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Soft-mode dynamics in the ferroelectric phase transition of GeTe

npj Computational materials 2021年第1期7卷 1067-1073页

作者： Chen Wang Jiangtao Wu Zezhu Zeng Jan Embs Yanzhong Pei Jie Ma Yue Chen Department of Mechanical Engineering The University of Hong KongHong Kong SARChina Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education) Shenyang National Laboratory for Materials ScienceSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghaiChina Laboratory for Neutron Scattering and Imaging Paul Scherrer InstituteVilligenSwitzerland Interdisciplinary Materials Research Center School of Materials Science and EngineeringTongji UniversityShanghaiChina HKU Zhejiang Institute of Research and Innovation Lin AnChina

GeTe that exhibits a strong anharmonicity and a ferroelectric phase transition between the rhombohedral and cubic structures has emerged as one of the leading thermoelectric ***,combining molecular dynamics simulations and inelastic neutron scattering measurements,the lattice dynamics in GeTe have been investigated to reveal the soft-mode mechanisms across the phase *** have constructed a first-principles-based machine-learning interatomic potential,which successfully captures the dynamical ferroelectric phase transition of GeTe by adopting the neural network *** the low-energy acoustic phonons remain relatively unaffected at elevated temperatures,the high-energy optical,and longitudinal acoustic phonons demonstrate strong renormalizations as evidenced from the vibrational phonon spectra,which are attributed to the large anharmonicity accompanying the phase ***,our results reveal a nonmonotonic temperature dependence of the soft-modes beyond the perturbative *** insight provided by this work into the soft-modes may pave the way for further phonon engineering of GeTe and the related thermoelectrics.

关键词： transition ferroelectric transition

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A Deep Insight of Re-Entrant Martensitic Transformation Mechanism in Co2Cr(Ga,Si) Shape Memory Alloys

SSRN

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SSRN 2024年

作者： Zhao, Yi Zhao, Wenbin Li, Jian Tan, Changlong Zhang, Kun School of Materials Science and Chemical Engineering Harbin University of Science and Technology Harbin150080 China School of Mechanical Power Engineering Harbin University of Science and Technology Harbin150080 China Weihai Polycrystalline Tungsten Molybdenum Technology Co. Ltd Weihai264200 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Liaoning Shenyang110016 China School of Materials Science and Engineering University of Science and Technology of China Liaoning Shenyang110016 China

Co2Cr(Ga,Si) shape memory alloys have a wide application temperature range due to the unique re-entrant martensite phase transformation (RMT) behavior. Nevertheless, the microscopic mechanism of RMT remains elusive and unsystematic. The heart of this investigation lies the comprehensive exploration of phase stability, phase transformation path, and martensite slip direction during RMT from martensite (D022-PM) to austenite (L21-FM). In this work, we systematically investigate the re-entrant martensitic transformation of Co2Cr(Ga,Si) SMAs using first-principles methods for the first time. Firstly, the density of states (DOS) calculation indicates that the stability of L21-FM is higher than D022-PM. The charge density calculation further indicates that the bonding strength between Co atoms and Cr (Si) atoms in the L21-FM phase is the highest. In addition, Fermi surface calculation further reveals that phase instability is due to the Fermi surface nesting caused by electron-phonon coupling. Moreover, the minimum energy path was calculated by the G-SSNEB method for the first time, which indicates the RMT can occur. Finally, the calculation of the elastic constants indicates that RMT is caused by the crystal plane slip of the D022PM phase along the direction. Our calculations provide the electronic-level and thermodynamic mechanism for RMT of Co2Cr(Ga,Si) alloy and shed some light on the revelation of the phase transformation mechanism. © 2024, The Authors. All rights reserved.

关键词： Martensitic transformations

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Automated Global Analysis of Experimental Dynamics through Low-Dimensional Linear Embeddings

arXiv

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arXiv 2024年

作者： Moore, Samuel A. Mann, Brian P. Chen, Boyuan Department of Mechanical Engineering and Materials Science Duke University DurhamNC United States Department of Electrical and Computer Engineering Duke University DurhamNC United States Department of Computer Science Duke University DurhamNC United States

Dynamical systems theory has long provided a foundation for understanding evolving phenomena across scientific domains. Yet, the application of this theory to complex real-world systems remains challenging due to issues in mathematical modeling, nonlinearity, and high dimensionality. In this work, we introduce a data-driven computational framework to derive low-dimensional linear models for nonlinear dynamical systems directly from raw experimental data. This framework enables global stability analysis through interpretable linear models that capture the underlying system structure. Our approach employs time-delay embedding, physics-informed deep autoencoders, and annealing-based regularization to identify novel low-dimensional coordinate representations, unlocking insights across a variety of simulated and previously unstudied experimental dynamical systems. These new coordinate representations enable accurate long-horizon predictions and automatic identification of intricate invariant sets while providing empirical stability guarantees. Our method offers a promising pathway to analyze complex dynamical behaviors across fields such as physics, climate science, and engineering, with broad implications for understanding nonlinear systems in the real world. © 2024, CC BY.

关键词： Nonlinear dynamical systems

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Exciton-driven Floquet-Bloch States in 2D Semiconductors

Exciton-driven Floquet-Bloch States in 2D Semiconductors

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2024 JSAP-Optica Joint Symposia, JSAP 2024

作者： Pareek, Vivek Bacon, David Zhu, Xing Chan, Yang-Hao Bussolotti, Fabio Chan, Nicholas S. Urquizo, Joel Pérez Watanabe, Kenji Taniguchi, Takashi Man, Michael K.L. Madéo, Julien Qiu, Diana Goh, Kuan Eng Johnson da Jornada, Felipe H. Dani, Keshav M. Femtosecond Spectroscopy Unit Okinawa Institute of Science and Technology Graduate University Okinawa Onna904-0495 Japan Institute of Atomic and Molecular Sciences Academia Sinica Physics Division National Center of Theoretical Sciences Taipei Taiwan 2 Fusionopolis Way Singapore138634 Singapore Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Ibaraki Tsukuba305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Ibaraki Tsukuba305-0044 Japan Department of Mechanical Engineering and Materials Science Yale University New HavenCT United States Department of Physics National University of Singapore 2 Science Drive 3 Singapore117551 Singapore Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 50 Nanyang Avenue Singapore639798 Singapore Department of Materials Science and Engineering Stanford University StanfordCA United States Stanford PULSE Institute SLAC National Accelerator Laboratory Menlo ParkCA United States

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A computational framework for modeling distortion during sintering of binder jet printed parts

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Journal of Micromechanics and Molecular Physics 2021年第4期6卷 95-102页

作者： Paudel, Basil J. Conover, Dave Lee, Jung-Kun To, Albert C. Department of Mechanical Engineering and Materials Science University of Pittsburgh PA United States Ansys Inc. Canonsburg PA United States

Sintering of binder jet 3D printed (BJ3DP) parts results in significant nonlinear distortion with typical shrinkage value of 5-20%, which makes design for BJ3DP and post-machining difficult. In this work, a computational modeling framework with calibration and validation procedure is developed to simulate distortion during sintering of BJ3DP parts accurately for the first time. The computational model employs the finite element analysis with a viscoplastic constitutive model that accounts for effects of gravity and friction. A calibration procedure is proposed to obtain values of different model parameters systematically through dilatometric, gravity bending, and grain growth experiments. For model validation, four bridges with different spans and a second part with a circular hole and two free overhangs are designed. The calibration procedure is applied to develop a computational model for sintered 316L stainless steel BJ3DP parts. The displacements at various locations on the sintered parts are simulated using the calibrated model and are found to have errors less than 3.5% compared to those obtained by experiment. © 2021 World Scientific Publishing Company.

关键词： additive manufacturing binder jet distortion modeling simulation Sintering

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Techno-Economic Assessment of Offshore Wind and Hybrid Wind-Wave Farms with Energy Storage Systems

SSRN

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SSRN 2023年

作者： Gao, Qiang Bechlenberg, Alva Vakis, Antonis I. Ertugrul, Nesimi Jayawardhana, Bayu Ding, Boyin The University of Adelaide School of Electrical and Electronic Engineering Adelaide Australia University of Groningen Computational Mechanical and Materials Engineering Groningen Netherlands University of Groningen Discrete Technology and Production Automation Groningen Netherlands The University of Adelaide School of Mechanical Engineering Adelaide Australia Faculty of Science and Engineering

Ocean renewables (such as offshore wind and wave) are abundant and essential energy resources for supporting future emission-free targets. However, their energy intermittency and high cost have hindered commercialization and wide-scale implementations of these ocean energy technologies. This paper focuses on both issues and aims to increase the dispatchability of ocean energy farm, by investigating the potential of a hybrid wind and wave energy platform with various energy storage systems (ESSs). In the paper, a novel method is proposed to assess the ESS for an offshore renewable energy farm to guarantee the energy dispatchability to the local demand. The effect of two farm configurations on the ESS capacity is analysed: one involves wind turbines only and the other one uses a hybrid configuration (with wind and wave generation subsystems). Lifecycle cost models of energy farms are developed and the economic feasibility of different energy storage systems are investigated. The sensitivity of energy farm configurations and the energy storage systems to the resource characteristics at multiple locations are also studied. The results indicate that the combined wind and wave energy farm significantly reduces the energy storage system capacity requirement and provides competitive lifecycle costs compared to the stand-alone wind energy farm, though the amount of these benefits vary on the local resource characteristics. In addition, it was concluded that the Lithium-ion battery option in a combined energy farm offers better overall performance over the other storage options considered. © 2023, The Authors. All rights reserved.

关键词： Energy storage

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In situ structural determination of 3d and 5d perovskite oxides under high pressure by synchrotron x-ray diffraction

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Physical Review B 2023年第13期108卷 134106-134106页

作者： Jie Chen Jiaming He Yanyao Zhang Stella Chariton Vitali Prakapenka Kazunari Yamaura Jung-Fu Lin J. B. Goodenough J.-S. Zhou Materials Science and Engineering Program Mechanical Engineering University of Texas at Austin Austin Texas 78712 USA Department of Earth and Planetary Sciences Jackson School of Geosciences The University of Texas at Austin Austin Texas 78712 USA Center for Advanced Radiation Sources The University of Chicago Illinois 60637 USA Research Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan Graduate School of Chemical Sciences and Engineering Hokkaido University North 10 West 8 Kita-ku Sapporo Hokkaido 060–0810 Japan

In contrast to the Mott transition found in RNiO3 (R= rare earths), the metal-insulator transition temperature in the perovskite NaOsO3 is not sensitive to pressure. The peculiarity may be correlated to how the crystal structure of NaOsO3 responds to high pressure, which has been rarely studied so far. The pressure-induced bond-length shrinking can increase the orbital overlap integral and therefore the electron bandwidth. However, in the orthorhombic perovskite structure, the pressure-induced bending in the bond angle Os-O-Os may compensate for the bandwidth broadening due to the bond-length shrinking in some circumstances. A recent structural study on polycrystalline NaOsO3 indicated that orthorhombic distortion is enlarged under high pressure. But, how the local structure changes under pressure remains unknown. Moreover, a highly unusual phase transition from the orthorhombic phase (Pbnm) to a polar phase (Pbn21) occurs at around 18 GPa [Sereika et al., npj Quantum Mater. 5, 66 (2020)]. Motivated by these concerns, we have done a more comprehensive structural study on NaOsO3 using single-crystal diffraction with synchrotron radiation at high pressures up to 41 GPa. Diffraction patterns over the entire pressure range can be refined well with the Pbnm structural model. Moreover, the refinement results reveal in detail how the local structures change under pressure corresponding to the enhanced orthorhombic distortion from the lattice parameters. We have carried out a systematic study for understanding the pressure effect on the orthorhombic perovskites in the context of the influences of the charge distributions in the ABO3 formula, i.e., A3+B3+O3, A2+B4+O3, and A1+B5+O3 and the B-site cations from the 3d to the 4d and 5d row of elements. To fulfill this purpose, we have revisited two families of 3d perovskites: RCrO3 and RFeO3.

关键词： Phase transitions Crystal structures X-ray diffraction

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Application of level-set type topology optimization for defect topology identification analysis using hammering response data

引用

materials Today: Proceedings 2023年

作者： Kurahashi, Takahiko Koike, Towa Kishida, Masayuki Murakami, Yuki Ikeda, Fujio Department of Mechanical Engineering Institute of GIGAKU Nagaoka University of Technology Niigata Nagaoka Japan Mechanical Engineering Master's Program Graduate School of Engineering Nagaoka University of Technology Niigata Nagaoka Japan Science of Technology Innovation 5-year Integrated Doctoral Program Graduate School of Engineering Nagaoka University of Technology Niigata Nagaoka Japan Department of Civil Engineering National Institute of Technology Nagaoka College Niigata Nagaoka Japan Department of Mechanical Engineering National Institute of Technology Nagaoka College Niigata Nagaoka Japan

In this study, we presented the defect identification analysis based on the level-set type topology optimization using hammering testing data. To simulate the oscillation behavior of concrete structure, the equation of motion in three dimensions is introduced as the governing equation. The performance function is defied by the time integral of the squared residual between the computed and observed displacements. The problem is to find the defect topologies so as to minimize the performance function. In the model with a small number of observation points, it was found that nonexistent defects disappeared by using the weighted sensitivity method. In addition, it was confirmed that the model with a large number of observation points did not show the same tendency as the model with a small number of observation points because the accuracy of defect identification increased as the number of observation points increased. © 2023

关键词： Defects

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Microwave-assisted biosynthesis of silver nanoparticles for potential antibacterial activity

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Applied Nanoscience (Switzerland) 2024年第12期14卷 1115-1124页

作者： Kala, Anuskha Uniyal, Santoshi Saini, Krati Dhyani, Reena Joshi, Deepika Verma, Rashmi Kar, Kamal K. Chamoli, Pankaj School of Basic and Applied Sciences Department of Biotechnology Shri Guru Ram Rai University Uttarakhand Dehradun248001 India School of Basic and Applied Sciences Department of Physics Shri Guru Ram Rai University Uttarakhand Dehradun248001 India Department of Physics Women Institue of Technology Uttarakhand Dehradun248007 India Siddhartha Institute of Pharmacy Uttarakhand Dehradun248013 India Advanced Nanoengineering Materials Laboratory Department of Mechanical Engineering and Materials Science Programme Indian Institute of Technology Kanpur Kanpur208016 India

The present study demonstrates the creation of silver nanoparticles (Ag NPs) in an environmentally benign manner from Cymbopogon citratus leaves extracts by employing microwave-assisted synthesis at a low power of 400 W for a short period of 180 s. The produced Ag NPs are thoroughly characterized using methods like X-ray diffraction (XRD), UV–visible spectroscopy, scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS). These Ag NPs form clusters and have unique plate-like shapes with average particle size of ~ 165 nm. To evaluate their antibacterial activity, the produced Ag NPs are tested against both gram-positive bacteria (S. aureus) and gram-negative bacteria (E. Coli, S. typhi, and Pseudomonas) at varied concentrations (1–5 mg/L). The results show strong antibacterial activity, against both gram-positive bacteria (S. aureus) and gram-negative bacteria (E. Coli, S. typhi, and Pseudomonas);and show the largest zone of inhibition diameters at 23 mm (~ 3 mg/L) and 26 mm (~ 5 mg/L) for S. aureus and Pseudomonas, respectively. The ecological potential of Cymbopogon citratus extracts as sources for the environmentally friendly synthesis of Ag NPs is highlighted in this work and the produced Ag NPs are a viable option for antibacterial treatments against pathogenic microbes. © King Abdulaziz City for science and Technology 2024.

关键词： Silver nanoparticles

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One-Pot Synthesis of Tetraarylpyrrolo[3,2-b]pyrrole Dopant-Free Hole-Transport materials for Inverted Perovskite Solar Cells

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Chinese Journal of Chemical Physics 2021年第2期34卷 217-226,I0002页

作者： Liang-sheng Duan Quan-ping Wu Yuan-yuan Xu Hui Wang Zhe Sun Yu Chen Song Xue School of Materials Science and Engineering Tianjin Key Laboratory of the Design and Intelligent Control of the Advanced Mechanical SystemSchool of Mechanical EngineeringTianjin University of TechnologyTianjin 300384China

Four organic smallmolecule hole transport materials(D41, D42,D43 and D44) of tetraarylpyrrolo[3,2-b]pyrroles were prepared. They can be used without doping in the manufacture of the inverted planar perovskite solar cells. Tetraarylpyrrolo[3,2-b]pyrroles are accessible for one-pot synthesis.D42, D43 and D44 possess acceptor-π-donor-π-acceptor structure, on which the aryl bearing substitutes of cyan, fluorine and trifluoromethyl, respectively. Instead, the aryl moiety of D41 is in presence of methyl with a donor-π-donor-π-donor structure. The different substitutes significantly affected their molecular surface charge distribution and thin-film morphology, attributing to the electron-rich properties of fused pyrrole ring. The size of perovskite crystalline growth particles is affected by different molecular structures,and the electron-withdrawing cyan group of D42 is most conducive to the formation of large perovskite grains. The D42 fabricated devices with power conversion efficiency of17.3% and retained 55% of the initial photoelectric conversion efficiency after 22 days in dark condition. The pyrrolo[3,2-b]pyrrole is efficient electron-donating moiety for hole transporting materials to form good substrate in producing perovskite thin film.

关键词： Pyrrole[3,2-b]pyrrole Hole-transporting materials Organic small molecules Dopant-free Perovskite solar cells

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