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- Toijer, Elin, et al.
(författare)
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Ab initio modelling of intergranular fracture of nickel containing phosphorus : Interfacial excess properties
- 2021
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Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the impact of phosphorus impurities on the grain boundary strength of nickel has been investigated by means of density functional theory (DFT) modelling. Owing to different outcomes and trends previously reported in the literature, it is unclear whether P is strengthening or weakening the Ni grain boundary. To address this issue, we utilize three different DFT based methods: the excess-energy approach, rigid grain separation, and Rice-Wang's thermodynamic approach. The results show that the commonly used rigid model predicts P to have an increasing effect on the peak stress of Ni of up to 14%, as opposed to a reduction, which is indicated by the excess-energy approach. Employment of the Rice-Wang approach, on the other hand, displays a slight reduction in work of separation. The results show that the discrepancies between previous works can be attributed not so much to the physics of the system, but to the applied model, the partition scheme and the interpretation of the outcomes. This underlines the importance of a proper description of the fracture process, and shows that common simplifications can have a decisive impact on the observed trends.
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| 2. |
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| 3. |
- Mirzai, Amin, et al.
(författare)
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First-principle investigation of doping effects on mechanical and thermodynamic properties of Y2SiO5
- 2021
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Ingår i: Mechanics of materials. - : Elsevier. - 0167-6636 .- 1872-7743. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the variation of elastic stiffness moduli and the thermodynamic properties of yttrium orthosilicate (Y2SiO5, YSO) under various doping concentrations of Eu3+ ions. The model is based on a low temperature approximation (T « θD), and the plane-wave density functional theory (DFT) is used to carry out the calculations. The results show that the ions primarily occupy the Y1 site of the basic molecule for all applied concentrations. The overall shear, bulk, and Young’s moduli exhibit a decreasing trend with increasing concentration. The overall anisotropy shows a very small increase with increasing concentration. The Debye temperature as well as the Grünesien parameter for each concentration are predicted. Lastly, the predicted heat capacity at constant volume is calculated and compared to experimental values. Our study reveals that there is almost linear relationship between concentration and mechanical properties of YSO. The decrease of the Grünesien parameter with concentration increase might decrease the anharmonic effects in YSO, although this effect is small. In addition, the change in heat capacity with concentration rise is negligible.
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| 4. |
- Olsson, Pär A T, 1981-, et al.
(författare)
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Atomistic investigation of functionalized polyethylene-alumina interfacial strength and tensile behaviour
- 2021
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Ingår i: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 187
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Tidskriftsartikel (refereegranskat)abstract
- We study the adhesion and tensile behaviour of bi-layer interfaces comprising polyethylene, doped with carbonyl and hydroxyl functional groups emanating from ozone treatment, and α" role="presentation">-Al2O3" role="presentation"> by means of density functional theory and classical atomistic modelling. The results show that the deformations are localized within the polymer and comprise chain slip, disentanglement and detachment from the substrate, where only the latter is notably affected by the doping. The binding energies and excess forces associated with the detachment of functional groups from the alumina substrate are of the order of 1.7 eV and 1 nN, respectively, for both types. Although such forces do not affect the maximum peak stress notably, they give rise to spikes in the traction-separation curves following the fibril formation and promote increased total work of fracture.
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