An ab initio study of vibrational corrections to the electrical propertiesof the fluoromethanes: CH3F, CH2F2, CHF3 and CF4

Accurate SCF and MP2 quartic property hypersurfaces have been computed for the energy, dipole moments, quadrupole moments and polarizability tensors o f the fluorinated methanes CF4, CHF3, CH2F2 and CH3F, to establish accurate values of zero-point vibrational corrections to the properties. Using a co nsistent set of r(e) geometries from density functional theory, these ZPVCs are coupled with accurate electrical properties computed using a range of correlated methods, especially BD and BD(T), and a number of purpose-built polarized basis sets, to obtain near definitive estimates of these properti es that incorporate the effects of vibrational averaging. Careful attention has been paid to a critical comparison between these theoretical estimates and experimental measurements, and agreement between the two is shown to b e exceptionally good. In particular, it is clear that in many instances mor e precise experimental results would be required in order to discriminate b etween different correlated results, or between the present results and tho se which may be obtained with larger basis sets. The work highlights the ne cessity to allow for the effects of zero-point vibrational averaging when c omparing theory with experiment, or even when comparing different theoretic al results with one another using experiment as a benchmark. It also points to the need for further precise experimental measurements of some of these properties.