Keywords

SPECTRAL_TASK - determines what will be calculated. All tasks will compute the eigenenergies (aka bands). The list of tasks, and the extra properties calculated are as follows:

  • bandstructure
  • dos band gradients
  • optics optical matrix elements
  • pdos atomic projections
  • coreloss dipole matrix elements with core states

Most spectral calculations will involve the calculation of unoccupied states. One of the following parameters should be set to determine the number of states calculated.

SPECTRAL_NEXTRA_BANDS            number of extra spectral bands
SPECTRAL_PERC_EXTRA_BANDS        percentage of extra spectral bands
SPECTRAL_NBANDS                  number of bands/k-point in spectral calc

It is possible to use a different exchange-correlation functional to the one used for the groundstate. An example might be when a semi-local functional (such as PBE) is used for the groundstate, and a more expensive non-local functional (e.g. PBE0) is used for the spectral calculation. This is an approximation and should be done with cuation. To set the xc functional use one of the two keywords.

SPECTRAL_XC_FUNCTIONAL           spectral exchange-correlation functional
SPECTRAL_XC_DEFINITION           spectral exchange-correlation functional

To change the convergence tolerance for the eigenvalues set 

SPECTRAL_EIGENVALUE_TOL          ! default: 10E-6 eV

SPECTRAL_MAX_ITER maximum iterations in spectral calculation SPECTRAL_MAX_STEPS_PER_ITER maximum steps per iter in spectral calculation