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Deep learning approach to genome of two-dimensional materials with flat electronic bands

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npj Computational Materials 2023年第1期9卷 1316-1324页

作者： A.Bhattacharya I.Timokhin R.Chatterjee q.yang A.Mishchenko Department of Physics and Astronomy University of ManchesterManchesterUK Department of Mechanical Engineering Indian Institute of Technology DelhiNew DelhiIndia Department of Physics Indian Institute of Technology DelhiNew DelhiIndia

Electron-electron correlations play central role in condensed matter physics,governing phenomena from superconductivity to magnetism and numerous technological applications.Two-dimensional(2D)materials with flat electronic bands provide natural playground to explore interaction-driven physics,thanks to their highly localized electrons.The search for 2D flat band materials has attracted intensive efforts,especially now with open science databases encompassing thousands of materials with computed electronic bands.Here we automate the otherwise daunting task of materials search and classification by combining supervised and unsupervised machine learning algorithms.To this end,convolutional neural network was employed to identify 2D flat band materials,which were then subjected to symmetry-based analysis using a bilayer unsupervised learning algorithm.Such hybrid approach of exploring materials databases allowed us to construct a genome of 2D materials hosting flat bands and to reveal material classes outside the known flat band paradigms.

关键词： Deep electronic approach

Enhancing strength and ductility of AlSi10Mg fabricated by selective laser melting by TiB_(2)nanoparticles

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Journal of Materials Science & Technology 2022年第14期109卷 254-266页

作者： Y.K.Xiao H.Chen Z.Y.Bian T.T.Sun H.Ding q.yang Y.Wu q.Lian Z.Chen H.W.Wang State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240China School of Materials Science&Engineering Shanghai Jiao Tong UniversityShanghai 200240China

In the metallic components fabricated by the emerging selective laser melting(SLM)technology,most strategies used for strengthening the materials sacrifice the ductility,leading to the so-called strengthductility trade-off.In the present study,we report that the strength and ductility of materials can be enhanced simultaneously by introducing nanoparticles,which can break the trade-off of the metallic materials.In the case of in-situ nano-TiB_(2)decorated AlSi10Mg composites,the introduced nanoparticles lead to columnar-to-equiaxed transition,grain refinement and texture elimination.With increasing content of nanoparticles,the strength increases continually.Significantly,the ductility first increases and then decreases.Our results show that the ductility is controlled by the competition between the crack-induced catastrophic fracture and ductile fracture associated with dislocation activities.The first increase of ductility is mainly attributed to the suppression of crack-induced catastrophic fracture when TiB_(2)nanoparticles present.With the further increase of TiB_(2)nanoparticles,the subsequent decrease of ductility is mainly controlled by dislocation activities.Thus,the materials will exhibit the optimum strength and ductility combination in a certain range of TiB_(2)nanoparticles.This study clarifies the physical mechanism controlling ductility for nano-TiB_(2)decorated Al Si10Mg composites,which provides the insights for the design of structural materials.

关键词： Selective laser melting Aluminium matrix composites Ductility Mechanical behavior Dislocations Cracks

Influencing mechanism of pre-existing nanoscale Al5Fe2 phase on Mg-Fe interface in friction stir spot welded Al-free ZK60-q235 joint

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Journal of Materials Science & Technology 2020年第7期42卷 220-228页

作者： R.Z.Xu q.yang D.R.Ni B.L.Xiao C.Z.Liu Z.Y.Ma Institute of Metal Research Chinese Academy of SciencesShenyang110016China College of Material Science and Engineering Shenyang Aerospace UniversityShenyang110136China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign1304 W Green StUrbanaIL61801United States Fredrick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign104 S Goodwin AveUrbanaIL61801United States

Al-free ZK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of ZK60 Mg alloy and q235 steel with a hot-dipped aluminum (Al)-containing zinc (Zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed during FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the ZK60-steel joint could reach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.

关键词： Dissimilar welding Friction stir spot welding Magnesium alloys Steels Zinc coating

Pinless Friction Stir Spot Welding of Mg-3Al-1Zn Alloy with Zn Interlayer

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Journal of Materials Science & Technology 2016年第1期32卷 76-88页

作者： R.Z.Xu D.R.Ni q.yang C.Z.Liu Z.Y.Ma College of Materials Science and Engineering Shenyang Aerospace University Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

With the addition of a thin Zn interlayer, 2.4 mm thick Mg-3AI-1Zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive （α-Mg ＋ MgZn） eutectic structure under- neath the shoulder and a Mg-Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSWjoints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg-Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths re- sulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the fiat shoul- der. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.

关键词： Friction stir spot welding Magnesium alloys Zn interlayer Hook defects

Knock in p53 sequences with and without intron 4 to determine its function in gene expression control

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Chinese Medical Journal 1999年第11期112卷 22-22页

作者： q.yang Z-q.Wang M.Hollstein German Canc Res Ctr Div Toxicol & Canc Risk Factors D-69120 Heidelberg Germany Int Agcy Res Canc Unit Gene Environm Interact F-69372 Lyon France

MHD Instabilities and Their Effects on Plasma Confinement in Large Helical Device Plasmas with Intense Neutral Beam Injection

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Plasma Science and Technology 2004年第3期6卷 2269-2274页

作者： K.Toi S.Ohdachi S.Yamamoto S.Sakakibara K.Y.Watanabe N.Nakajima X.Ding J.Li S.Morita K.Narihara K.Tanaka T.Tokuzawa H.Yamada q.yang National Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanDep. Energy Eng. Sci. Nagoya Univ. Nagoya 464-8603 JapanNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanSouthestern Institute of Physics Chengdu ChinaInstitute of Plasma Physics Chinese Academy of Science ChinaNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanNational Institute for Fusion Science Toki 509-5292 JapanSouthestern Institute of Physics Chengdu China

MHD stability of the Large Helical Device (LHD) plasmas produced with intenseneutral beam injection is experimentally studied. When the steep pressure gradient near the edge isproduced through L-H transition or linear density ramp experiment, interchange-like MHD modes whoserational surface is located very close to the last closed flux surface are strongly excited in acertain discharge condition and affect the plasma transport appreciably. In NBI-heated plasmasproduced at low toroidal field, various Alfven eigenmodes are often excited. Bursting toroidalAlfven egenmodes excited by the presence of energetic ions induce appreciable amount of energeticion loss, but also trigger the formation of internal and edge transport barriers.

关键词： interchange instabilities L-H transition alfven eigenmodes

格陵兰冰芯记录的大气环流变化及其与南极冰芯的比较(英)

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冰川冻土 1998年第4期20卷 398-407页

作者： P.A.Mayewski L.D.Meeker M.S.Twickler S.Whitlow q.yang K.Kreutz D.Reusch University of New Hampshire 美国

The GISP2, central Greealand, glaciochemical series (sodium, potassium, ammonium,calcium, magnesium, sulfate, nitrate and chloride) provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over much of the Northern Hemisphere. Interpretation of this record reveals the controls on both high and low frequency climate events of the last 110 000 years.Changes in insolation on the order of the major orbital cycles control the long-term behavior of atmospheric circulation patterns through changes in ice volume (sea level) and related positive feedbacks.Events such as the Heinrich events (massive discharges of icebergs first identified in the marine record)are found to operate on a 6 100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics Rapid climate change events (massive reorganizations of atmospheric circulation) are demonstrated to operate on 1 450 year cycle possibly in response to internal oscillations in the ocean-atmosphere system or due to changes in solar output. Changes in insolation and associated positive feedbacks related to ice sheets assist in explaining favorable time periods and controls on the amplitude of these massive rapid climate change events.Comparison of the GISP2 glaciochemical series with an ice record from Taylor Dome in Antarctica indicates considerable similarity suggesting that both polar regions experience marked changes in climate. While preliminary evidence points to similar phasing of several major climate events in the two polar regions exact phasing cannot as yet be determined, because dating of Antarctic ice core records is not as well-established as the dating for Greenland ice cores.

关键词：古气候大气环流变化南极冰芯格陵兰冰芯

Oxygen vacancies in ferroelectric perovskites and their regulation from first-principles study

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Oxygen vacancies in ferroelectric perovskites and their regu...

Suppression of ferroelectric fatigue introduced by oxygen vacancies in tetragonal PbTiO3 through misfit strain:A first principle study

第十三届全国物理力学学术会议

作者： q.yang J.X.Cao Y.C.Zhou Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education Xiangtan University

Oxygen vacancy(VO)is one of the common and mobile defects,which is believed to play an important role in the electrical properties of ferroelectric materials.In present work,the physical properties of VO were studied with a prototypical ferroelectric perovskite oxide Pt Ti O3(PTO)using density functional theory(DFT)calculation.Meanwhile,we studied the effects of potential regulation means,such as epitaxial strain,on the structural and electronic properties of VO.VO was found to result in a tail-to-tail domain configuration and pinning the domain wall movement.Our results show that VO in ferroelectric epitaxial thin films can be systematically tuned from a strong domain-pinning centre to a non-pinning centre by applying a compressive misfit strain.The formation and migration energies of VO can be enhanced by compressive strain.This suggests that proper strain may solve the VO-induced ferroelectric failure.

关键词： Ferroelectric perovskites Oxygen vacancies Domain-pinning centre Leakage current First-principles study

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Suppression of ferroelectric fatigue introduced by oxygen va...