Crystal structure and f-orbital hybridization in the filled skutterudite PrRu₄P₁₂

The lattice dynamic of the filled skutterudite PrRu4P12 has been investigated by both Raman spectroscopy and density-functional theory (DFT) calculations, through the metal to insulator transition at 63 K. A P23 space group, which lacks inversion symmetry, is identified for the low temperature phase. The classical room-temperature Im (3) over bar structure reported in the filled skutterudite family is questioned in this compound. Our results point to the Pm (3) over bar space group, which already has two distinct Pr sites in the metallic state at room temperature. The consequences of symmetry breaking, between Pm (3) over bar and P23 on both the f orbital hybridization and the crystal schemes are discussed.