title: Crystal structures of cristobalite-type and coesite-type PON redetermined on the basis of single-crystal X-ray diffraction data.
abstract: Hitherto, phospho-rus oxonitride (PON) could not be obtained in the form of single crystals and only powder diffraction experiments were feasible for structure studies. In the present work we have synthesized two polymorphs of phospho-rus oxonitride, cristobalite-type (cri-PON) and coesite-type (coe-PON), in the form of single crystals and reinvestigated their crystal structures by means of in house and synchrotron single-crystal X-ray diffraction. The crystal structures of cri-PON and coe-PON are built from PO2N2 tetra-hedral units, each with a statistical distribution of oxygen and nitro-gen atoms. The crystal structure of the coe-PON phase has the space group C2/c with seven atomic sites in the asymmetric unit [two P and three (N,O) sites on general positions, one (N,O) site on an inversion centre and one (N,O) site on a twofold rotation axis], while the cri-PON phase possesses tetra-gonal I-42d symmetry with two independent atoms in the asymmetric unit [the P atom on a fourfold inversion axis and the (N,O) site on a twofold rotation axis]. In comparison with previous structure determinations from powder data, all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles.
authors.affiliation: Bayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Maxim
authors.initials: M
authors.lastname: Bykov
authors.affiliation: Bayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Bykova
authors.affiliation: ESRF, 38043 Grenoble, France.
authors.forename: Vadim
authors.initials: V
authors.lastname: Dyadkin
authors.affiliation: Department of Chemistry, Ludwig Maximilian University, 81377 Munich, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Baumann
authors.affiliation: Department of Chemistry, Ludwig Maximilian University, 81377 Munich, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schnick
authors.affiliation: Bayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Leonid
authors.initials: L
authors.lastname: Dubrovinsky
authors.affiliation: Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth, 95440 Bayreuth, Germany.
authors.forename: Natalia
authors.initials: N
authors.lastname: Dubrovinskaia
keywords: crystal structure; phospho­rus oxonitride; redetermination; silica analogues