Solid solutions of C in the face-centered cubic Ni-Fe matrix exhibited an anomaly which manifested itself as a peak in the variation of the activation energy for diffusion and the partial enthalpy of dissolved C atoms as a function of composition. This peak, which occurred at 0.25 to 0.3at%Fe, was shown to be related mainly to volume changes in the Ni-Fe matrix, rather than to effects which were related to the electronic states of the Fe atoms.

R.B.McLellan, L.Yang: Journal of the Physics and Chemistry of Solids, 1994, 55[11], 1227-32