Dynamical algebraic diagrammatic construction approach for X-ray photoelectron spectra
Samragni Banerjee and Alexander Yu. Sokolov
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
X-ray photoelectron spectroscopy (XPS) has emerged as a useful tool for characterizing geometric and electronic structures of molecules. However, it is often difficult to simulate XPS spectra as they correspond to higher regions in the energy spectrum. In this work, we present a new approach for direct simulation of XPS spectra based on algebraic diagrammatic construction (ADC) theory. Conventional ADC formalisms require diagonalization of a secular matrix, which becomes computationally expensive when solving for higher eigenvalues of the Hamiltonian matrix. In our approach, termed dynamical ADC (d-ADC), we compute the spectral function directly by solving a system of linear equations at each frequency of the perturbing external field. Our implementation of d-ADC for ionization energies enables us to simulate XPS spectra directly, without any additional approximations, such as core valence separation (CVS). We briefly discuss the theory for this new approach and show our numerical results for several benchmark systems. Finally, we compare d-ADC results to the ones obtained with core-valence separated ADC.