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V 16 N 1.5 : Metastable or Missing in the Binary Phase Diagram?
Author(s) -
Widenmeyer Marc,
Wessel Claudia,
Dronskowski Richard,
Niewa Rainer
Publication year - 2015
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201500620
Subject(s) - metastability , phase diagram , vanadium , thermodynamics , thermal decomposition , homogeneity (statistics) , thermal stability , decomposition , chemical stability , atmospheric temperature range , chemistry , argon , materials science , phase (matter) , analytical chemistry (journal) , inorganic chemistry , physics , organic chemistry , statistics , mathematics
The stability of V 16 N 1.5 was investigated by experiments and density functional calculations. Three synthetic approaches besides the classical reaction of vanadium with flowing ammonia were evaluated: (i) The ammonolysis of β‐V 2 H, (ii) the reaction of vanadium and δ‐VN at elevated temperatures in sealed ampoules, and (iii) the thermal decomposition of δ‐VN in dynamic vacuum at high temperatures. However, none of them was suitable to provide single phase V 16 N 1.5 yet. The results achieved by experiments and by simulations both indicate an absence of significant homogeneity range for V 16 N 1.5 . The high‐temperature experiments suggest a strongly enhanced thermal stability for V 16 N 1.5 than reported in literature, suggesting V 16 N 1.5 to represent a thermodynamically stable compound rather than being metastable. Temperature dependent powder X‐ray diffraction proves stability of V 16 N 1.5 up to 700 °C. During a thermal analysis experiment in argon V 16 N 1.5 was still observed after 24 h at 1300 °C. Consequently, first‐principle calculations of the thermodynamic properties of V 16 N 1.5 revealed an endothermal decomposition to V and β‐V 2 N.