The Contribution of Multiple Vacancies to Self‐Diffusion

Abstract

The deviations from a straight line of an Arrhenius plot of self-diffusion coefficients are discussed in terms of the contribution of multiple vacancies to self-diffusion. It is shown that for nickel the major part of the curvature may be accounted for by di-and trivacancy contributions. A small residual curvature of the Arrhenius plot is possibly indicative of a temperature dependence of the activation entropies.Xbweichungen von einem geradlinigen Verlauf in der Arrhenius-Darstellung von Selbstdiffusionskoeffizienten werden im Hinblick auf Beitrage von Mehrfachleerstellen zur Selbstdiffusion diskutiert. Es zeigt sich, daI3 bei Nickel die Kriimmung grofitenteils durch Beitrage von Doppel-und Dreifachleerstellen erklart werden kann. Die verbleibende restliche Kriimmung deutet moglicherweise auf eine Temperaturabliiingigkeit der Aktivierungsentropien hin.

Thermal analysis of lattice defects in LaNi5

“…The activation energies for migration of various types of vacancies in LaNi 5 have not been determined. However, the activation energies for migration of monovacancy, divacancy and trivacancy in Ni have been obtained to be 141, 79 and 87-97 kJ mol −1 , respectively [11]. It seems that these values in Ni are similar to those in LaNi 5 , because LaNi 5 contains 83.3 at% Ni.…”

Interpretation of Self‐Diffusion and Vacancy Properties in Gold

“…Making .the assumption that mono-and divacancies only are important and using for the total vacancy concentration at the melting point Cv(Tm) = 7.2 x [22], we estimate the fraction 2 C2v(Tm)/ C( T,) of vacant lattice sites that would be associated in divacancies a t the melting point to be 18% (for a divacancy association entropy ASzv = 0) or 46% (for ASzv = 1.5 E). Since the mobility of divacancies is larger than that of single vacancies, a divacancy binding energy as high as 0.4 eV would thus lead us to expect an appreciable contribution of divacancies to self-diffusion, which according to a detailed analysis given elsewhere [23,241 should lead to a detectable curvature in the Arrhenius plot of the self-diffusion coefficient.…”

Quenching Studies of Lattice Vacancies in High-Purity Aluminium

“…43,44) In both cases there are essentially two alternative explanations, viz. a temperature dependence of the enthalpies and entropies of formation and migration, or contributions from defects other than monovacancies.…”