How to Validate Choice of DFT Functionals and Basis Sets for atomic charge calculation of Fluorocarbons

I need to calculate the charges (electron densities) on each atom of a set of partially fluorinated hydrocarbon molecules by NPA. The question arises:


What is the currently accepted / best practice method for validating these calculations as a function of Functional and Basis Set for DFT based calculations? Since no "experimental" values for electron densities are available, I have tried evaluating the "correctness" of the chosen functional and basis set by correlating the predicted bond lengths and bond angles to experimental values. However, this seems to be far too simplistic to provide a meaningful estimation of the correctness of the choice.


