Research Topics

Theoretical X-ray spectroscopy

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.

Representative Publications:

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.

Theoretical spectroscopic protocols for catalysis

Theoretical spectroscopic protocols for catalysis

An important activity in the group is to develop valid spectroscopic protocols that are able to treat relevant problems that are met in the fields of homogeneous and heterogeneous catalysis. The ultimate goal here is to develop a spectroscopic information content that is transferable between the homogeneous and heterogeneous catalysis worlds.

Representative Publications:

 Maganas, D.; Trunschke, A.; Schlögl, R.; Neese, F., A Unified View on Heterogeneous and Homogeneous Catalysts through a Combination of Spectroscopy and Quantum Chemistry. Faraday discussions 2016, 188, 181-197.

Kubas, A.; Noak, J.; Trunschke, A.; Schlögl, R.; Neese, F.; Maganas, D., A Combined Experimental and Theoretical Spectroscopic Protocol for Determination of the Structure of Heterogeneous Catalysts: Developing the Information Content of the Resonance Raman Spectra of M1 MoVO_x. Chemical science 2017, 8, 6338-6353.

 

Accurate ground and excited state energetics for solid systems

Accurate ground and excited state energetics for solid systems

As in addition to spectroscopy, reactivity plays an essential role in understanding the structure and the properties of catalytic active centers, the group shows activity in defining protocols that can deliver accurate energetics in problems similar to those met in solid state catalysis. In a characteristic example it has been recently shown that using the domain-based pair natural orbital local correlation concept (DLPNO-CCSD(T)), allows for ab initio calculations providing reference adsorption energetics at solid surfaces with an accuracy approaching 1 kcal/mol and at affordable computational cost. In a more recent example we have demonstrated that for both organic and inorganic semiconductors the back-transformed Pair Natural Orbital Similarity Transformed Equation of Motion Coupled-Cluster (bt-PNO-STEOM-CCSD) method provides the best agreement with the available experimental values resulting in errors that are on average lower than 0.2 eV.

Representative publications:
Kubas, A.; Berger, D.; Oberhofer, H.; Maganas, D.; Reuter, K.; Neese, F., Surface Adsorption Energetics Studied with “Gold Standard” Wave-Function-Based Ab Initio Methods: Small-Molecule Binding to TiO₂ (110). The journal of physical chemistry letters 2016, 7, 4207-4212. 

Dittmer, A.; Izsák, R. b.; Neese, F.; Maganas, D., Accurate Band Gap Predictions of Semiconductors in the Framework of the Similarity Transformed Equation of Motion Coupled Cluster Theory. Inorganic chemistry 2019.

Staff