Self-diffusion in sodium under pressure revisited.

The pressure-volume relation in sodium has been measured up to 100 GPa using high-resolution angle-dispersive synchrotron x-ray diffraction (Hanfland et al 2002 Phys. Rev. B 65 184109). In the light of these data, we show that a model suggested long ago (e.g., Varotsos et al 1978 J. Phys. C: Solid State Phys. 11 L305-15) can satisfactorily answer the long-standing question of the variation of the diffusion coefficient D under pressure P, which resulted in a curved lnD versus P plot, in the frame of a single operating mechanism (monovacancies). This is achieved without using any adjustable parameters.