, y, z): Calculate the derivative in the point x,y,z.

x

The cartesian x coordinate.

Type: physical quantity with type length.

y

The cartesian y coordinate.

Type: physical quantity with type length.

z

The cartesian z coordinate.

Type: physical quantity with type length.
energy(): Query function for the energy parameter.
energyZero(): Query function for the energy zero value in absolute numbers.
energyZeroParameter(): Query function for the energy zero parameter.
evaluate(x, y, z): Evaluate in the point x,y,z

x

The cartesian x coordinate.

Type: physical quantity with type length.

y

The cartesian y coordinate.

Type: physical quantity with type length.

z

The cartesian z coordinate.

Type: physical quantity with type length.
gridCoordinate(i, j, k): Return the coordinate for a given grid index.

i

The grid index in the A direction.

Type: integer

j

The grid index in the B direction.

Type: integer

k

The grid index in the C direction.

Type: integer
nlprint(stream): Method for printing an ASCII table with the LDDOS.

stream

The stream the LDDOS should be written to.
Type: A stream that supports strings being written to using 'write'.
Default: sys.stdout
scale(scale): Scale the field with a double.

scale

The parameter to scale with.

Type: float
shape(): Query function for getting the shape of the data.
spin(): Query function for the spin parameter.
toArray(): Return the values of the grid as a numpy array slicing off any units.
unit(): Get the unit of the data in the grid.
unitCell(): Return the unit cell for the grid.
volumeElement(): Get the volume element of the grid.

Usage Examples

Calculate the local device density of states for a device configuration and save the result in a NetCDF for visualization with VNL.

ldos = LocalDeviceDensityOfStates(device_configuration, 0.0*eV,  contributions=All)
nlsave('ldos.nc',ldos)

For examples on how to average and handle 3-d grids, see the examples for ElectronDifferenceDensity and ElectrostaticDifferencePotential.

Notes

The local device density of states, $D(E, {\bf r})$ , shows the spectral density matrix, $D_{nm}(E)$ in real space

$\displaystyle D(E, {\bf r}) = \sum_{nm} D_{nm}(E) \phi_n( {\bf r}) \phi_m( {\bf r}) .$

The DeviceDensityOfStates is related to the LocalDeviceDensityOfStates through

$\displaystyle D(E) = \int D(E, {\bf r}) d {\bf r} = \sum_{nm} D_{nm}(E) S_{mn},$

where $S_{mn}$ is the overlap matrix.

The routine utilizes the symmetries of the configuration to reduce the computational load for k-point averages.