Crystal structure refinement of magnesium zinc divanadate, MgZnV2O7, from powder X-ray diffraction data

The crystal structure of magnesium zinc divanadate, MgZnV 2 O 7 , was determined and refined from laboratory X-ray powder diffraction data. The title compound was synthesized by a solid-state reaction at 1023 K in air. The crystal structure is isotypic with Mn 0.6 Zn 1.4 V 2 O 7 ( C2 / m ; Z = 6) and is related to the crystal structure of thortveitite. The asymmetric unit contains two metal sites with statistically distributed magnesium and zinc atoms with the atomic ratio close to 1:1. One (Mg/Zn) metal site ( M 1) is located on Wyckoff position 8 j and the other ( M 2) on 4 h . Three V sites (all on 4 i ), and eight O (three 8 j , four 4 i , and one 2 b ) sites complete the asymmetric unit. The structure is an alternate stacking of V 2 O 7 layers and (Mg/Zn) atom layers along [20\overline{1}]. It is distinct from other related structures in that each V 2 O 7 layer consists of two groups: a V 2 O 7 dimer and a V 4 O 14 tetramer. Mixed-occupied M 1 and M 2 are coordinated by oxygen atoms in distorted trigonal bipyramidal and octahedral sites, respectively.