# calculateDensityMatrix¶

calculateDensityMatrix(configuration, kpoint=None, spin=None)

Calculate the the Fourier component of the Density Matrix.

Parameters: configuration (MoleculeConfiguration | BulkConfiguration | DeviceConfiguration | SurfaceConfiguration) – The configuration to use for the calculation. kpoint (tuple of floats) – The kpoint as three floats representing fractional reciprocal space coordinates. Default: The Gamma point (0.0, 0.0, 0.0) spin (Spin.Up | Spin.Down | Spin.All) – The spin component for which to perform the calculation. Default: Spin.All The density matrix. numpy.array

## Usage Examples¶

Evaluate the density matrix of a BulkConfiguration.

density_matrix = calculateDensityMatrix(bulk_configuration)


## Notes¶

• Extract the Fourier transformed density matrix of a BulkConfiguration.

$D({\bf k})_{\mu,\nu} = \sum_{n} f_n c^\dagger_\mu(n,{\bf k}) c_\nu(n,{\bf k}),$

where $$f_n$$ are Fermi occupation factors and $$c_\nu(n,{\bf k})$$ are basis function coefficients for eigenstate $$n, {\bf k}$$ , i.e

$H({\bf k}) {\bf c}(n, {\bf k}) = E_n S({\bf k}) {\bf c}(n, {\bf k})$
• The calculator assigned to the device must be density matrix-based for this function to perform successfully.

• Consider Note on Spin in low level interface functions for details on how to handle the spin parameter.