Long-Qing Chen
· Donald W. Hamer Professor of Materials Science and EngineeringVerifiedPennsylvania State University · Department of Materials Science and Engineering
Active 1982–2026
About
Long-Qing Chen is the Donald W. Hamer Professor of Materials Science and Engineering, as well as a Professor of Engineering Science and Mechanics and Mathematics at Pennsylvania State University. He received his B.S. in Materials Science and Engineering from Zhejiang University in China in 1982, followed by an M.S. from the State University of New York at Stony Brook in 1985, and a Ph.D. from MIT in 1990. His research focuses on the development and application of mesoscale phase-field models to understand and design structural, functional, multiferroic heterostructures, polymer composites, and energy materials. He specializes in analytical thermodynamic and kinetic theories of phase transitions, interfaces, and microstructures, and in multiscale models that integrate atomistic calculations with phase-field methods to predict microstructure evolution during various materials processes. Dr. Chen has made significant contributions to the understanding of microstructure evolution during phase transformations, grain growth, ferroelectric and multiferroic domain switching, and coupled electronic and structural transitions in functional and quantum materials. He is the director of the DOE CMS Center for Computational Mesoscale Materials Science and the founding Editor-in-Chief of npj Computational Materials. With over 1,000 publications and more than 107,000 citations, his work has had a profound impact on the field of computational materials science. He has also authored a textbook on thermodynamics of materials, which has been widely accessed and translated into Chinese.
Research topics
- Materials science
- Physics
- Optoelectronics
- Condensed matter physics
- Composite material
- Computer Science
- Quantum mechanics
- Optics
- Chemistry
- Thermodynamics
- Pathology
- Mathematics
- Virology
- Medicine
- Statistical physics
- Operating system
- Organic chemistry
- Nanotechnology
- Metallurgy
- Computational science
- Chemical physics
Selected publications
Decoding THz‐Driven Dynamic Fingerprints of Ferroelectric Nanotwin Networks
Advanced Materials · 2026-05-02
articleOpen accessABSTRACT Ultrafast polarization dynamics in ferroelectrics are of considerable interest for high‐speed tunable dielectrics and electro‐optics. Extended domain wall networks formed in ferroelectric twin nanodomains can support collective dynamics in the terahertz regime but require techniques that track polarization and strain evolution driven by ultrafast stimulus. Here, we use multi‐modal probing of THz‐pulse‐driven excitations in PbTiO 3 /SrTiO 3 superlattices by combining X‐ray free electron laser measurements that directly tracks lattice changes, with optical second harmonic generation that tracks the electronic potential coupled with the lattice potential. Dynamical phase‐field modeling enables fingerprinting of these collective modes as superpositions of domain “breathing” through wall oscillations and polarization “rotations” with still walls. Ultrafast domain wall motion at 0.1–0.5 THz is observed at practical fields of 100 kV/cm with wall velocities of >4000 m/s, approaching typical speed of sound in PbTiO 3 . A unique “charging” mode is discovered that can electrically charge and discharge domain walls on ∼4 ps time scale thus dynamically tuning wall conductivity. Integrated experimental and theoretical fingerprinting of the dynamical landscape presented here enables ultrafast control of ferroics for high‐speed microelectronics and optical applications.
Proximity Ferroelectricity in Compositionally Graded Structures
Advanced Electronic Materials · 2026-02-19
articleOpen accessABSTRACT Proximity ferroelectricity is a novel paradigm for inducing ferroelectricity in a non‐ferroelectric polar material, such as AlN or ZnO that are typically unswitchable with an external field below their dielectric breakdown field. When placed in direct contact with a thin switchable ferroelectric layer (such as Al 1‐x Sc x N or Zn 1‐x Mg x O), they become a practically switchable ferroelectric. Using the thermodynamic Landau‐Ginzburg‐Devonshire theory, in this work, we perform the finite element modeling of the polarization switching in the compositionally graded AlN‐Al 1‐x Sc x N, ZnO‐Zn 1‐x Mg x O, and MgO‐Zn 1‐x Mg x O structures sandwiched in both a parallel‐plate capacitor geometry as well as in a sharp probe‐planar electrode geometry. We reveal that the compositionally graded structure allows the simultaneous switching of spontaneous polarization in the whole system by a coercive field significantly lower than the electric breakdown field of unswitchable polar materials. The physical mechanism is the depolarization electric field determined by the gradient of chemical composition “x”. The field lowers the steepness of the switching barrier in the otherwise unswitchable parts of the compositionally graded AlN‐Al 1‐x Sc x N and ZnO‐Zn 1‐x Mg x O structures. In the MgO‐like regions of the compositionally graded MgO‐Zn 1‐x Mg x O structure, a shallow double‐well free energy potential emerges. Proximity ferroelectric switching of the compositionally graded structures placed in the probe‐electrode geometry occurs due to nanodomain formation under the tip. We predict that a gradient of chemical composition “x” significantly lowers effective coercive fields of the compositionally graded AlN‐Al 1‐x Sc x N and ZnO‐Zn 1‐x Mg x O structures compared to the coercive fields of the corresponding multilayers with a uniform chemical composition in each layer. A tip‐induced switching further lowers the coercive field, enabling control of ferroelectric domains in otherwise unswitchable compositionally graded structures, which can provide nanoscale domain control for memory, actuation, sensing, and optical applications.
Open MIND · 2026-02-12
preprintSenior authorInspired by recent discovery of metallic $d$-wave altermagnetism in KV$_2$Se$_2$O, we develop a self-consistent microscopic many-body calculation of density-wave order for an itinerant altermagnetic metal. We show that the strong $d$-wave spin-momentum locking inherent to the altermagnetic band structure reconstructs the Fermi surface into spin-selective quasi-1D open sheets. This unique topology of Fermi surface drives an instability toward spin-resolved electronic charge density waves (CDWs), in which the ordering wave vectors for spin-up and spin-down electrons condense along two mutually orthogonal directions, forming spin-resolved stripe phases. As a consequence, this results in pronounced gap openings near the Fermi surface, and the superposition of these spin-resolved stripe orders leads to a checkerboard CDW in the charge channel and an antiphase spin-density-wave modulation in the spin channel. Upon increasing temperature, the density-wave order melts at $T_c$ due to thermal phase fluctuation while the gap opening persists, giving rise to a robust pseudogap regime, which eventually closes at a higher temperature $T_g$. The resulting simulations quantitatively reproduce the key features observed in the spectroscopic measurements, offering a consistent and generic understanding of the reported phenomena in KV$_2$Se$_2$O and, more broadly, in metallic altermagnets with strong spin-momentum locking.
Microorganisms · 2026-04-01
articleOpen accessTo investigate the main drivers of rhizosphere soil microbial community structure and diversity in Camellia reticulata, this study collected rhizosphere soil samples from six regions at two soil depths (0–30 cm and 30–60 cm). Using high-throughput sequencing, we systematically analyzed the effects of soil environmental factors on microbial communities. The results showed that the dominant bacterial phyla were Proteobacteria, Acidobacteriota, Chloroflexi, Actinobacteriota, and Bacteroidota, while the dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. Alpha diversity of both bacterial and fungal communities was higher in surface soils (0–30 cm) than in deeper layers (30–60 cm), although the differences were not statistically significant (p > 0.05). Soil pH, potassium content (K), and catalase activity (S-CAT) were identified as the main environmental factors significantly correlated with microbial community structure. Network analysis identified Acidobacteriota and Ascomycota as highly connected taxa within microbial networks, suggesting their potential importance in maintaining network structure. This study reveals the vertical differentiation characteristics of rhizosphere microbial communities in C. reticulata and their responses to environmental factors, providing a theoretical basis for cultivation management and rhizosphere microecological regulation.
ArXiv.org · 2026-02-12
articleOpen accessSenior authorInspired by recent discovery of metallic $d$-wave altermagnetism in KV$_2$Se$_2$O, we develop a self-consistent microscopic many-body calculation of density-wave order for an itinerant altermagnetic metal. We show that the strong $d$-wave spin-momentum locking inherent to the altermagnetic band structure reconstructs the Fermi surface into spin-selective quasi-1D open sheets. This unique topology of Fermi surface drives an instability toward spin-resolved electronic charge density waves (CDWs), in which the ordering wave vectors for spin-up and spin-down electrons condense along two mutually orthogonal directions, forming spin-resolved stripe phases. As a consequence, this results in pronounced gap openings near the Fermi surface, and the superposition of these spin-resolved stripe orders leads to a checkerboard CDW in the charge channel and an antiphase spin-density-wave modulation in the spin channel. Upon increasing temperature, the density-wave order melts at $T_c$ due to thermal phase fluctuation while the gap opening persists, giving rise to a robust pseudogap regime, which eventually closes at a higher temperature $T_g$. The resulting simulations quantitatively reproduce the key features observed in the spectroscopic measurements, offering a consistent and generic understanding of the reported phenomena in KV$_2$Se$_2$O and, more broadly, in metallic altermagnets with strong spin-momentum locking.
A structure-preserving scheme for the time-dependent Ginzburg–Landau model with BCS gap coupling
Journal of Computational Physics · 2026-04-23
articlephysica status solidi (a) · 2025-12-10
articleOpen accessTo investigate the effects of varying grinding angles on surface andsubsurface microdamage in silicon wafers, a combined method integrating nanogrinding experiments and numerical simulations is proposed. A systematic analysis of surface roughness, surface morphology, and subsurface damage mechanisms during the silicon wafer grinding process is conducted based on molecular dynamics. Focusing on the characteristics of grinding angle‐induced surface damage in silicon wafers, mathematical models are established to correlate grinding angles with tangential forces, dislocation evolution, and crystalline structure changes. Key parameters, including tangential force, dislocation density, and crystalline phase transformations under various grinding angles, are systematically collected and analyzed. Comprehensive analysis indicates that at a 30° grinding angle, the damage layer thickness is merely 8.0 nm, representing a 27.9% reduction compared to the 45° angle. Concurrently, the surface roughness remains at 0.012965, demonstrating a 15.1% improvement over the 45° angle. Although the roughness at 15° is marginally lower, its material removal accumulation height is significantly less than the 43.8 Å recorded at 30°. Consequently, the 30° grinding angle represents the optimal compromise between low damage and high efficiency during silicon wafer grinding. This provides crucial theoretical justification and quantitative support for process optimization.
Terahertz-field activation of polar skyrons
Nature Communications · 2025-10-09 · 3 citations
articleOpen accessUnraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuity at the nanometer scale with nontrivial topology, leading to previously unexplored collective modes. Here, using terahertz-field excitation and femtosecond x-ray diffraction, we discover subterahertz collective modes, dubbed "skyrons", which appear as swirling patterns of atomic displacements functioning as atomic-scale gearsets. The key to activating skyrons is the use of the THz field that couples primarily to skyrmion domain walls. Momentum-resolved time-domain measurements of diffuse scattering reveal an avoided crossing in the dispersion relation of skyrons. Atomistic simulations and dynamical phase-field modeling provide microscopic insights into the three-dimensional crystallographic and polarization dynamics. The amplitude and dispersion of skyrons are demonstrated to be controlled by sample temperature and electric-field bias. The discovery of skyrons and their coupling with terahertz fields opens avenues for ultrafast control of topological polar structures.
Industrial Crops and Products · 2025-10-10 · 1 citations
articleOpen accessIn order to effectively utilize the oleoresin resources of introduced pine species, the monthly variation patterns of the chemical composition of oleoresin from Pinus elliottii Engelm. (S), Pinus taeda L. (H), Pinus caribaea var. bahamensis (Griseb.) W. H. Barrett & Golfari (PCB), Pinus caribaea var. caribaea Morelet (PCC) and Pinus caribaea var. hondurensis (Sénécl.) W. H. Barrett & Golfari (PCH) were analyzed by gas chromatography-mass spectrometry and gas chromatography. The results showed that the oleoresin from the five introduced pine species was similar in compound types and mainly composed of monoterpenes and diterpenes. The types of compounds remained stable across different months. Oleoresin from five introduced pine species could be easily and quickly distinguished based on the differences in the relative contents of the main compounds ( α -pinene, β -pinene, β -phellandrene and isopimaric acid). The relative contents of the main compounds in the oleoresin fluctuated in different months. In months with a significant temperature decrease, both the number of oleoresin-secreting individual plants decreased and the fluctuation range of the main compounds’ relative contents increased. In December, the number of oleoresin-secreting individual of PCB decreased from 30 to 23. In January of the following year, the number of oleoresin-secreting individual of S, H, PCC and PCH decreased from 30 to 16, 21, 19 and 21 respectively. The relative contents of α -pinene, β -pinene, and β -phellandrene in the oleoresin of PCB, PCC, and PCH reached their minimum values in February; conversely, those in the oleoresin of S and H reached their maximum values the in February. This work has important guiding significance for the identification of oleoresin sources, the selection of oleoresin raw materials, the breeding of superior individual plants, and the determination of the optimal resin-tapping time in actual forestry production. • The chemical composition of oleoresin in 5 pine species had been reported monthly. • Proposed a method for analyzing the source of oleoresin through chemical composition. • First discovery of sesquiterpenes in oleoresin of Pinus caribaea Morelet. • The response of oleoresin secretion in pines under temperature changes was studied. • Proposed a selecting method for high-quality oleoresin tree species and individuals.
Materials · 2025-12-04
articleOpen accessRestrictive regulations on the use of peat and increasing consumption in modern horticulture production have created an irreconcilable contradiction. Wood fibers (WF) produced from forestry residues are considered as a promising peat substitution. However, their poor water- and nutrient-holding capacity limit their application. Here, wood fiber–hydrogel composite (WF-Gel) was developed via a one-pot strategy by grafting poly(acrylic acid-co-acrylamide) (P(AA-co-AM)) onto WF. The structure of the hydrogel network incorporated with WF was confirmed by FTIR spectrophotometry, scanning electron microscopy, X-ray diffractometry, and thermogravimetric analysis. The growing substrate amended with WF-Gel showed higher physical properties, including water-filled porosity (~62.33%) and water-holding capacity (~44.93%) compared with peat incorporated with WF. The pot experiment revealed that WF-Gel significantly increases the chlorophyll content and relative growth rate of choy sum (Brassica rapa var. parachinensis), especially at the initial transplanting stage. Moreover, choy sum grown in a substrate containing WF-Gel showed a significant increase in biomass accumulation. Additionally, nutrient content and irrigation water-use efficiency data indicated that WF-Gel as a growing medium strongly promotes the water and nutrient efficiency of choy sum. Therefore, the incorporation of this hydrogel modification strategy is a promising approach to promote the water- and nutrient-use efficiency of WF as a soilless substrate component.
Recent grants
Phase-field Modeling of Flexoelectric Contributions to Ferroelectricity
NSF · $315k · 2014–2018
NIRT: Strain-Enhanced Nanoscale Ferroelectrics
NSF · $1.4M · 2005–2011
Microstructure Evolution in Solids with External Constraints and Defects
NSF · $270k · 2001–2006
NSF · $400k · 2010–2015
GOALI: Understanding and Predicting Li Dendrite Formation in Li-ion Batteries
NSF · $521k · 2012–2017
Frequent coauthors
- 192 shared
Yulan Li
- 192 shared
Ce‐Wen Nan
State Key Laboratory of New Ceramics and Fine Processing
- 168 shared
Darrell G. Schlom
Leibniz Institute for Crystal Growth
- 128 shared
Zi‐Kui Liu
Pennsylvania State University
- 124 shared
Jia‐Mian Hu
- 121 shared
R. Ramesh
- 115 shared
Xiaoqing Pan
University of California, Irvine
- 113 shared
Venkatraman Gopalan
Education
- 1992
Postdoc with Armen G. Khachaturyan, Materials Science and Engineering
Rutgers University
- 1990
Ph.D., Materials Science and Engineering
Massachusetts Institute of Technology
- 1985
M.S., Materials Science and Engineering
Stony Brook University
- 1982
B.S., Materials Science and Engineering
Zhejiang University
Awards & honors
- Fellow of the Canadian Academy of Engineering
- Member of European Academy of Sciences and Arts
- NSF Career Awards
- American Ceramic Society Coble Award
- IEEE Ferroelectric Young Investigator Award
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