✍ Scribed by Maxence Launay; Richard Dronskowski
No coin nor oath required. For personal study only.
Quasi‐ternary cyanamides and carbodiimides of general formula AB(NCN)~3~ with A ≠ B have neither been predicted nor synthesized. Thus, hypothetical compounds of that kind containing 3__d__ transition metals were considered (A = Ti, B = Mn, Fe, Co, Ni, Cu) by means of density‐functional calculations on 34 structural models, most of which were derived from chemically related phases. After performing structure optimizations based on the local‐density approximation, the relative energetic orderings are rationalized in terms of geometrical factors such as molar volumes and polyhedral connections. Total‐energy generalized‐gradient calculations evidence that the most stable models are enthalpically favored with respect to the elements. Even at ambient temperatures, the ternary phases are predicted as being thermodynamically stable in terms of their Gibbs free formation energies, especially if energetically competing and low‐lying binaries (TiC, TiN) can be excluded by a kinetic reaction control. The best models are characterized by low‐spin magnetic transition metals found in octahedral coordination, and the TiN~6~ and __M__N~6~ polyhedra either share faces or edges. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1180–1188, 2005
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