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MAGUS: machine learning and graph theory assisted universal structure searcher

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national Science Review 2023年第7期10卷 213-233页

作者： Junjie Wang Hao Gao Yu Han Chi Ding Shuning Pan Yong Wang Qiuhan Jia Hui-Tian Wang Dingyu Xing Jian Sun national laboratory of solid state microstructures School of Physics and Collaborative Innovation Center of Advanced Microstructures Nanjing University

Crystal structure predictions based on first-principles calculations have gained great success in materials science and solid state ***,the remaining challenges still limit their applications in systems with a large number of atoms,especially the complexity of conformational space and the cost of local optimizations for big ***,we introduce a crystal structure prediction method,MAGUS,based on the evolutionary algorithm,which addresses the above challenges with machine learning and graph *** used in the program are summarized in detail and benchmark tests are *** intensive tests,we demonstrate that on-the-fly machine-learning potentials can be used to significantly reduce the number of expensive first-principles calculations,and the crystal decomposition based on graph theory can efficiently decrease the required configurations in order to find the target *** also summarized the representative applications of this method on several research topics,including unexpected compounds in the interior of planets and their exotic states at high pressure and high temperature(superionic,plastic,partially diffusive state,etc.);new functional materials(superhard,high-energy-density,superconducting,photoelectric materials),*** successful applications demonstrated that MAGUS code can help to accelerate the discovery of interesting materials and phenomena,as well as the significant value of crystal structure predictions in general.

关键词： crystal structure searching materials design ab-initio calculations density functional theory high-pressure phase transition

Photoinduced Light Scattering in Co- and Cr-Doped Lithium Niobate

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Chinese Physics Letters 1999年第2期16卷 137-139页

作者： CHEN Kan ZHANG Ming-sheng CHEN Wan-chun national laboratory of solid state microstructures Department of Physics and Center for Materials AnalysisNanjing UniversityNanjing 210093 Institute of Physics Chinese Academy of SciencesBeijing 100080

Photoinduced light scattering of Co-and Cr-doped lithium niobate crystals is *** light climbing effect is observed in the Co-and Cr-doped lithium niobate *** influences of the incident light wavelength,laser power,sample thickness and doping effects on the light climbing effect are *** photodamage threshold and quicker light climbing are found in the Cr-and Co-doped lithium niobate,which are attributed to the higher space electrical charge field and both different valence and occupation of the doping ions,respectively.

关键词： doping lithium occupation

Anomalous phonon softening in the topological insulator Sn-doped Bi1.1Sb0.9Te2S

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Science China(Physics,Mechanics & Astronomy) 2020年第11期63卷 85-89页

作者： BoWen Li WenChao Jiang GuanYu Chen Ying Xiang Wei Xie YaoMin Dai XiYu Zhu Huan Yang Hai-Hu Wen center for Superconducting Physics and materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093China

Investigations into the phonon behavior provide important information on interactions between different excitations in quantum *** perform a detailed study of the phonon behavior in the topological insulator Sn-doped Bi1.1Sb0.9Te2S using infrared *** observe two IR-active phonon modes at about 64 and 165 cm^1,which are labeled withαandβ,*** the evolution of theβmode with temperature can be well described by the expected anharmonic decay process,theαmode shifts to lower frequencies with decreasing *** an anomalous softening of theαmode may arise from the charged-phonon effect due to the coupling between this mode and the topological surface states in Sn-doped Bi1.1Sb0.9Te2S.

关键词： topological insulator infrared spectroscopy phonon

Ink Dispersion on Qianlong Xuan Paper with Improved Ink Expression

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Journal of materials Science & Technology 2016年第2期32卷 182-188页

作者： Shuyi Wu Xinglong Wu Paul K.Chu Collaborative Innovation center of Advanced microstructures National Laboratory of Solid State Microstructures Nanjing University Department of Physics and materials Science City University of Hong Kong

Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettahility, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.

关键词： Qianlong Xuan paper Wettability Homogeneity Wicking Surface roughness

Phonon and Spin Wave Spectra Study on“in situ Oxidizing Sputtered”Ni/NiO Multilayers

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Chinese Physics Letters 1996年第1期13卷 73-76页

作者： WANG Wen-nai JIANG Zheng-sheng CHENG Guang-xu DU You-wei national laboratory of solid state microstructures Center for Advanced Studies in Science and Technology of MicrostructuresNanjing UniversityNanjing 210093 center of Material analysis Nanjing UniversityNanjing 210093

An improved sputtering method,which is named "in situ oxidizing sputtering",was used to prepare periodic Ni/NiO *** studied in this letter contains 20 pairs of Ni/NiO with period about 100 *** Raman scattering,the low frequency phonon modes are hiterpreted as LA phonon folding effect,which is usually measured in superlattices with a strict periodic *** ferromagnetic resonance spectra were also recorded at room temperature with microwave frequency 9.777 *** analysis of spin wave resonance indicates that Ni sublayers are coupled with each other,which is the mechanism that surely relates to the amorphous-like NiO spacers.

关键词： structure. phonon amorphous

Comparative study of vortex dynamics in CaKFe_4As_4 and Ba_(0.6)K_(0.4)Fe_2As_2 single crystals

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Science Bulletin 2019年第2期64卷 81-90页

作者： Wang Cheng Hai Lin Bing Shen Hai-Hu Wen center for Superconducting Physics and materials National Laboratory of Solid State Microstructures and Department of Physics National Center of Microstructures and Quantum Manipulation Nanjing University School of Physics Sun Yat-sen University

We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe_4As_4(CaK1144) and Ba_(0.6)K_(0.4)Fe_2As_2(BaK122) with similar superconducting transition temperatures. It is found that the magnetization hysteresis loop exhibits a clear second peak effect in BaK122 in wide temperature region while it is absent in CaK1144. However, a second peak effect of critical current density versus temperature is observed in CaK1144, which is however absent in BaK122. The different behaviors of second peak effect in BaK122 and CaK1144 may suggest distinct origins of vortex pinning in different systems. Magnetization and its relaxation have also been measured by using dynamical and conventional relaxation methods for both systems. analysis and comparison of the two distinct systems show that the vortex pinning is stronger and the critical current density is higher in BaK122 system. It is found that the Maley's method can be used and thus the activation energy can be determined in BaK122 by using the time dependent magnetization in wide temperature region, but this is not applicable in CaK1144 *** we present the different regimes with distinct vortex dynamics in the field-temperature diagram for the two systems.

关键词： CaKFe4As4 Ba0.6K0.4Fe2As2 Magnetization hysteresis loop Vortex pinning Second peak effect Vortex dynamics

Robust superconductivity and transport properties in (Li_(1-x)Fe_x)OHFeSe single crystals

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Science China(Physics,Mechanics & Astronomy) 2016年第5期59卷 11-15页

作者： Hai Lin Jie Xing Xi Yu Zhu Huan Yang Hai-Hu Wen center for Superconducting Physics and materials National Laboratory of Solid State Microstructures and Department of PhysicsNational Collaborative Innovation Center of Advanced Microstructures Nanjing University

The recently discovered(Li_(1-x) Fe_x)OHFe Se superconductor with T c about 40 K provides a good platform for investigating the magnetization and electrical transport properties of Fe Se-based superconductors. By using a hydrothermal ion-exchange method,we have successfully grown crystals of(Li_(1-x) Fe_x)OHFe Se. X-ray diffraction on the sample shows the single crystalline Pb O-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around T c=38.3 K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current J s is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic *** dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

关键词： iron chalcogenides critical currents magnetic properties transport properties

Role of Multi-scale Hierarchical Structures in Regulating Wetting state and Wetting Properties of Structured Surfaces

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Journal of Bionic Engineering 2024年第3期21卷 1347-1359页

作者： Yue Jiang Xinyi Li Zhichao Ma Zhihui Zhang Cuie Wen Zhonghao Jiang Nan Lin Luquan Ren Key laboratory of Bionic Engineering of Ministry of Education College of Biological and Agricultural EngineeringJilin UniversityChangchun130022China Hubei Provincial Engineering Technology Research center for Microgrid College of Electrical Engineering and New EnergyChina Three Gorges UniversityYichang443002China School of Mechanical and Aerospace Engineering Jilin UniversityChangchun130025China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVictoria3001Australia Key laboratory of Automobile materials of Ministry of Education College of Materials Science and EngineeringJilin UniversityChangchun130025China state Key laboratory of Inorganic Synthesis and Preparative Chemistry Jilin UniversityChangchun130012China

Amplifying the intrinsic wettability of substrate material by changing the solid/liquid contact area is considered to be the main mechanism for controlling the wettability of rough or structured *** theoretical analysis and experimental exploration,we have found that in addition to this wettability structure amplification effect,the surface structure also simultaneously controls surface wettability by regulating the wetting state via changing the threshold Young angles of the Cassie-Baxter and Wenzel wetting *** wetting state regulation effect provides us with an alternative strategy to overcome the inherent limitation in surface chemistry by tailoring surface *** wetting state regulation effect created by multi-scale hierarchical structures is quite significant and plays is a crucial role in promoting the superhydrophobicity,superhydrophilicity and the transition between these two extreme wetting properties,as well as stabilizing the Cassie-Baxter superhydrophobic state on the fabricated lotus-like hierarchically structured Cu surface and the natural lotus leaf.

关键词： Hierarchical structure Wetting state regulation Wetting transition Superhydrophobicity Superhydrophilicity

Critical couplings in topological-insulator waveguide-resonator systems observed in elastic waves

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national Science Review 2021年第2期8卷 83-94页

作者： Si-Yuan Yu Cheng He Xiao-Chen Sun Hong-Fei Wang Ji-Qian Wang Zi-Dong Zhang Bi-Ye Xie Yuan Tian Ming-Hui Lu Yan-Feng Chen national laboratory of solid state microstructures and Department of materials Science and Engineering Nanjing University Collaborative Innovation center of Advanced microstructures Nanjing University Jiangsu Key laboratory of Artificial Functional materials Nanjing University

Waveguides and resonators are core components in the large-scale integration of electronics, photonics and phononics, both in existing and future scenarios. In certain situations, there is critical coupling of the two components; i.e. no energy passes through the waveguide after the incoming wave couples into the resonator. The transmission spectral characteristics resulting from this phenomenon are highly advantageous for signal filtering, switching, multiplexing and sensing. In the present study, adopting an elastic-wave platform, we introduce topological insulator(TI), a remarkable achievement in condensed matter physics over the past decade, into a classical waveguide-ring-resonator configuration. Along with basic similarities with classical systems, a TI system has important differences and advantages, mostly owing to the spin-momentum locked transmission states at the TI boundaries. As an example, a two-port TI waveguide resonator can fundamentally eliminate upstream reflections while completely retaining useful transmission spectral characteristics, and maximize the energy in the resonator, with possible applications being novel signal processing, gyro/sensing, lasering, energy harvesting and intense wave–matter interactions, using phonons, photons or even electrons. The present work further enhances confidence in using topological protection for practical device performance and functionalities, especially considering the crucial advantage of introducing(pseudo)spins to existing conventional configurations. More in-depth research on advancing phononics/photonics, especially on-chip, is foreseen.

关键词： topological insulators phononic crystals ring resonators waveguide-resonator systems critical couplings