On europium digallides

Abstract The europium gallide Eu 1‐x Ga 2+3x ( x is between 0.06 and 0.07) has been synthesized and its crystal structure has been refined from single crystal X‐ray diffraction data. Eu 1‐x Ga 2+3x crystallizes with hexagonal structure related to the AlB 2 ‐type (space group P 6/ mmm , a =4.354 Å, c =4.485 Å). The structure refinement finished with R (F)=0.015 for 1603 reflections revealing a defect occupation of the Eu position (93 %) and additional Ga position, yielding the non‐integer element ratio. From magnetic susceptibility measurements, EuGa 2 and Eu 1‐x Ga 2+3x phases show the 4 f 7 (Eu +2 ) oxidation state. The analysis of effective atomic charges within the Quantum Theory of Atoms in Molecules reveals the formation of four‐bonded Ga species with low electron demand (in comparison to the three‐bonded in AlB 2 ‐type and four‐bonded in the KHg 2 ‐type structures) and shows, that Eu 1‐x Ga 2+3x represents a new way of stabilizing intermetallic structures formed at valence electron concentration, which does not allow to apply Zintl‐like electron counting.