Simulating x-ray absorption spectroscopy with DFT methods

Yansun Yao

Abstract:
We have developed a computer program for the calculation of x-ray absorption spectroscopy (XAS) within the framework of density functional theory (DFT), employing the projector augmented wave (PAW) method. The code is implemented in the Quantum ESPRESSO package and take advantage of the reconstructed all electron wave functions computed by the GIPAW module. Presently, XAS is simulated by using the dipole approximation, but higher-order multipoles can be easily accounted for and included in the calculation. After introducing the theoretical foundations of XAS, I will present results for a simple test case, focusing on the C K-edge of diamond and comparing our results with the literature and experiment. Moreover, I will show the effect of various approximations used to simulate the core-hole.