title: Beta-Ca3N2, a metastable nitride in the system Ca-N.
abstract: The structural chemistry of calcium nitrides is represented by just two different intermediate phases: cubic Ca(3)N(2) (referred to as alpha-Ca(3)N(2), Mn(2)O(3) type structure) and Ca(2)N (CdCl(2) type structure). Other binary phases ("gamma-Ca(3)N(2)", "Ca(11)N(8)") have been proven to represent cyanamide nitrides, Ca(4)N(2)[CN(2)] and Ca(11)N(6)[CN(2)](2), respectively. The metastable nitride beta-Ca(3)N(2) is prepared either by reaction of freshly distilled calcium metal with nitrogen at 700 K, or by reaction of Ca(2)N with N(2) at 500 K. beta-Ca(3)N(2) transforms monotropically (T(trans) approximately 810 K) to cubic alpha-Ca(3)N(2). The crystal structure of beta-Ca(3)N(2) (rhombohedral R3c, no. 167, a=619.884(3) pm, c=1662.958(10) pm) is an isotype of the corundum structure (alpha-Al(2)O(3)) and comprises a network of NCa(6/4) octahedra that share common faces and edges. Magnetic susceptibility and electrical resistivity measurements confirm that beta-Ca(3)N(2) is a diamagnetic semiconductor.
authors.affiliation: Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strasse 40, 01187 Dresden, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Höhn
authors.forename: Stefan
authors.initials: S
authors.lastname: Hoffmann
authors.forename: Jens
authors.initials: J
authors.lastname: Hunger
authors.forename: Stefano
authors.initials: S
authors.lastname: Leoni
authors.forename: Fabian
authors.initials: F
authors.lastname: Nitsche
authors.forename: Walter
authors.initials: W
authors.lastname: Schnelle
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Kniep