The structure of astatine azide, AtN3—A theoretical study
Tóm tắt
For the first time theoretical evidence for the experimentally hitherto unknown astatine azide, AtN3, the heaviest of all halogen azides, is presented. The structure and the vibrational data of AtN3 were computedab initio at RHF and electron-correlated MP2 levels of theory using a quasirelativistic (MWB) pseudopotential for astatine, where the basis functions for the valences andp electrons consist of the standard double-ζ basis set. For nitrogen a standard 6-31G(d) basis was used. The molecule represents a true minimum (NIMAG=0) at all levels of theory applied and is predicted to exist in a planartrans bentC
s
structure. Since hybrid functionals, which define the exchange functional as a linear combination of Hartree-Fock, local, and gradient-corrected exchange terms, are known to predict the experimental parameters best, we also computed astatine azide (At-N1-N2-N3) at the B3-LYP level; the results are as follows:d(At-N1)=2.267,d(N1–N2)=1.239,d(N2–N3)=1.146 å; ∠(A1-N1-N2)=111.6‡, ∠(N1-N2-N3)=171.9‡;v
1,=157.4,v
2=366.6,v
3=559.0,v
4=659.6,v
5=1264.7,v
6=2165.1 cm−1 (unscaled). The heat of formation was computed at B3-LYP level to be δH
(AtN3)=+80 kcal mol−1.
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