ICAMS / Interdisciplinary Centre for Advanced Materials Simulation
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The six-jump diffusion cycles in B2-compounds

R. Drautz, B. Meyer, M. Fähnle.

Diffusions in Materials: DIMAT2000, PTS 1 & 2, 194-1, 417-422 , (2001)

Abstract
The self-diffusion in B2 compounds AB via six jump cycles is investigated by using elementary properties of stochastic processes. The ratios D-A/D-B of the self-diffusion coefficients for the two components and P-110/P-100 of the probabilities for effective jumps via 110 or 100 cycles have been derived by Arita et al. for an idealized six jump model where the energetics is assumed to be the same for all three geometrically different six jump cycles in the B2 structure. Based on these limits the experimental ratios often have been used to explore whether self-diffusion via six jump cycles is in principle relevant for the special investigated B2 compounds. In contrast, we will show that the limits for D-A/D-B are at least considerably widened and that for P-110/P-100 no limits at all can be established when abandoning the unrealistic assumptions of the idealized model. It is demonstrated by ab-initio density functional calculations for NiAl that strong deviations from the idealized model are probably the rule and not the exception.


Keyword(s): B2-NiAl; self-diffusion in intermetallic compounds; six-jump-cycle
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