Can NO2+ exist in bent or cyclic forms?

Calculations of NO2+ at HF, CBS-4, CASSCF, MBPT(2), MBPT(3), and MBPT(4) th eory levels, using 3-21G and 6-31G(d) basis sets, found two C-2V structures along with the linear geometry. Computations using MBPT(2) and CCSD(T) app roaches and the aug-cc-pvtz basis set confirmed these results. Harmonic vib rational frequency calculations, performed with MBPT(2) and CCSD(T) theorie s, indicated that the linear structure was the global minimum while one of the bent structures (angle ONO = 80 degrees) was a higher energy local mini mum. The second C-2V structure (angle ONO = 45 degrees) exhibited a large i maginary vibrational frequency along the asymmetric stretching (B-2) mode, indicating its saddle point nature. (C) 2001 Elsevier Science B.V. All righ ts reserved.