A systematic density functional study of fluorination in methane, ethane and ethylene

The effect of fluorination on the physical and chemical properties of methane, ethane and ethylene has been investigated using semiempirical, standard ab initio and density functional methods, with particular emphasis on the adiabatic connection method (ACM), a hybrid HF-DFT procedure that mixes part of the exact Hartree-Fock exchange in with the density functional. The ACM functional is able to reproduce accurately all the structural and conformational changes that occur with fluorination, and overall gives the best agreement with experiment of all the theoretical approaches examined in this study.