Temperature-Dependent Activation Volumes in Zinc

Precision measurements of self-diffusion in zinc as a function of pressure indicate that the activation volumes ΔVc and ΔVb respectively associated with the nonbasal and basal vacancy jumps have a temperature dependence given by (∂ΔVc∂T)ₚ=(6.2±1.9)×10^-3 cm³/mole ^∘{}K and (∂ΔVb∂T)ₚ=(7.6±3.4)×10^-3 cm³/mole ^∘{}K. A model calculation based on a Morse-like potential indicates that the frequencies of atomic vibrations in the vicinity of the defect vary with pressure in a way that is consistent with these experimentally measured quantities.