Name

calculateElectronDensity Calculates the real-space electron density.

Synopsis

Namespace: ATK.KohnSham or ATK.TwoProbe
ElectronDensity calculateElectronDensity(self_consistent_calculation)

Description

Function that calculates and returns the self-consistent real-space electron density.

List of arguments

self_consistent_calculation

An object returned from a previously performed self-consistent calculation.

Default: None

Returned object methods

The returned object from calculateElectronDensity() has the following two query methods:

  • Array toArray(): Returns the real-space representation of the electron density in a NumPy array with dimension (n1,n2,n3) for a spin-unpolarized calculation and (2,n1,n2,n3) for a spin-polarized calculation where the spin-up components are the first entry.

  • PhysicalUnit toUnit(): Returns the unit of the electron density.

Usage examples

from ATK.KohnSham import *

atomic_configuration = ...
self_consistent_calculation = KohnShamMethod().apply(atomic_configuration)
electron_density = calculateElectronDensity(self_consistent_calculation)

f.addToSample(configuration,"My sample")
f.addToSample(electron_density,"My sample")

Notes

By default ATK uses (norm-conserving) pseudo-potentials for all supported elements. Therefore, the electron density calculated by calculateElectronDensity() is the one which includes only the valence electrons.

As shown in the example above, the returned object from this function can be placed in a VNL file, which may then be visualized in the Nanoscope in Virtual NanoLab.

The dimension of the returned array is (2,n_1,n_2,n_3) for spin-polarized calculations and (n_1,n_2,n_3) otherwise. The size of the array, i.e. the numbers n_i (i=1,2,3) depends on the mesh cut-off. The shape of the array can be obtained using the shape property, for example in order to perform calculations using the raw data:

electron_density = calculateElectronDensity(self_consistent_calculation)
electron_density_array = electron_density.toArray()
unit = electron_density.toUnit()
array_shape = electron_density_array.shape
print array_shape
(2,100,124,226)  # example output

The output example refers to a spin-polarized calculation, where the leading dimension thus is 2. Note that shape is a property (i.e. there are no parentheses), and not a method like toUnit()!