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dr. Marcel Nooijen: Transform & Diagonalize (T&D) approaches to electronic structure with applications to molecular spectroscopy

Wanneer:wo 30-04-2014 11:00 - 12:00
Waar:5111.0006

abstract

One of the remaining open challenges for quantum chemistry concerns the routine calculation of molecular systems that require a multireference description, and the simulation of their spectroscopic properties. Most notoriously are molecules containing one or more transition metal atoms. I will describe a very recent coupled cluster approach that enables the calculation of a large number of electronic states -100’s - based on a single state-averaged CASSCF, a single set of ‘cluster’ amplitudes that describe short-range correlation, and a compact CI diagonalization of a transformed Hamiltonian. The family of transform & diagonalize approaches have been implemented in both the ACESII and ORCA electronic structure packages using advanced automation techniques. Similar conceptual T&D techniques have been developed over the years for single reference systems (EOMCC and STEOM-CC) and I will show the latest applications to Rydberg/Valence excited states as well as a consideration of vibronic structure in photo-electron spectroscopy.