Jean-François Halet's research centers on the understanding of the chemical bond in transition metal inorganic chemistry. He uses a variety of quantum chemical computational tools such as Extended Hückel, Ab initio and Density Functional methods to tackle problems of electron-counting, structure, physical properties and reactivity of both molecular and solid state systems. When possible, structural similarities between molecular and solid state compounds are analyzed. The main recent investigations of J.-F. Halet concern (i) The electronic structure of large (molecular, nanosized, and solid-state) inorganic transition metal clusters; (ii) The study of the metal-to-carbon bonding and physical properties in polymetallic compounds containing carbon ligands; (iii) The understanding of the structural arrangement and the physical properties, especially thermoellectrical properties, of solid-state compounds such as borides, boride carbides and nitrides.