Atomic Transport in Solids

Allnatt, A. R.; Lidiard, A. B.

doi:10.1017/cbo9780511563904

Cited by 406 publications

(434 citation statements)

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“…The correlation factor in Equation 1 acknowledges the possibility that a diffusing atom can jump back to its previous lattice site if the solute-vacancy pair remains un-dissociated. It can be evaluated from Lidiard's five-frequency exchange model [15,16] according to…”

Section: Discussion: Correlation Effectsmentioning

confidence: 99%

“…The interaction of substitutional solutes with vacancies in a solvent such as nickel is in fact rather complicated [15]. According to the five-frequency exchange model developed by Lidiard [15,16], five different atom-vacancy exchanges can be identified -each leading to a different local configuration of vacancy, solute and solvent atoms.…”

Section: Introductionmentioning

confidence: 99%

“…According to the five-frequency exchange model developed by Lidiard [15,16], five different atom-vacancy exchanges can be identified -each leading to a different local configuration of vacancy, solute and solvent atoms. However, to a first approximation it may be sensible to assume that the frequency Γ s of solute-vacancy exchanges controls the rate of interdiffusion, with its magnitude depending on a barrier energy E b , see Figure 3.…”

Section: Introductionmentioning

confidence: 99%

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On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

Fu¹,

Reed²,

Janotti³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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The diffusion of transition metal solutes in nickel has been studied using quantum-mechanical first principles methods, and the predictions compared critically with the experimental data available in the literature. For the 4d and 5d rows which contain Ru and Re respectively, diffusion rates are largest for elements at the far west and far east of the d-block of transition metals. The calculations reveal that this is due to a significant barrier energy for solute-vacancy exchange for elements residing at the centre of the period, e.g. Ru and Re, despite their displaying atomic sizes which are closest to that of Ni. Thus it is demonstrated conclusively that the underlying electronic bonding controls the rate of diffusion. Elements such as Ru and Re are amongst the most dense and least compressible of the transition metals due to their configuration of electrons -when alloyed with Ni this causes directional and incompressible Ni-Ru and Ni-Re bonds to be formed which hinder vacancy migration. These effects dominate over any differences in the vacancy-solute binding energy and any influence of the atomic radius of the solute. In this respect, the results disprove the traditional view that diffusion of substitutional solutes is least rapid when the size misfit with the host is the greatest. The trends for the 3d row are also studied, and it is shown that magnetism has a profound effect. Finally, if the theoretical results are to be rationalised with the experimental data, it is demonstrated that the correlation factor -which accounts for diffusional jumps in the reverse direction -should be included in the model. The results explain why some elements -for example Re -have a strong effect on the high temperature properties of the superalloys, and provide insights for future alloy design efforts.

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Section: Discussion: Correlation Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the Diffusion of Alloying Elements in the Nickel-Base Superalloys

Fu¹,

Reed²,

Janotti³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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“…(3). Assuming independent defects (low density limit) 22 the equilibrium concentration of a defect is related to its free energy of formation ∆G f according to…”

Section: A Thermodynamicsmentioning

confidence: 99%

A first-principles study of helium storage in oxides and at oxide–iron interfaces

Erhart¹

2012

Journal of Applied Physics

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Density-functional theory calculations based on conventional as well as hybrid exchange-correlation functionals have been carried out to study the properties of helium in various oxides (Al 2 O 3 , TiO 2 , Y 2 O 3 , YAP, YAG, YAM, MgO, CaO, BaO, SrO) as well as at oxide-iron interfaces. Helium interstitials in bulk oxides are shown to be energetically more favorable than substitutional helium, yet helium binds to existing vacancies. The solubility of He in oxides is systematically higher than in iron and scales with the free volume at the interstitial site nearly independently of the chemical composition of the oxide. In most oxides He migration is significantly slower and He-He binding is much weaker than in iron. To quantify the solubility of helium at oxide-iron interfaces two prototypical systems are considered (Fe|MgO, Fe|FeO|MgO). In both cases the He solubility is markedly enhanced in the interface compared to either of the bulk phases. The results of the calculations allow to construct a schematic energy landscape for He interstitials in iron. The implications of these results are discussed in the context of helium sequestration in oxide dispersion strengthened steels, including the effects of interfaces and lattice strain.

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“…Of particular technological importance is the fact that the diffusion of charged dopant atoms is strongly affected by the presence of an internal electric field [42]. As a consequence, if an inhomogeneous distribution of charged defects is present, an internal electric field is generated acting on any charged particle present in the semiconductor.…”

Section: Diffusion Studiesmentioning

confidence: 99%