Struktur und Bindungscharakter von Ba3P2

The structure of the compound Ba₃P₂ was elucidated. It cristallizes with the inverse Th₃P₄ structure, or strictly, with the inverse Ce₂S₃ structure with randomly distributed phosphorus vacancies. The lattice parameter a₀ is 9.775 Å, the x-ray density dx is 4.52 g/cm³. The coordinate parameter x of the barium sites is 0.0665. Barium is surrounded by 6 phosphorus and 5 barium atoms; the distance of 3,81 Å between 3 of the barium atoms is extremely short. Phosphorus is surrounded by 8 barium atoms. The phosphorus atoms are isolated from one another. The structure is best described as a filling of the octahedral spaces in the bee lattice of the barium metal by phosphorus atoms. The partially negative charge of the phosphorus atoms (P^? + 2e ? P^?? + e) causes a strong distortion of the interstitial lattice. The bonding character of Ba₃P₂ has to be interpreted as mixed metallic-ionic.