| 1. |
- Boschker, J. E., et al.
(author)
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In-plane structural order of domain engineered La0.7Sr0.3MnO3 thin films
- 2013
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 93:13, s. 1549-1562
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Journal article (peer-reviewed)abstract
- We present a detailed structural study of tensile-strained La0.7Sr0.3MnO3 thin films. We use the substrate miscut to control the number of rhombohedral variants in the films and study the in-plane order and structural distortions. Using high-resolution X-ray diffraction, we demonstrate that step-edge induced lattice modulations occur in 4-variant films, whereas periodic twinning is the dominant in-plane order for 2-variant films. We show that the in-plane twinning angle is almost completely relaxed. However, the relaxation of shear strain by the out-of-plane twinning angle and the monoclinic distortion is only partial. Furthermore, the film thickness dependence of the domain width reveals that domain formation is a universal mechanism for shear strain relaxation. Finally, we show that the structural response to the transition from the paramagnetic to the ferromagnetic phase of La0.7Sr0.3MnO3 at 345K is smaller in 4-variant films compared to 2-variant films.
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| 2. |
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| 3. |
- Sandberg, Nils, et al.
(author)
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Ab initio simulations of clustering and precipitation in Al-Mg-Si alloys
- 2007
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In: Computational Materials Science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 40:3, s. 309-318
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Journal article (peer-reviewed)abstract
- A class of proposed coherent precipitate structures (Guinier-Preston zones) in the Al-Mg-Si alloy are investigated using first-prin- ciples density functional theory methods. The cluster expansion method is used to extract effective interaction parameters, providing the means for large scale energy calculations of alloy structures. The Mg1Si1 L1(0) structure and structures related to the Mg5Si6 beta '' phase are studied in more detail, and e.g., precipitate/matrix interface energies are presented. Using direct first-principles calculations we show that the former phase is dynamically unstable and thus must be stabilized by the surrounding Al matrix. Monte Carlo simulations and free-energy techniques are used to study the Al rich side of the phase diagram with the current CE parameters, and kinetic Monte Carlo simulations are used to study clustering in the disordered phase. The implications of our findings are discussed in the framework of classical nucleation theories, and we outline possible nucleation mechanisms. (C) 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Sandberg, Nils, et al.
(author)
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First-principles calculations of impurity diffusion activation energies in Al
- 2006
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:1
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Journal article (peer-reviewed)abstract
- We present first-principles density functional theory calculations of the diffusion activation energies of Mg, Si, and the 3d transition metals Sc-Zn in Al. In general, the calculated activation energies are underestimated with respect to experiments by 5-25%. The trend seen in experiments, namely, that impurities around Ti, V, and Cr have high diffusion activation energies leading to "anomalously" slow diffusion, is well reproduced in the present calculations. We provide an explanation in terms of electrostatic screening effects.
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