A quarter of the century ago Bardeen and Herring showed that vacancies diffuse more ``effectively'' than atoms because the atoms are impeded by the occurrence of correlation. This difference in behavior is not evident in the elementary act of the vacancy mechanism of diffusion (the exchange of a vacancy with a neighboring atom of metal 1) which leads to equal but opposite interchange fluxes, I1° = -Iv°. For tracer diffusion in pure metal 1, however, the effective gross fluxes are J1° = -fJv°, where f is the correlation factor. This result is obtained analytically and has been corroborated by a computer simulation of tracer diffusion. For steady-state isothermal electromigration in pure metal 1, the net fluxes are J1 = -f1Jv, clearly demonstrating the impeding action of correlation on the diffusion of atomic species. The implications of the latter result for present diffusion theory are briefly discussed.
(Received May 1, 1978)
* Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, U.S.A.
© 2002 The Japan Institute of Metals
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