- Title
- The nature of the vacancy-wind effect occurring in diffusion via six- jump-cycles in B2 intermetallics
- Creator
- Belova, I. V.; Murch, G. E.
- Relation
- 5th International Conference on Diffusion in Solids and Liquids (DSL2009). Proceedings of the 5th International Conference on Diffusion in Solids and Liquids (Rome, Italy 24-26 June, 2009) p. 1218-1225
- Publisher Link
- http://dx.doi.org/10.4028/www.scientific.net/DDF.297-301.1218
- Publisher
- Trans Tech Publications
- Resource Type
- conference paper
- Date
- 2010
- Description
- First discovered by the late Dr John Manning, the vacancy-wind effect is a subtle phenomenon that occurs when two or more atomic species compete for vacancies in a net vacancy flux. The vacancy-wind effect is incorporated in (for example) the vacancy-wind or Manning factor that appears in the Darken-Manning Equation relating the interdiffusivity, the tracer diffusivities and the thermodynamic factor. The mechanism of the vacancy-wind phenomenon has long been very poorly understood. Recently, a moving reference frame Monte Carlo method was used to illustrate graphically how the vacancy-wind effect operates in both ionic conductivity in an ionic solid with a dilute solute and chemical interdiffusion in concentrated alloys and ionic compounds. That strategy is extended in this paper to show graphically how the vacancy-wind effect operates in interdiffusion in a stoichiometric intermetallic taking the B2 structure. A simple 4-frequency vacancy diffusion model is used. In previous work, it was shown that depending on composition and temperature, this model can exhibit the six-jump-cycle mechanism. It is shown that in the limit of perfect order that there is no vacancy-wind effect associated with this mechanism when both types of cycle operate equally (zero net vacancy flux). The non-unity value of the vacancy-wind factor found for this mechanism under zero vacancy flux conditions is purely a consequence of a particular geometric mix of tracer and collective atom displacements. The concept that a non-zero off-diagonal phenomenological coefficient provides the vacancy-wind effect is verified.
- Subject
- interdiffusion; intermetallic; six-jump-cycle mechanism; vacancy-wind effect
- Identifier
- http://hdl.handle.net/1959.13/935059
- Identifier
- uon:11956
- Identifier
- ISSN:1012-0386
- Language
- eng
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