Subsystem TDDFT for spectra and response properties of molecular aggregates

Abstract

Quantum chemical studies on functional (bio)molecular assemblies are hampered by two basic problems: (i) The computational effort can be prohibitively large, and (ii) the analysis is complicated by the fact that properties of the entire aggregate are calculated. For the purpose of interpretation, however, it is often desirable to determine the contributions of certain subsystems to the calculated property. An example are theories of energy-transfer following absorption processes in pigment aggregates. Such theories work with effective parameters like site energies of pigments, excitonic coupling parameters, and solvent screening factors. In this talk, recent progress in the description of spectra and response properties of large molecular aggregates based on a subsystem approach to time-dependent density functional response theory will be discussed, which allows for an interpretation in terms of fragment properties. A special focus will be on environmental effects on excitonic coupling parameters in solvated pigment dimers and in protein-pigment complexes