The self-diffusion of 63Ni in monocrystals of the ordered intermetallic compound was investigated (table 202). It was found that the activation energies for diffusion perpendicular to, and parallel to, the hexagonal c-axis were almost the same and lay between 2.14 and 2.34eV:

Ni64In36,  c-axis:     D(cm2/s) = 63.2 exp[-2.31(eV)/kT]

Ni64In36, || c-axis:     D(cm2/s) = 108 exp[-2.34(eV)/kT]

Moreover, the Do values were direction-dependent and ranged from 65 to 110cm2/s. The experimental values of the D/D ratio were between 0.87 and 0.79; depending upon the temperature. It was suggested that the principal diffusion mechanism should be a site change of the tracer atom between the Ni chains in the c-direction and the double tetrahedral interstices, with a further jump to another chain. However, 2 other minor mechanisms were possible. With increasing temperature, and filling of the double tetrahedral interstices, the importance of the minority mechanisms increased.

H.Schmidt, G.Frohberg, H.Wever: Acta Metallurgica et Materialia, 1992, 40[11], 3105-11