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β‐Ca 3 N 2 , a Metastable Nitride in the System Ca–N
Author(s) -
Höhn Peter,
Hoffmann Stefan,
Hunger Jens,
Leoni Stefano,
Nitsche Fabian,
Schnelle Walter,
Kniep Rüdiger
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801857
Subject(s) - nitride , crystallography , octahedron , chemistry , crystal structure , corundum , electrical resistivity and conductivity , inorganic chemistry , mineralogy , physics , organic chemistry , layer (electronics) , quantum mechanics
A new page in the phase book : The metastable nitride β‐Ca 3 N 2 , the synthesis, crystal structure (see picture), and physical properties of which are reported, is an isotype of corundum (α‐Al 2 O 3 ). Vacancies in the crystal structure of β‐Ca 3 N 2 are discussed by using full‐potential local orbital methods and taking into account both the physical properties and the density of states.The structural chemistry of calcium nitrides is represented by just two different intermediate phases: cubic Ca 3 N 2 (referred to as α‐Ca 3 N 2 , Mn 2 O 3 type structure) and Ca 2 N (CdCl 2 type structure). Other binary phases (“γ‐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 β‐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. β‐Ca 3 N 2 transforms monotropically ( T trans ≈810 K) to cubic α‐Ca 3 N 2 . The crystal structure of β‐Ca 3 N 2 (rhombohedral R $\bar 3$ c , no. 167, a =619.884(3) pm, c =1662.958(10) pm) is an isotype of the corundum structure (α‐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 β‐Ca 3 N 2 is a diamagnetic semiconductor.