Structure of the nitrosomethane molecule (CH3NO) in the ground electronic state:: Testing of ab initio methods for the description of potential energy surface

The equilibrium geometry, barrier to internal rotation, and harmonic and anharmonic vibrational frequencies of the CH3NO molecule in the ground electronic state were calculated by different modern quantum chemical techniques. Special attention was given to the problem of torsional motion. The dependence of the results of calculations on the atomic orbital and molecular orbital basis sets and correlated methods was examined. The results of calculations were compared with experimental data. Some methods provided excellent agreement with the experiment. (C) 2003 Wiley Periodicals, Inc.