VANADIUM (V) MONOPHOSPHATE WITH A TUNNEL STRUCTURE: KV2O4PO4

摘要

A vanadium (V) monophosphate, KV2O4PO4, with an original tunnel structure has been synthesized. It crystallizes in the space group Pn21a, with a=13.924(1) angstroms, b=19.946(1) angstroms, c=4.749(1) angstroms. The [V2PO8]infinity framework consists of 90 degrees oriented [V2O8]infinity pyramidal chains running along a and c, respp. , interconnected by single PO4 tetrahedra. This framework delimits two sets of tunnels: large S-shaped and smaller eight-sided tunnels running along c and a, respp. The K+ cations are located approx at the intersection of these tunnels, with an eight- and nine-fold coordination, respp. The geometry of the chains of corner-sharing VO5 pyramids is compared to those of the octahedral chains in the perovskite and hexagonal tungsten bronze structures. The existence of two abnormally short V-O bonds per pyramid is emphasized and discussed. 21 refs.