CH_LSPEC

CH_LSPEC = [logical]
Default: CH_LSPEC = .FALSE.

Description: This flag controls whether the imaginary part of the dielectric function for a selected core electron is calculated and written to the OUTCAR file or not.

How to calculate XAS spectra from core-hole calculations is explained here: SCH calculations.

This feature is only available from VASP version 6.0 or higher.

The broadening type of the spectrum is controlled by ISMEAR and the broadening in eV is set by CH_SIGMA. We recommend to use a very small Gaussian broadening ISMEAR=0 and CH_SIGMA $\le$ 0.001 in the calculations and broaden the spectrum in post processing. If another type of ISMEAR is required for the electronic calculation, one can run that in a first step and use the converged WAVECAR from that step together with ALGO=None and ISMEAR=0 in a second step to obtain the spectrum.

Warning: For XAS calculations it is strongly recommended to use the available GW PAW potentials for the POTCAR files, since many standard potentials don't have projectors with quantum numbers 2 or larger and the GW potentials are more exact for excited states than the standard potentials.

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