Self diffusion in compressed liquid chloromethane, dichloromethane and trichloromethane

Abstract

Self diffusion coefficients for CHCl₃, CH₂Cl₂ and CH₃Cl were measured with the N.M.R. spin-echo method at temperatures between 186 K and 440 K and pressures up to 200 MPa. The results are compared to theoretical models for diffusion processes and MD-simulations of the three compounds. From an Arrhenius plot activation volumes and activation energies are estimated. The experimental data can be described with the free volume model and the rough hard sphere model. The latter yields molecular diameters which are almost independent of temperature and translation-rotation coupling parameters which are strongly temperature dependent. The agreement with MD-simulation data is fair.