CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such a...CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such as irradiation,severe plastic deformation,and hydrogen embrittlement.These loops,more intricate than simple dislocations,exhibit far more intricate reaction and evolution pathways arising from the loop type transformation and the associated planar fault transition.This can significantly alter dislocation activities contributing to dislocation channels and complex dislocation networks,which are closely linked to crack initiation and propagation during fracture.Understanding the transformation of DLs is crucial for the development of materials capable of withstanding harsh environments,including those encountered in nuclear reactors,aerospace applications,and hydrogen-rich environments.This Account delves into the computational advancements in studying DL transformations in FCC,HCP,and BCC metals.Traditional simulations often struggle to capture the complexity of DL structures and interactions.To overcome these limitations,a novel computational approach has been developed,enabling precise construction and analysis of DLs.Not only does it automatically account for necessary atom addition or deletion,it is also generic and versatile,applicable for any arbitrary DL morphology with planar fault or fault combination in both pristine metal and complex alloy systems.The new construction approach of DLs provides a critical enabler for studying the transformation of DLs across different crystal structures.In high-symmetry FCC metals,these transformations involve complex unfaulting driven by Shockley and Frank loop interactions,influenced by variations in stress,temperature,and radiation.Meanwhile,HCP metals,with a lower crystal symmetry,exhibit more complex DL transformations due to high anisotropy in the slip systems,variation in Burgers vectors,and different planar faults.Unlike pristine FCC and HCP lattices,ordered intermetallic systems like L12-Ni3Al experience a disruption of translational symmetry within the lattice.The ordered nature of these alloys complicates DL interacting with line dislocation,causing asymmetrical shearing and looping mechanisms.BCC metals,in contrast,exhibit different DL evolution due to the lack of stable stacking faults,leading to stronger interactions with impurities such as carbon and hydrogen.In particular,the interaction between DLs and hydrogen in BCC metals is a critical aspect worth investigating as it can cause severe damage in BCC materials under irradiation,hydrogen embrittlement,and intense deformation.This Account highlights the complex nature of DL transformation in metals under extreme environments and recent computational advances.Differences in the evolution of DLs across crystal structures and their interactions with cracks and solute elements are critical areas for future research.Key challenges include extending DL transformation theories to ordered lattice structures,developing machine-learning-based interatomic potentials,and refining multiscale models to better capture the dynamic behavior of DLs.These efforts will help develop more accurate predictive models,leading to materials with improved resistance to deformation and fracture in harsh environments.展开更多
Phylogenomic analysis of whole genome sequences of five benzylisoquinoline alkaloid(BIA)-producing species from the Ranunculales and Proteales orders of flowering plants revealed the sequence and timing of evolutionar...Phylogenomic analysis of whole genome sequences of five benzylisoquinoline alkaloid(BIA)-producing species from the Ranunculales and Proteales orders of flowering plants revealed the sequence and timing of evolutionary events leading to the diversification of these compounds.(S)-Reticuline is a pivotal intermediate in the synthesis of many BIAs and our analyses revealed parallel evolution between the two orders,which diverged122 million years ago(MYA).Berberine is present in species across the entire Ranunculales,and we found co-evolution of genes essential for production of the protoberberine class.The benzophenanthridine class,which includes the antimicrobial compound sanguinarine,is specific to the Papaveraceae family of Ranunculales,and biosynthetic genes emerged after the split with the Ranunculaceae family110 MYA but before the split of the three Papaveraceae species used in this study at77 MYA.The phthalideisoquinoline noscapine and morphinan class of BIAs are exclusive to the opium poppy lineage.Ks estimation of paralogous pairs indicates that morphine biosynthesis evolved more recently than 18 MYA in the Papaver genus.In the preceding 100 million years gene duplication,neofunctionalization and recruitment of additional enzyme classes,combined with gene clustering,gene fusion,and gene amplification,resulted in emergence of medicinally valuable BIAs including morphine and noscapine.展开更多
基金the financial support from National Natural Science Foundation of China(NSFC Grants No.12002277 and No.52401010)Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery grant(RGPIN-2023-03628)McGill’s William Dawson Scholar fund.
文摘CONSPECTUS:Dislocation loops(DLs),characterized by closed dislocation lines,are a category of defects of vital importance in determining the mechanical properties of metals,particularly under extreme conditions,such as irradiation,severe plastic deformation,and hydrogen embrittlement.These loops,more intricate than simple dislocations,exhibit far more intricate reaction and evolution pathways arising from the loop type transformation and the associated planar fault transition.This can significantly alter dislocation activities contributing to dislocation channels and complex dislocation networks,which are closely linked to crack initiation and propagation during fracture.Understanding the transformation of DLs is crucial for the development of materials capable of withstanding harsh environments,including those encountered in nuclear reactors,aerospace applications,and hydrogen-rich environments.This Account delves into the computational advancements in studying DL transformations in FCC,HCP,and BCC metals.Traditional simulations often struggle to capture the complexity of DL structures and interactions.To overcome these limitations,a novel computational approach has been developed,enabling precise construction and analysis of DLs.Not only does it automatically account for necessary atom addition or deletion,it is also generic and versatile,applicable for any arbitrary DL morphology with planar fault or fault combination in both pristine metal and complex alloy systems.The new construction approach of DLs provides a critical enabler for studying the transformation of DLs across different crystal structures.In high-symmetry FCC metals,these transformations involve complex unfaulting driven by Shockley and Frank loop interactions,influenced by variations in stress,temperature,and radiation.Meanwhile,HCP metals,with a lower crystal symmetry,exhibit more complex DL transformations due to high anisotropy in the slip systems,variation in Burgers vectors,and different planar faults.Unlike pristine FCC and HCP lattices,ordered intermetallic systems like L12-Ni3Al experience a disruption of translational symmetry within the lattice.The ordered nature of these alloys complicates DL interacting with line dislocation,causing asymmetrical shearing and looping mechanisms.BCC metals,in contrast,exhibit different DL evolution due to the lack of stable stacking faults,leading to stronger interactions with impurities such as carbon and hydrogen.In particular,the interaction between DLs and hydrogen in BCC metals is a critical aspect worth investigating as it can cause severe damage in BCC materials under irradiation,hydrogen embrittlement,and intense deformation.This Account highlights the complex nature of DL transformation in metals under extreme environments and recent computational advances.Differences in the evolution of DLs across crystal structures and their interactions with cracks and solute elements are critical areas for future research.Key challenges include extending DL transformation theories to ordered lattice structures,developing machine-learning-based interatomic potentials,and refining multiscale models to better capture the dynamic behavior of DLs.These efforts will help develop more accurate predictive models,leading to materials with improved resistance to deformation and fracture in harsh environments.
基金I.A.G.received support from the Biotechnology and Biological Sciences Research Council,United Kingdom(grant BB/K018809/1)and the Gar-field Weston Foundation,United Kingdom.
文摘Phylogenomic analysis of whole genome sequences of five benzylisoquinoline alkaloid(BIA)-producing species from the Ranunculales and Proteales orders of flowering plants revealed the sequence and timing of evolutionary events leading to the diversification of these compounds.(S)-Reticuline is a pivotal intermediate in the synthesis of many BIAs and our analyses revealed parallel evolution between the two orders,which diverged122 million years ago(MYA).Berberine is present in species across the entire Ranunculales,and we found co-evolution of genes essential for production of the protoberberine class.The benzophenanthridine class,which includes the antimicrobial compound sanguinarine,is specific to the Papaveraceae family of Ranunculales,and biosynthetic genes emerged after the split with the Ranunculaceae family110 MYA but before the split of the three Papaveraceae species used in this study at77 MYA.The phthalideisoquinoline noscapine and morphinan class of BIAs are exclusive to the opium poppy lineage.Ks estimation of paralogous pairs indicates that morphine biosynthesis evolved more recently than 18 MYA in the Papaver genus.In the preceding 100 million years gene duplication,neofunctionalization and recruitment of additional enzyme classes,combined with gene clustering,gene fusion,and gene amplification,resulted in emergence of medicinally valuable BIAs including morphine and noscapine.
