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  • AIP Publishing  (6)
  • 1
    Online Resource
    Online Resource
    Influence of chemistry and structure on interfacial segregation in NbMoTaW with high-throughput atomistic simulations
    AIP Publishing ; 2022
    In:  Journal of Applied Physics Vol. 132, No. 23 ( 2022-12-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 132, No. 23 ( 2022-12-21)
    Abstract: Refractory multi-principal element alloys exhibiting promising mechanical properties such as excellent strength retention at elevated temperatures have been attracting increasing attention. Although their inherent chemical complexity is considered a defining feature, a challenge arises in predicting local chemical ordering, particularly in grain boundary regions with an enhanced structural disorder. In this study, we use atomistic simulations of a large group of bicrystal models to sample a wide variety of interfacial sites (grain boundary) in NbMoTaW and explore emergent trends in interfacial segregation and the underlying structural and chemical driving factors. Sampling hundreds of bicrystals along the [001] symmetric tilt axis and analyzing more than one hundred and thirty thousand grain boundary sites with a variety of local atomic environments, we uncover segregation trends in NbMoTaW. While Nb is the dominant segregant, more notable are the segregation patterns that deviate from expected behavior and mark situations where local structural and chemical driving forces lead to interesting segregation events. For example, incomplete depletion of Ta in low-angle boundaries results from chemical pinning due to favorable local compositional environments associated with chemical short-range ordering. Finally, machine learning models capturing and comparing the structural and chemical features of interfacial sites are developed to weigh their relative importance and contributions to segregation tendency, revealing a significant increase in predictive capability when including local chemical information. Overall, this work, highlighting the complex interplay between the local grain boundary structure and chemical short-range ordering, suggests tunable segregation and chemical ordering by tailoring grain boundary structure in multi-principal element alloys.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0130402
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
    Online Resource
    Online Resource
    Strength softening mitigation in bimodal structured metals
    AIP Publishing ; 2022
    In:  Journal of Applied Physics Vol. 131, No. 4 ( 2022-01-31)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 131, No. 4 ( 2022-01-31)
    Abstract: Polycrystalline metals become stronger with a decrease in the constitute grain size, yet strength softening takes over at the nanometer regime. Here, we find that this softening rate can be tailored and mitigated by tuning structural heterogeneity and grain size uniformity. With reducing the small grain size in bimodal structures, the strength reduction is markedly alleviated due to the enhanced strengthening of large grains. This mitigation of strength softening is mediated by promoted intragranular slip, extra dislocation storage, and reduced grain boundary sliding in bimodal structures. Our findings signifying the role of grain size non-uniformity on crystal plasticity shed light on a broad class of heterogeneous structured materials with improved strength and ductility.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0075475
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
    Online Resource
    Online Resource
    Strain rate-dependent tensile response of glassy silicon nanowires studied by accelerated atomistic simulations
    AIP Publishing ; 2021
    In:  Journal of Applied Physics Vol. 130, No. 8 ( 2021-08-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 130, No. 8 ( 2021-08-28)
    Abstract: Mechanical properties of glassy nanowires have been intensively investigated recently by both nanomechanical experiments and atomic-level simulations. Unfortunately, there exists a huge gap in the strain rate of the nanomechanical tests between experiments and simulations, which makes it difficult to compare results even for the same material system. Using accelerated atomistic simulations based on a self-learning metabasin escape algorithm, here, we report the tensile mechanical properties of amorphous Stillinger–Weber silicon nanowires with different intrinsic ductility under strain rates ranging from 1010 to 10−1 s−1. It is found that both brittle and ductile glassy silicon nanowires display weakened strength with a decreasing strain rate, in agreement with the cooperative shear model. Moreover, as the strain rate decreases, the amount of plasticity remains unchanged for the brittle nanowires, yet it decreases for the ductile ones. Such deteriorated plasticity in ductile glassy nanowires is caused by enhanced strain localization at low strain rates. Lastly, we show that via the distance matrix of nonaffine displacement, a more hierarchical potential energy landscape is responsible for the higher strain localization propensity in ductile silicon glassy nanowires.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0060136
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 4
    Online Resource
    Online Resource
    Dislocation mechanisms in strengthening and softening of nanotwinned materials
    AIP Publishing ; 2023
    In:  Journal of Applied Physics Vol. 133, No. 5 ( 2023-02-07)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 133, No. 5 ( 2023-02-07)
    Abstract: Twin boundary (TB) strengthening in nanotwinned metals experiences a breakdown below a critical spacing at which softening takes over. Here, we survey a range of nanotwinned materials that possess different stacking fault energies (SFEs) and understand the TB strengthening limit using atomistic simulations. Distinct from Cu and Al, the nanotwinned, ultralow SFE materials (Co, NiCoCr, and NiCoCrFeMn) intriguingly exhibit a continuous strengthening down to a twin thickness of 0.63 nm. Examining dislocation slip mode and deformation microstructure, we find the hard dislocation modes persist even when reducing the twin boundary spacing to a nanometer regime. Meanwhile, the soft dislocation mode, which causes detwinning in Cu and Al, results in phase transformation and lamellar structure formation in Co, NiCoCr, and NiCoCrFeMn. This study, providing an enhanced understanding of dislocation mechanism in nanotwinned materials, demonstrates the potential for controlling mechanical behavior and ultimate strength with broadly tunable composition and SFE, especially in multi-principal element alloys.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0138379
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 5
    Online Resource
    Online Resource
    Density functional theory calculation of edge stresses in monolayer MoS2
    AIP Publishing ; 2013
    In:  Journal of Applied Physics Vol. 114, No. 16 ( 2013-10-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 114, No. 16 ( 2013-10-28)
    Abstract: We utilize density functional theory to calculate the edge energy and edge stress for monolayer MoS2 nanoribbons. In contrast to previous reports for graphene, for both armchair and zigzag chiralities, the edge stresses for MoS2 nanoribbons are found to be tensile, indicating that their lowest energy configuration is one of compression in which Mo-S bond lengths are shorter than those in a bulk, periodic MoS2 monolayer. The edge energy and edge stress is found to converge for both chiralities for nanoribbon widths larger than about 1 nm.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4826905
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    Online Resource
    Online Resource
    β -sheet-like formation during the mechanical unfolding of prion protein
    AIP Publishing ; 2015
    In:  The Journal of Chemical Physics Vol. 143, No. 12 ( 2015-09-28)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 143, No. 12 ( 2015-09-28)
    Abstract: Single molecule experiments and simulations have been widely used to characterize the unfolding and folding pathways of different proteins. However, with few exceptions, these tools have not been applied to study prion protein, PrPC, whose misfolded form PrPSc can induce a group of fatal neurodegenerative diseases. Here, we apply novel atomistic modeling based on potential energy surface exploration to study the constant force unfolding of human PrP at time scales inaccessible with standard molecular dynamics. We demonstrate for forces around 100 pN, prion forms a stable, three-stranded β-sheet-like intermediate configuration containing residues 155-214 with a lifetime exceeding hundreds of nanoseconds. A mutant without the disulfide bridge shows lower stability during the unfolding process but still forms the three-stranded structure. The simulations thus not only show the atomistic details of the mechanically induced structural conversion from the native α-helical structure to the β-rich-like form but also lend support to the structural theory that there is a core of the recombinant PrP amyloid, a misfolded form reported to induce transmissible disease, mapping to C-terminal residues ≈160-220.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.4931819
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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