A study on the GVFF of CHF3, CH2F2, and CH3F

The complete GVFF of CHF₃, CH₂F₂, and CH₃F has been calculated from self-consistent-field ab initio energies, using a 4–31 G basis set. The larger part of the interaction force constants is close to those of the best available force fields from experimental data. Only one interaction term in CH₃F and the interaction force constants of the A₁ species in CH₂F₂ differ appreciably from the experimental ones. Using constraints from the ab initio studies we have improved the GVFF of CH₃F and CH₂F₂. It is shown that all comparable stretch-stretch interaction terms are of the same order of magnitude in the three molecules. The sign of all stretch/bend force constants are in accordance with those predicted by the hybrid orbital force field.