CRYSTAL-STRUCTURE OF THE PHOSPHORUS OXYNITRIDE P4ON6

The ab initio crystal structure determination of the phosphorus oxynit ride P4ON6 has been performed by the X-ray powder diffraction techniqu e (space group Pnnm; a 6.8424(1)Angstrom, b = 6.0714(2)Angstrom, c = 6 .8176(1)Angstrom, Z = 2; R(Bragg) = 4.8%, Gof = 1.35) A structure refi nement of neutron data incorporating anisotropic temperature coefficie nts for oxygen and nitrogen reduces the R(Bragg)-factor down to 2.2% ( Gof = 1.35). P atoms are more or less rigid at room temperature. Signi ficant oxygen/nitrogen exchange was observed for one of the symmetrica lly different N sites (9 +/- 5%). A remarkable modulation of the diffu se background reflects considerable disorder in the structure not anal yzed so far. The structure is formed by PON3 and PN4 tetrahedra. PN4 t etrahedra are linked in pairs via a joint edge, which is a unique phen omenon among inorganic phosphorus-nitrogen compounds. (C) 1995 Academi c Press, Inc.