A high-accuracy theoretical study of the CH(n)P systems n = 1-3.

We have performed high-level electronic structure computations on the most important species of the CH(n)P systems n = 1-3 to characterize them and provide reliable information about the equilibrium and vibrationally averaged molecular structures, rotational constants, vibrational frequencies (harmonic and anharmonic), formation enthalpies, and vertical excitation energies. Those chemical systems are intermediates for several important reactions and also prototypical phosphorus-carbon compounds; however, they are often elusive to experimental detection. The present results significantly complement their knowledge and can be used as an assessment of the experimental information when available. The explicitly correlated coupled-cluster RCCSD(T)-F12 method has been used for geometry optimizations and vibrational frequency calculations. Vibrational configuration interaction theory has been used to account for anharmonicity effects. Basis-set limit extrapolations have been carried out to determine accurate thermochemical quantities. Electronic excited states have been calculated with coupled-cluster approaches and also by means of the multireference configuration interaction method.