Theoretical X-Ray Spectroscopy
With the aim to uniquely correlate spectroscopic properties to electronic structure and geometric properties of target materials, we are working closely with the experimental X-ray spectroscopy groups of the neighbor MPI-CEC institute and employ in house developed wavefunction based methods in an effort to evaluate unique spectroscopic signatures of transition metal complexes and materials in both equilibrium and under operando conditions. This requires to use methods that do not belong in the standard arsenal of quantum chemistry. Over the last years we have developed and employed the restricted open shell configuration interaction singles methods (ROCIS and PNO-ROCIS) and their parameterized versions, (ROCIS/DFT and PNO-ROCIS/DFT) to compute a large variety of XAS and valence to core resonance X-ray emission spectra (VtC-RXES) of classes of chemical systems ranging between molecules to ‘real-life’ molecular and solid systems. Recently even more accurate computational protocols based on the complete active space configuration interaction in conjunction with N-electron valence second order perturbation theory (CASCI/NEVPT2) as well as multireference configuration interaction (MRCI) and multireference equation of motion coupled cluster (MREOM-CC) methods have been employed to compute challenging metal L-edge XAS spectra of medium sized molecules with high predictive accuracy.
Roemelt, M.; Maganas, D.; DeBeer, S.; Neese, F., A Combined Dft and Restricted Open-Shell Configuration Interaction Method Including Spin-Orbit Coupling: Application to Transition Metal L-Edge X-Ray Absorption Spectroscopy. The Journal of chemical physics 2013, 138, 204101.
Maganas, D.; DeBeer, S.; Neese, F., A Restricted Open Configuration Interaction with Singles Method to Calculate Valence-to-Core Resonant X-Ray Emission Spectra: A Case Study. Inorganic chemistry 2017, 56, 11819-11836.
Maganas, D.; DeBeer, S.; Neese, F., Pair Natural Orbital Restricted Open-Shell Configuration Interaction (PNO-ROCIS) Approach for Calculating X-Ray Absorption Spectra of Large Chemical Systems. The Journal of Physical Chemistry A 2018, 122, 1215-1227.
Chantzis, A.; Kowalska, J. K.; Maganas, D.; DeBeer, S.; Neese, F., Ab Initio Wave Function-Based Determination of Element Specific Shifts for the Efficient Calculation of X-Ray Absorption Spectra of Main Group Elements and First Row Transition Metals. Journal of chemical theory and computation 2018, 14, 3686-3702.
Maganas, D.; Kowalska, J. K.; Nooijen, M.; DeBeer, S.; Neese, F., Comparison of Multireference Ab Initio Wavefunction Methodologies for X-Ray Absorption Edges: A Case Study on [Fe(II/III)Cl4]2–/1– Molecules. The Journal of chemical physics 2019, 150, 104106.