The matlockite-type praseodymium(III) oxide bromide PrOBr

The crystal structure of the praseodymium(III) oxide bromide, PrOBr, can be best described with layers of agglomerated square antiprisms [PrO4Br4](9-). These slabs are stacked along the c axis and linked via two different secondary contacts between Pr3+ and Br-. The Pr3+ cations occupy the Wyckoff site 2c with 4mm symmetry and carry four O2- anions as well as four primary Br- anions, yielding a coordination number of 8. While the Br- anions exhibit the same site symmetry as the Pr3+ cations, the oxide anions are located at the Wyckoff position 2a with site symmetry (4) over bar m2 and have four Pr3+ cations as neighbours, defining a tetrahedron.