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Phase-field method and Materials Genome Initiative(MGI)

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Chinese Science Bulletin 2014年第15期59卷 1641-1645页

作者： long-qing chen Department of Materials Science and Engineering Penn State University University Park PA 16802 USA

Predicting and controlling the microstructure evolution within a material are considered as the‘‘holy grail’’of materials science and *** important engineering materials are designed by controlling their phase transformations and microstructure *** include the improvement of mechanical properties through solid-state precipitation reactions in Nibased superalloys and age-hardened Al alloys,the useful dielectric properties and electro-mechanical coupling effects by manipulating the phase transitions in ferroelectric crystals,and the memory effect of shape-memory alloys by utilizing martensitic ***-field method has become the method of choice for modeling three-dimensional microstructure evolution for a wide variety of materials *** short article briefly discusses the potential roles that phase-field method can play in the Materials Genome Initiative.

关键词：材料科学与工程基因组计划相场方法马氏体相变超耐热合金组织演变形状记忆合金工程材料

Perspective: voltage control of magnetization in multiferroic heterostructures

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National Science Review 2019年第4期6卷 621-624页

作者： Jia-Mian Hu Ce-Wen Nan long-qing chen Department of Materials Science and Engineering University of Wisconsin–Madison State Key Lab of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Department of Materials Science and Engineering Pennsylvania State University

Multiferroic materials host ferromagnetic and ferroelectric orders either in the same phase, or separately in distinct magnetic and ferroelectric phases. In some multiferroic materials, the two distinct ferroic orders can be strongly coupled (namely, magnetoelectric coupling)[1], which can be exploited for achieving new functionalities. For example, it allows for controlling magnetization with a voltage rather than a magnetic-field-generating electric current, providing an energy-efficient

关键词： Perspective voltage control of magnetization in multiferroic heterostructures AFM

Strain-mediated voltage-controlled switching of magnetic skyrmions in nanostructures

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npj Computational Materials 2018年第1期4卷 147-153页

作者： Jia-Mian Hu Tiannan Yang long-qing chen Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Materials Science and Engineering University of Wisconsin–MadisonMadisonWI 53706USA

Magnetic skyrmions are swirling spin structures stabilized typically by the Dyzaloshinskii-Moriya *** existing control of magnetic skyrmions has often relied on the use of an electric current,which may cause overheating in densely packed *** we demonstrate,using phase-field simulations,that an isolated Néel skyrmion in a magnetic nanodisk can be repeatedly created and deleted by voltage-induced strains from a juxtaposed *** a skyrmion switching is non-volatile,and consumes only~0.5 fJ per switching which is about five orders of magnitude smaller than that by current-induced *** is found that the strain-mediated skyrmion creation occurs through an intermediate vortex-like spin structure,and that the skyrmion deletion occurs though a homogenous shrinkage during which the Néel wall is temporarily transformed to a *** findings are expected to stimulate experimental research into strain-mediated voltage control of skyrmions,as well as other chiral spin structures for low-power spintronics.

关键词： vortex magnetic repeatedly

Simultaneous Prediction of Morphologies of a Critical Nucleus and an Equilibrium Precipitate in Solids

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Communications in Computational Physics 2010年第4期7卷 674-682页

作者： Lei Zhang long-qing chen Qiang Du Department of Mathematics Penn State UniversityPA 16802USA Department of Materials Science and Engineering Penn State UniversityPA 16802USA

We investigate the critical nucleus and equilibrium morphologies duringprecipitation of a second-phase particle in a solid. We show that a combination ofdiffuse-interface description and a constrained string method is able to predict boththe critical nucleus and equilibrium precipitate morphologies simultaneously without a priori assumptions. Using the cubic to cubic transformation as an example, it isdemonstrated that the maximum composition within a critical nucleus can be eitherhigher or lower than that of equilibrium precipitate while the morphology of an equilibrium precipitate may exhibit lower symmetry than the critical nucleus resulted fromelastic interactions.

关键词： Phase field diffuse interface nucleation critical nucleus constrained string method elasticity

A high-Nb-TiAl alloy with ultrafine-grained structure fabricated by cryomilling and spark plasma sintering

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Rare Metals 2023年第5期42卷 1678-1685页

作者： Hao Deng Yong-Qiang Wei Jun Tang Ai-Jun chen long-qing chen Zu-Xi Xia Key Laboratory of Radiation Physics and Technology of Ministry of Education Institute of Nuclear Science and TechnologySichuan UniversityChengdu610064China The Second Research Institute of Civil Aviation Administration of China(CAAC) Chengdu610064China

In this work,an ultrafine-grained high-Nb-TiAl alloy with a nominal composition of Ti-45Al-8Nb-0.2W-0.2B(at%)was prepared by cryomilling and subsequent spark plasma sintering(SPS)*** chemical composition,particle size,morphology and crystallite size of cryomilled powder were *** is found that cryomilling can effectively reduce the particle size and enhance grain *** ingots sintered at 900 and 1000℃ show an equiaxed near-γmicrostructure with grain sizes<700 nm,while the sample sintered at 1100℃exhibits duplex ***,the one sintered at 1000℃ has excellent mechanical properties,whose compression yield strength,fracture strength,bending strength and plastic strain achieve 1310,2174,578 MPa and 16.8%,*** reasons for the effect of cryomilling and the mechanical behavior of sintered ingots were *** is suggested that cryomilling in combination with SPS is an effective way to synthesize high-NbTiAl alloy with ultrafine-grained structure.

关键词： Cryomilling Spark plasma sintering Titanium aluminide Ultrafine-grained structure

Understanding and designing magnetoelectric heterostructures guided by computation:progresses,remaining questions,and perspectives

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npj Computational Materials 2017年第1期3卷 304-324页

作者： Jia-Mian Hu Chun-Gang Duan Ce-Wen Nan long-qing chen Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA Key Laboratory of Polar Materials and Devices Ministry of EducationEast China Normal UniversityShanghaiChina School of Materials Science and Engineering and State Key Lab of New Ceramics and Fine ProcessingTsinghua UniversityBeijing 100084China

Magnetoelectric composites and heterostructures integrate magnetic and dielectric materials to produce new functionalities,e.g.,magnetoelectric responses that are absent in each of the constituent materials but emerge through the coupling between magnetic order in the magnetic material and electric order in the dielectric *** magnetoelectric coupling in these composites and heterostructures is typically achieved through the exchange of magnetic,electric,or/and elastic energy across the interfaces between the different constituent materials,and the coupling effect is measured by the degree of conversion between magnetic and electric energy in the absence of an electric *** strength of magnetoelectric coupling can be tailored by choosing suited materials for each constituent and by geometrical and microstructural *** this article,we discuss recent progresses on the understanding of magnetoelectric coupling mechanisms and the design of magnetoelectric heterostructures guided by theory and *** outline a number of unsolved issues concerning magnetoelectric *** compile a relatively comprehensive experimental dataset on the magnetoelecric coupling coefficients in both bulk and thin-film magnetoelectric composites and offer a perspective on the data-driven computational design of magnetoelectric composites at the mesoscale microstructure level.

关键词： composites material coupling

A Spectral Iterative Method for the Computation of Effective Properties of Elastically Inhomogeneous Polycrystals

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Communications in Computational Physics 2012年第3期11卷 726-738页

作者： Saswata Bhattacharyya Tae Wook Heo Kunok Chang long-qing chen Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA

We report an efficient phase field formalism to compute the stress distribution in polycrystalline materials with arbitrary elastic inhomogeneity and *** dependence of elastic stiffness tensor on grain orientation is taken into account,and the elastic equilibrium equation is solved using a spectral iterative perturbation *** discuss its applications to computing residual stress distribution in systems containing arbitrarily shaped cavities and cracks(with zero elastic modulus)and to determining the effective elastic properties of polycrystals and multilayered composites.

关键词： Elasticity spectral method iterative method

First-principles calculations of lattice dynamics and thermal properties of polar solids

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npj Computational Materials 2016年第1期2卷 163-172页

作者： Yi Wang Shun-Li Shang Huazhi Fang Zi-Kui Liu long-qing chen Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPennsylvaniaPAUSA

Although the theory of lattice dynamics was established six decades ago,its accurate implementation for polar solids using the direct(or supercell,small displacement,frozen phonon)approach within the framework of density-function-theory-based first-principles calculations had been a challenge until *** arises from the fact that the vibration-induced polarization breaks the lattice periodicity,whereas periodic boundary conditions are required by typical first-principles calculations,leading to an artificial macroscopic electric *** article reviews a mixed-space approach to treating the interactions between lattice vibration and polarization,its applications to accurately predicting the phonon and associated thermal properties,and its implementations in a number of existing phonon codes.

关键词： field lattice solids

Analytical and numerical modeling of optical second harmonic generation in anisotropic crystals using #SHAARP package

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npj Computational Materials 2022年第1期8卷 2343-2354页

作者： Rui Zu Bo Wang Jingyang He Jian-Jun Wang Lincoln Weber long-qing chen Venkatraman Gopalan Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA Materials Science Division Lawrence Livermore National LaboratoryLivermoreUSA Department of Engineering Science and Mechanics The Pennsylvania State UniversityUniversity ParkPA16802USA Department of Mathematics The Pennsylvania State UniversityUniversity ParkPA16802USA Department of Physics Pennsylvania State UniversityUniversity ParkPA16802USA

Electric-dipole optical second harmonic generation(SHG)is a second-order nonlinear process that is widely used as a sensitive probe to detect broken inversion symmetry and local polar *** modeling of the SHG polarimetry of a nonlinear optical material is essential to extract its point group symmetry and the absolute nonlinear *** literature on SHG analysis involves numerous approximations and a wide range of(in)*** have developed an open-source package called the Second Harmonic Analysis of Anisotropic Rotational Polarimetry(♯***)which derives analytical and numerical solutions of reflection SHG polarimetry from a single interface(.si)for bulk homogeneous crystals with arbitrary symmetry group,arbitrary crystal orientation,complex and anisotropic linear dielectric tensor with frequency dispersion,a general SHG tensor and arbitrary light polarization.♯*** enables accurate modeling of polarimetry measurements in reflection geometry from highly absorbing crystals or wedge-shaped transparent *** package is extendable to multiple interfaces.

关键词： arbitrary symmetry harmonic