Simon's department emphasized the investigation of metal-metal bonding with main group, d- and f-metals. The work focussed on the development of structural concepts (e.g., condensed cluster concept) and the search for new materials, their phase relationships and connections between structure, chemical bonding and properties with metal-rich compounds of transition metals, particularly oxides and halides, reduced rare earth metal halides, hydride, carbide, boride, boride carbide, aluminide and silicide halides of the rare earth metals, alkali and alkaline earth metal suboxides and subnitrides. Electron microscopy was used to characterize microcrystalline phases up to full structure refinement as well as analysis of real structure. A chemical view on superconductivity in terms of a tendency towards pair-wise localization of carriers in a flat band–steep band scenario was worked out. New colossal magnetoresistance materials resulted from an interplay of d- and f-electrons.
Simon retired in January 2010.