Abstract: An advanced experimental and theoretical model to explain the correlation between the electronic and local structure of Eu2+ in two diferent environments within a same compound, EuS, is presented. EuX monochalcogenides (X: O, S, Se, Te) exhibit anomalies in all their properties around 14 GPa with a semiconductor to metal transition. Although it is known that these changes are related to the 4f 75d0 ?4f 65d1 electronic transition, no consistent model of the pressure-induced modifcations of the electronic structure currently exists. We show, by optical and x-ray absorption spectroscopy, and by ab initio calculations up to 35 GPa, that the pressure evolution of the crystal feld plays a major role in triggering the observed electronic transitions from semiconductor to the half-metal and fnally to the metallic state.

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