Electronic excited states of benzene in interaction with water clusters: influence of structure and size

This work is dedicated to the theoretical investigation of influence water clusters’ organisation and size on electronic spectrum an interacting benzene (Bz) molecule using both TD-DFT CASPT2 approaches. Two series geometries, namely $$Geo_{IEI}$$ $$Geo_{IED}$$ were extracted from two Bz-hexagonal ice configurations leading maximum minimum ionization energies respectively. An appropriate basis set containing atomic diffuse polarisation orbitals describing Rydberg states Bz was determined. The approach carefully benchmarked against results for smallest systems. Despite some discrepancies, trends found be similar at levels theory: positions intensities main $$\pi \rightarrow \pi ^{\star }$$ transitions slightly split due symmetry breaking. For systems, our clearly show dependence structures. Of particular interest, low energy non negligible oscillator strength a $$\pi$$ orbital virtual character, also involving functions partially expanded cluster, series. such determined more than 2 eV below potential Bz. When cluster’s increases, all structures, becoming mainly developed H atoms molecules edge cluster. Given their nature energy, could play role in photochemistry aromatic species interaction with clusters or ice, processes being astrophysical interest.