Penta-potassium praseodymium(III) dilithium deca-fluoride, K(5)PrLi(2)F(10).

The crystal structure of K(5)PrLi(2)F(10) is isotypic with those of other K(5)RELi(2)F(10) compounds (RE = Eu, Nd). The lanthanoid ions are isolated in K(5)PrLi(2)F(10), with a mean separation between the Pr ions of 7.356 Å. It classifies this crystal as a so-called self-activated material containing lanthanoid ions within the matrix. Except for two K(+) and two F(-) ions, all atoms are located on sites with m symmetry. In the structure, distorted PrF(8) dodeca-hedra and two different LiF(4) tetra-hedra share F atoms, forming sheets parallel to (100). The isolated PrF(8) dodeca-hedra exhibit a mean Pr-F distance of 2.406 Å. The K(+) cations are located within and between these sheets, leading to highly irregular KF(x) polyhedra with coordination numbers of eight and nine for the alkali metal cations.