It was noted that the rate theory of irradiation effects in crystalline solids rested on a set of 2 ordinary differential equations which, for each type of point defect (vacancy, self-interstitial), described the balance between the production of defects and their annihilation. The latter process occurred either via mutual recombination, bimolecular reaction or elimination at point defect sinks; a first-order reaction. The elimination rate was proportional to the defect concentration multiplied by the defect diffusion coefficient and a geometrical factor termed the so-called sink strength. The classical expression for sink strengths was obtained by solving the diffusion equation for point defects in a cell which contained the sink, and ensuring that the mean value of the defect concentration in the cell equaled the concentration in the rate theory. An alternative criterion was proposed here. Since the amplitude of the irradiation effects of practical interest was dictated by the partitioning of the defect annihilation between mutual recombination and elimination at sinks, it was suggested that the value of the sink strength should give the correct value for the latter partitioning. The sink strengths thus defined, scaled to their classical value, were evaluated for sink geometries of practical interest and were expressed as a function of a single dimensionless parameter which was a function of the irradiation flux

temperature. Depending upon the irradiation conditions, the correcting factors for individual sink strengths could be large (several orders of magnitude). When several types of sinks competed, it was further supposed that the partitioning of the elimination among the various types of sink had the correct value. The present sink strengths were additive; unlike the classical ones. According to the present definition, the dislocation bias (which measured the relative difference between the sink strengths of dislocations for interstitials and vacancies), was shown to increase with the strength of neutral sinks around the dislocation. It ranged from zero, when the dislocations were the only sinks, to several 10–1 when the neutral sinks had a strength that was much larger than that of dislocations. The calculation of the correcting factor could be easily incorporated into the rate theory of irradiation effects.

Elimination of Irradiation Point Defects in Crystalline Solids - Sink Strengths. N.V.Doan, G.Martin: Physical Review B, 2003, 67[13], 134107 (11pp)

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