Synthesis and crystal structure determination of a new misfit compound:: [(EuS)1.5]1.15NbS2

The crystal structure of the new misfit compound [(EuS)(1.5)] 1.15NbS2 has been determined via the composite approach. The structure is built up from three [EuS] layers (= slab noted 'Q') alternating with the [NbS2] sandwich (= slab noted 'H') along the stacking direction (c axis). The cell parameters (Angstrom) of this composite structure are: Q-part, a = 5.760(1), b = 5.780(1), c = 29.734(5); H-part, a = 3.317(1), b = 5.790(1), c = 14.859(4). Eu atoms located on the exterior sides of the Q-part show a quite regular hemi-octahedral coordination, whilst the inner Eu atoms show g distorted octahedral coordination. From bond valence calculations, one can assume that the outer Eu atoms are at the +II oxidation state and the inner Eu atoms at the +III state. The structure of the H-part appears very comparable to that found for other misfit compounds, i.e., Nb atoms in a trigonal prismatic coordination with S atoms, as for the binary NbS(2 )itself. (C) Academie des Sciences/Elsevier, Paris.