Anharmonic force fields of bromofluoromethane

High-level ab initio calculations with relatively large basis sets are reported for bromofluoromethane, CH2BrF. Correlated harmonic and anharmonic force constants are obtained from several levels of theory including second-order Moller-Plesset perturbation and coupled cluster CCSD(T). Density functional theory and to be more precise the B3LYP functional, is also employed. Results are used to determine a number of anharmonic molecular properties, including vibration-rotation interaction constants, vibrational anharmonicity constants, fundamental vibrational frequencies, sextic centrifugal distortion constants and rotational constants which include zero-point corrections. Good agreement with available experimental data is found combining coupled cluster CCSD(T) optimized geometry and harmonic force field with cubic and quartic force constants obtained at MP2 level of theory, a cost-effective computation in terms of time. Moreover, transformations of the force. elds in mass-independent internal coordinate force constants suitable for other isotopologues of CH2BrF are also investigated.