title: Crystal structure of strontium dinickel iron orthophosphate.
abstract: The title compound, SrNi2Fe(PO4)3, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2), Fe is on 4b (2/m), Ni and the other P atom are on 8g (2), one O atom is on 8h (m) and the other on 8i (m). The three-dimensional framework of the crystal structure is built up by [PO4] tetra-hedra, [FeO6] octa-hedra and [Ni2O10] dimers of edge-sharing octa-hedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octa-hedra ([Ni2O10] dimer) linked to [PO4] tetra-hedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetra-hedra and FeO6 octa-hedra sharing apices. The layers are held together through vertices of [PO4] tetra-hedra and [FeO6] octa-hedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms.
authors.affiliation: Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco.
authors.forename: Said
authors.initials: S
authors.lastname: Ouaatta
authors.affiliation: Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco.
authors.forename: Abderrazzak
authors.initials: A
authors.lastname: Assani
authors.affiliation: Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Saadi
authors.affiliation: Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, BP 1014, Rabat, Morocco.
authors.forename: Lahcen
authors.initials: L
authors.lastname: El Ammari
keywords: SrNi2Fe(PO4)3; crystal structure; solid-state reaction synthesis; transition metal phosphates; α-chromium phosphate