Data by NMR and Representations of Self-Diffusion Coefficients in Carbon Tetrafluoride and the Determination of Intermolecular Force Constants

Abstract

Self-diffusion coefficients were measured by the pulsed nuclear magnetic resonance method for pure carbon tetrafluoride for the conditions −30 to 75°C and 20–440 atm. As predicted by the dilute gas theory, the density—diffusivity product (ρD) versus density (ρ) at constant temperature was found to be almost constant up to a reduced density of about 0.4, above which ρD started decreasing sharply. Based on the corresponding states principle, three semiempirical representations for the data were developed and compared. The low-density data were used, along with previously published second virial coefficient data, to evaluate intermolecular force constants for the Lennard-Jones (6–12) potential and the modified Buckingham (6-exp) potential.