Critical effect of local pressure on jump frequencies in intermetallics

Through an extensive atomic-scale investigation of NiAl3, a cementite-like structure, we show that only a proper account of saddle-point pressures leads to unambiguous jump attempt frequency spectra. We also demonstrate that attempt frequencies can spread over ranges exceeding five orders of magnitude and therefore cannot be realistically described by simplified few-valued schemes, as commonly assumed. These issues cast doubt on generally admitted assumptions in kinetic simulations, which may have critical consequences on their accuracy.