Beschreibung angeregter Molekülzustände in komplex strukturierter Umgebung durch einen effizienten, individuell selektierenden MRCI-Algorithmus gekoppelt an ein molekularmechanisches Kraftfeld

Atomistic theoretical descriptions of thermal chemical recations in
complex environments are well achieved by combined quantum and
molecular mechanical (QM/MM) methods. The goal of this work is to
extend such techniques to enable the description of photochemical
reactions and to carry out case studies subsequently. In order to
tackle the enormous computational demand due to the involvement of
excited electronic states, we (i) largely speed up the individually
selecting multi-refernce configuration interaction (IS/MRCI) scheme
by Tavan and Schulten (1980) by a new grahical algorithm and (ii)
take use of recently developed semimempirical valence shell models
(Thiel 1997) which are well suited for excited electronic states.
The efficiency and accuracy of the resulting IS/MRCI-algorithm is
demonstrated by its application to the first electronic excited
states of butadiene. The new QM/MM method is used to calculate
absorption energies along a molecular dynamics trajectory of a
small Schiff base in isotonic solution.