Theoretical core-level excited spectra with inclusion thick red line and without inclusion thin blue line of the core-hole effects.
CASTEP can calculate spectra involving transitions between core and conduction states (ELNES, XANES). Core-hole effects can be taken into account by using supercells and pseudopotential generated with a reduced occupancy.
CASTEP can also compute the complex dielectric function with the random phase approximation (neglecting local field effects). This can be used to obtain the refractive index and optical conductivity. It can also be used to obtain the loss function, providing a connection to low-loss EELS.
For more information on Core-loss and Optical properties in CASTEP see the following talks from the 2009 Castep workshop:
- The power of Core-loss spectra Dr Rebecca Nicholls (Oxford)
- Theory of Core-loss spectra Prof Chris Pickard (UCL)
- Application of Core-loss spectra Dr Rebecca Nicholls (Oxford)
- Theory of core-hole effects in 1s core-level spectroscopy of the first-row elements Shang-Peng Gao, Chris J. Pickard, Mike C. Payne, Jing Zhu and Jun Yuan Phys. Rev. B 77, 115122 (2008)