Requesting core level spectroscopy

Calculating core level spectra produces electronic energies on the Monkhorst-Pack mesh of k-points and the matrix elements for electronic interband transitions. The CASTEP Analysis dialog can be used to generate observable core level spectra based on this information. Detailed analysis of the impact of calculation parameters (k-point set, number of empty bands, and so on) on the accuracy of the spectra generated can be found in the core level spectroscopy theory topic.

To calculate core level spectra

Choose Modules | CASTEP | Calculation from the menu bar.
Select the Properties tab.
Check the Core level spectroscopy option on the properties list.
If necessary, modify the number Energy range above the Fermi level for which you wish to calculate the spectrum.
Optionally, adjust the density of Monkhorst-Pack k-points used for the optical properties calculation by using k-point set dropdown list.
Click the More... button to open the CASTEP Core Level Spectroscopy Options dialog.
Select the Core level spectroscopy k-points option you want to use and the Band energy tolerance.

CASTEP calculations with core holes assume by default that an electron is removed from the system, so it is treated as having a charge of 1 (or one more than specified in the Charge field on the Setup tab of the CASTEP Calculation dialog). In some circumstances, for example when studying impurities, it might be more appropriate to consider the system as charge neutral. In order to achieve this you should specify the Charge of -1 on the Setup tab, in this way the CASTEP input file will have a zero charge. It is also possible to edit the seedname.param file to specify a fractional charge. The strength of the core hole can be adjusted by editing the seedname.cell file and modifying the pseudopotential definition string (for example, change {1s1} to {1s0.5} to use a core hole with the charge of 0.5).

Requesting core level spectroscopy

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