Quantum chemical bonding descriptors have recently been utilized to design materials with tailored properties. We will review their usage to facilitate a quantitative description of bonding in chalcogenides as well as the transition between different bonding mechanisms. More importantly, these descriptors will also be employed as property predictors for several important material characteristics, including optical and transport properties. Hence, these quantum chemical bonding descriptors can be utilized to tailor material properties of chalcogenides relevant for thermoelectrics, photovoltaics and phase change memories.Relating material properties to bonding mechanisms also shows that there is a class of materials, which are characterized by unconventional properties such as a pronounced anharmonicity, a large chemical bond polarizability, and strong optical absorption. This unusual property portfolio is attributed to a novel bonding mechanism, fundamentally different from ionic, metallic and covalent bonding, which has been called 'metavalent'. In the concluding chapter, a number of promising research directions are sketched, which explore the nature of the property changes upon changing bonding mechanism and extend the concept of quantum chemical property predictors to more complex compounds.

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