Hydrogen sorption capacity of crystal lattice defects and low Miller index surfaces of copper

Lousada, Cláudio M.; Korzhavyi, Pavel A.

doi:10.1007/s10853-020-04459-z

Cited by 14 publications

(22 citation statements)

References 49 publications

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“…We have chosen this GB because it occurs frequently in fcc Cu [16][17][18] and it has a geometry with a diverse openness due to sites with different coordination numbers and local volume at the GB plane. In a previous work we have shown that the volume expansion is a key parameter for driving the segregation of dopants to GBs [1,7]. The GB model of Figure 1 was constructed using the coincidence-site lattice (CSL) method and a periodic supercell that contains two oppositely oriented Σ9 GBs.…”

Section: Figurementioning

confidence: 99%

“…We have shown previously that for fcc Cu the Σ5 and Σ11 GBs can increase the strength of the segregation of substitutional impurities at certain atomic sites while the Σ3 GB has no ability to trigger the segregation of impurities [7]. The dominating effect is the volume expansion at certain GB sites of the Σ5 and Σ11 and because the Σ3 has no sites with considerable volume expansion, the segregation of impurities from the bulk is not favorable [1,7].…”

Section: Introductionmentioning

confidence: 98%

“…The binding energy of substitutional and interstitial impurities to grain boundaries (GBs) is highly dependent of the local structure of the GBs [1,2]. This is because at many GB the local atomic environment differs considerably when compared to the bulk [3].…”

Section: Introductionmentioning

confidence: 99%

“…This is because at many GB the local atomic environment differs considerably when compared to the bulk [3]. These features have an important direct impact on several local properties of the material at the GBs, such as segregation of impurities, defect mobility and grain boundary sink efficiency [1,4,5]. For some materials, such local GB features can affect the microcrystallinity [6] and other global properties, such as creep [7], plasticity, strength and can also affect hydrogen embrittlement and stress corrosion cracking mechanisms [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Our previous investigations on the segregation of P and S at low index symmetric tilt GBs of Cu-Σ3, Σ5 and Σ11-have shown a large variation in the segregation energies (∆E seg ) for these elements both as a function of GB type and as a function of the distance from the GB plane [7]. However, the Σ3, Σ5 and Σ11 GBs have as a common feature, the fact that within their GB planes, the coordination, geometry and local volume for copper atoms and interstitial sites is fairly homogeneous and considerable variations in these features occur only as a function of distance from the GB plane [1]. In order to understand if the ∆E seg can also vary considerably within GB planes it is important to study other GBs with a more diverse local atomic environment within GB plane.…”

Section: Introductionmentioning

confidence: 99%

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Segregation of P and S Impurities to A Σ9 Grain Boundary in Cu

Lousada

Korzhavyi

2020

Metals

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The segregation of P and S to grain boundaries (GBs) in fcc Cu has implications in diverse physical-chemical properties of the material and this can be of particular high relevance when the material is employed in high performance applications. Here, we studied the segregation of P and S to the symmetric tilt Σ9 (22¯1¯) [110], 38.9° GB of fcc Cu. This GB is characterized by a variety of segregation sites within and near the GB plane, with considerable differences in both atomic site volume and coordination number and geometry. We found that the segregation energies of P and S vary considerably both with distance from the GB plane and sites within the GB plane. The segregation energy is significantly large at the GB plane but drops to almost zero at a distance of only ≈3.5 Å from this. Additionally, for each impurity there are considerable variations in energy (up to 0.6 eV) between segregation sites in the GB plane. These variations have origins both in differences in coordination number and atomic site volume with the effect of coordination number dominating. For sites with the same coordination number, up to a certain atomic site volume, a larger atomic site volume leads to a stronger segregation. After that limit in volume has been reached, a larger volume leads to weaker segregation. The fact that the segregation energy varies with such magnitude within the Σ9 GB plane may have implications in the accumulation of these impurities at these GBs in the material. Because of this, atomic-scale variations of concentration of P and S are expected to occur at the Σ9 GB center and in other GBs with similar features.

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Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Segregation of P and S Impurities to A Σ9 Grain Boundary in Cu

Lousada

Korzhavyi

2020

Metals

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Pathways of hydrogen atom diffusion at fcc Cu: Σ9 and Σ5 grain boundaries vs single crystal

Lousada,

Korzhavyi

2023

J Mater Sci

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The diffusion of H-atoms is relevant for innumerous physical–chemical processes in metals. A detailed understanding of diffusion in a polycrystalline material requires the knowledge of the activation energies (ΔEa’s) for diffusion at different defects. Here, we report a study of the diffusion of H-atoms at the Σ9 and Σ5 grain boundaries (GBs) of fcc Cu that are relevant for practical applications of the material. The complete set of possible diffusion pathways was determined for each GB and we compared the ΔEa at bulk fcc Cu with the landscape of ΔEa’s at these defects. We found that while a number of diffusion pathways at the GBs have high tortuosity, there are also many paths with very low tortuosity because of specific structural features of the interstitial GB sites. These data show that the diffusion of H-atoms at these GBs is highly directional but can be fast because at certain paths the ΔEa can be as low as 0.05 eV. The lowest energy paths for diffusion of H-atoms through the whole GB models are ΔEa = 0.05 eV for the Σ9 and ΔEa = 0.20 eV at Σ5 which compare with ΔEa = 0.42 eV for the bulk fcc crystal. This shows that H-atoms will be able to diffuse very fast at these defects. With the Laguerre–Voronoi tessellation method, we studied how the local atomic structure of the interstitial sites of the GBs leads to different ΔEa’s for diffusion of H-atoms. We found that the volume expansions and the coordination numbers alone cannot account for the magnitude of the ΔEa’s. Hence, we developed a symmetry quantifying parameter that measures the deviation of symmetry of the GB sites from that of the bulk octahedral site and hence accounts for the distortion at the GB site. Only when this parameter is introduced together with the volume expansions and the coordination numbers, it is possible to correlate the local structure with the ΔEa’s and to obtain descriptors of diffusion. The complete set of data shows that the extrapolation of diffusion data for H-atoms between different types of GBs is non-trivial and should be done with care.

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