The crystal structure of silver azide (AgN3) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 degrees C and was further refined by the Rietveld method. The structure is monoclinic (P21/c (No. 14), a = 6.0756(2) A, b = 6.1663(2) A, c = 6.5729(2) A, beta = 114.19(0) degrees, V = 224.62(14) A3, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.

No abstract

No abstract

No abstract

Cyanogen isocyanate (NC–NCO) has been prepared and studied using a combined experimental and theoretical approach. A crystalline film of the interpseudohalogen species was stabilized by vapor deposition on a cold substrate (T = –100 °C). From IR spectroscopy on the “free” molecule, trapped in a matrix of solid argon, the connectivity and geometry of this unstable interpseudohalogen was deduced and substantiated by theoretical calculations. With this information, the crystal structure of NCNCO in the solid state could be analysed using powder X‐ray diffraction [Pbca (No. 61), a = 7.63(1) Å, b = 6.50(2) Å, c = 6.03(6) Å; V = 299.5(1) Å3]. The compound transforms into amorphous polymeric C2N2O at T > –68 °C. The results obtained were compared with recent findings and further discussed in the general context of C–N–(O) chemistry.