SELF-DIFFUSION IN EICOSANE SINGLE-CRYSTALS

Radiotracer, serial sectioning studies of self-diffusion have been made in ultra-pure single crystals of the triclinic phase of n-eicosane (C//2//0H//4//2) in the temperature range 295-309 K. The crystals of this solid readily undergo plastic deformation. Consequently, crystals grown from the melt (Bridgman Technique) contain a high concentration of dislocations, slip bands and polygonized boundaries. Diffusion along these defects (pipe-diffusion) contributes significantly to the total penetration of radioactivity and hence decreases the precision with which lattice self-diffusion coefficients can be evaluated. An attempt made to assess this interference and to correct data is described showing that diffusion probably proceeds by vacancy migration.