Materials Science · Cross-listed from physics.chem-ph
Correlation-Driven Singlet–Triplet Inversion and Optical Spectra of N-Substituted Phenalenyls: Insights from PPP-FCI and TDDFT
Medha Rakshit and Alok Shukla
Several researchers have reported an atypical inversion of the lowest singlet ($S_{1}$) and triplet ($T_{1}$) excited states in nitrogen-substituted planar hydrocarbons. Contrary to Hund's rule of maximum multiplicity, poly-aza derivatives of phenalenyl, such as cyclazine and heptazine, have long been known to possess a negative singlet-triplet gap, $\Delta E_{ST}=E(S_{1})-E(T_{1})$. Using the well-known Pariser-Parr-Pople (PPP) model, a semi-empirical, wave-function-based
Hamiltonian for correlated $\pi$-electrons, we investigate the singlet-triplet gap in ten N-substituted phenalenyl motifs. Two schemes of long-range Coulomb interactions are considered, and key parameters, including the on-site orbital energy, Hubbard U, and hopping integrals, are systematically tuned to
benchmark the model for reliably estimating negative singlet-triplet gaps. Full configuration-interaction (FCI) method is employed to incorporate electron-correlation effects. Ground-state and $T_{1}$ absorption spectra are subsequently calculated using the optimized PPP parameters that best reproduce the available experimental data. For validation, first-principles TDDFT calculations using various exchange–correlation functionals are also performed. Conventional adiabatic TDDFT fails to reproduce the inverted ($S_{1}-T_{1}$) ordering, indicating that the inclusion of the correlation driven multiconfigurational effects are essential for describing it. We find that the singlet TDDFT ground-state absorption spectra reproduce several qualitative features of the PPP-FCI spectra, although the TDDFT excitation energies are systematically higher. Detailed analysis of the ground-state and $T_{1}$ absorption spectra reveals significant configuration mixing, providing a comprehensive characterization of the optical response of the N-substituted phenalenyl derivatives studied.
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Materials Science
Towards Extended Active Learning for Modelling Ferroelectric Switching: the Need for 'Gold Standards'
Jeffrey R. Reimers, Wenbin Zhang, Zhe Su et al. (+4 more)
For the purpose of modelling ferroelectric switching in wurtzite-structured materials, four cost-effective density-functional theory (DFT) methods (PBE, PBEsol, r2SCAN, and r2SCAN-rVV10) are considered and compared to various ab initio approaches based on the random-phase approximation (RPA), including RPA with singles corrections (RPAR+S), as well as second-order Møller-Plesset perturbation theory (MP2). The purpose is to determine whether an ab initio approach could act as a 'gold standard' for estimating the reliability of DFT, thus determining an optimal DFT method for use in exhaustive tasks such as the training of machine-learning interatomic potentials (MLIP) for large-scale simulations of materials of arbitrary composition and structure such as Al1-xScxN and Zn1-xMgxO, using AlN, Al0.5Sc0.5N, ZnO, and Zn0.5Mg0.5O as model materials. Applications of active learning (AL) are now common, in which results from MLIP simulations are used to enhance the DFT training data set, but future extended active learning (EAL) methods will also need to systematically assess the DFT methodology against a gold standard. Herein, the variability of the ab initio results is found to exceed that required for a robust gold standard, but the DFT and ab initio approaches appear to converge on RPAR+S and r2SCAN-rVV10 as optimal method choices to initiate EAL. The electron correlation energy is found to be dominated by covalent binding effects associated with the high-electron-density anions involved, but the van der Waals dispersion force is seen to be too significant to ignore in ferroelectric modelling.
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All authors Jeffrey R. Reimers, Wenbin Zhang, Zhe Su, Musen Li, Carla Verdi, Tim Gould, Wei Ren
Materials Science · Cross-listed from cond-mat.mes-hall
Detecting a large magneto-optical shift in Py/NiO bilayers
Adrielson Dias, Maria Clara, Ozéas Rodrigues et al. (+3 more)
Here, magneto-optical magnetometry measurements on Py/NiO bilayers reveal a pronounced
magnetic-field-induced wavelength shift, demonstrating strong magneto-optical coupling in this antiferromagnetic system. A systematic and monotonic spectral shift of up to ~ 400 nm is observed as the applied
magnetic field increases, saturating at higher fields. Quantitative analysis shows that the associated magneto-optical energy variation is on the order of 107 eV, comparable to the
magnon energy scale in NiO. Owing to the large NiO thickness, the observed effect originates from
magnons intrinsic to the antiferromagnetic NiO layer rather than from
spin currents injected by the Py underlayer. These results provide direct experimental evidence for
magnetic-field control of antiferromagnetic
magnon energies via magneto-optical interactions, establishing Py/NiO bilayers as a promising platform for optically probing and manipulating antiferromagnetic
spin dynamics.
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All authors Adrielson Dias, Maria Clara, Ozéas Rodrigues, Gabriel Henrique, José Lucas, José Holanda
Materials Science · Cross-listed from cond-mat.mes-hall
Resonantly Enhanced Phonon Transport by Magnon Pumping in a Ferromagnetic/Piezoelectric Bilayer
André José, Carlos Eduardo, Adrielson Dias et al. (+2 more)
We report the first experimental observation of resonantly enhanced propagating
phonon transport induced by
magnon pumping in a ferromagnetic/piezoelectric bilayer. Surface acoustic waves (SAWs) generated in a 128$^{\circ}$ Y-cut LiNbO$_3$ delay-line device resonantly excite magnetization dynamics in an adjacent Co film through magnetoelastic coupling. The enhancement of the transmitted acoustic signal occurs exclusively when the SAW frequency satisfies the ferromagnetic resonance condition predicted by the Kittel dispersion, providing a direct experimental fingerprint of resonant
magnon-
phonon coupling. A systematic comparison between the Co/LiNbO$_3$ bilayer and the bare LiNbO$_3$ substrate demonstrates that the observed transmission enhancement originates solely from the dynamic interaction between propagating
phonons and coherent magnetization precession. Furthermore, measurements performed at different SAW harmonics reveal that only the harmonic satisfying the FMR condition produces a measurable enhancement, confirming the frequency-selective nature of the phenomenon. These findings establish an efficient mechanism for transferring energy from
magnons to propagating
phonons and provide a new strategy for actively controlling coherent acoustic transport in hybrid spintronic, straintronic, and
quantum phononic platforms.
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All authors André José, Carlos Eduardo, Adrielson Dias, José Araújo, José Holanda
Materials Science · Cross-listed from cs.LG
An open benchmark for machine learning-based polymer property prediction
Robert W. Learsch, Nicholas Liesen, Daniel S. Levine et al. (+2 more)
Polymer property prediction lacks open, standardized
benchmarks that enable rigorous comparison of machine-learning methods, with existing resources covering only a narrow fraction of
polymer architectures, such as homopolymers. We introduce
Polymer Benchmark 2026 (PolyBench26), an open
dataset comprising nearly 250,000
polymer-property datapoints across eight physical properties, including data from experimental measurements, density functional theory, and molecular dynamics. The
benchmark supports four evaluation tasks across homopolymers and alternating, random, and block copolymers: in-distribution property prediction,
dataset-size scaling, repeat-unit complexity, and transfer to held-out
polymer architectures. We compare
language model, graph-based, and descriptor-based approaches and find graph-based models provide the lowest errors in property prediction, retain their advantage across the evaluated training-set sizes, and remain robust to increasing repeat-unit complexity. PolyBench26 provides a reproducible foundation for developing models for the increasingly complex
polymer design space. The PolyBench26
benchmark is available open-source at https://github.com/rlearsch/PolymerBenchmark2026.
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All authors Robert W. Learsch, Nicholas Liesen, Daniel S. Levine, Anna M. Hiszpanski, Evan R. Antoniuk
Materials Science · Cross-listed from physics.chem-ph
First-Principles Nonadiabatic Dynamics via the Multi-Orbital Anderson-Newns Model
Liwen Ko and Joonho Lee
We develop a first-principles theory for nonadiabatic surface dynamics, providing a fit-free connection between density functional theory (DFT) calculations and the effective multi-orbital Anderson-Newns (AN) theory. Our theory contains two main advances. First, we outline the multi-orbital AN theory with orbital overlap and derive closed-form expressions for the hybridization energy, electronic dynamics, and electronic friction. Second, we describe a procedure to map the DFT
Hamiltonian into the effective AN
Hamiltonian with nuclear-position dependence. We obtain the electronic part of the AN
Hamiltonian solely from the adsorbate-projected density-of-states
matrix. We then define the bare nuclear potential as the difference between the total energy and the hybridization energy. The theory is applied to H and CO on the Cu surface, where widely used assumptions about the hybridization function, including the wide-band limit, semi-elliptical forms, and separability in energy and nuclear coordinate, are found to fail, and the single-orbital description breaks down qualitatively for CO. We expect this work to be broadly useful for first-principles modeling of coupled nuclear-electronic dynamics and chemical reactions at metallic surfaces.
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Materials Science · Cross-listed from cond-mat.soft
Control of filament network rigidity by the condensation of crowding molecules
Jiyong Cheon, Zhengyan Lin, Dean Kim et al. (+2 more)
Understanding how
liquid-
liquid phase separation impacts the mechanics of filament networks is a fundamental physical problem at the heart of biological cellular processes and soft material design. While a few theoretical mechanisms have been proposed, a clear demonstration of the direct coupling of phase separation to the overall network stiffness is missing. We report experiments that reveal a universal mechanism by which the condensation of macromolecular crowders induces a rigidity transition in a model filament network. We reconstituted stiff sterically interacting helical filaments and polymeric crowders. Initially, the macromolecules were uniformly dissolved and the filaments formed bundles that assembled a rigid entangled network. Once the crowders condensed into droplets, the network structure lost its rigidity and its mechanical response weakened by an order-of-magnitude. The subsequent dissolution of the condensates was accompanied by the re-establishment of rigidity. Our results show that crowder phase separation modulates the mechanics of filament networks by tuning the osmotic pressure holding the network together. This principle may serve as a paradigm for devising dynamically tunable filamentous materials.
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All authors Jiyong Cheon, Zhengyan Lin, Dean Kim, Anirudh Malli, Itamar Kolvin
Materials Science
Suppressed Defect Emission and Enhanced Blue Luminescence of Zn-Doped CuBr Quantum Dots synthesized in Room-Temperature Synthesis
Aryamol Stephen, Ruchi Kumari, Saparja Roy et al. (+3 more)
Deep-blue-emitting CuBr
quantum dots (QDs) hold promise as nontoxic and heavy-metal-free optoelectronic materials, yet their efficiency is limited by intrinsic defects. We report Zn doping as an effective strategy to mitigate defect-mediated recombination in CuBr QDs synthesized via an eco-friendly supersaturated recrystallization method under ambient conditions. XRD shows
lattice contraction, Rietveld refinement confirms substitutional doping, and XPS verifies Cu$^+$/ Zn$^{2+}$ states without secondary phases. HR-TEM analysis reveals uniform 3.46 $\pm$ 0.12 nm Zn:CuBr QDs with reduced bandgap, after doping, indicating weaker
quantum confinement. The dominant emission peaks appear at 406 nm ($Z_f$) and 431 nm ($Z_{1,2}$) under 365 nm excitation. Narrows defect FWHM, elevated band-edge emission, and extends carrier lifetimes, achieving 96.4 % color purity with CIE coordinates (0.1520, 0.0395). These findings demonstrate that Zn doping is a simple, scalable, and environmentally benign strategy for engineering efficient blue-emitting CuBr QDs.
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All authors Aryamol Stephen, Ruchi Kumari, Saparja Roy, P. Jayaram, A. Biju, P. M. Sarun
Materials Science
Three-Dimensional Imaging of High-Density Dislocation Networks and Their Interactions using Multislice Electron Ptychography
Eegene Chung, Anand Ithepalli, Naomi Pieczulewski et al. (+6 more)
Development of novel devices often involve combining functional materials and substrates, each chosen for particular physical properties such as low-loss or thermal conductivity. This, however, can introduce a large
lattice mismatch and high density of structural defects that may limit device performance and reliability by trapping charge or creating leakage pathways. Such is the case for integrating superconducting TiN with a low-loss sapphire substrate. Here we resolve and image the resulting misfit, screw, and threading dislocations in epitaxial TiN on sapphire using the depth-sectioning capabilities of multislice electron ptychography. We find misfit dislocations spaced ~1.6 nm apart and track out-of-plane crossings of misfit dislocations as well as their transitions to threading dislocations, details which are obscured in conventional defect-imaging methods. The ability to correlate specific dislocation types and their interactions in extremely small volumes and at high densities is valuable for understanding structure-property relations even in modern, scaled devices.
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All authors Eegene Chung, Anand Ithepalli, Naomi Pieczulewski, Chia-Hao Lee, Steven Zeltmann, Keun-Yeol Park, Celesta S. Chang, Debdeep Jena, David A. Muller
Materials Science · Cross-listed from cond-mat.mes-hall
Nonlinear Spin Polarization Enables Néel Order Switching in Centrosymmetric Altermagnets
Sunit Das, Sayan Sarkar and Amit Agarwal
Deterministic electrical switching of the Néel order remains challenging in centrosymmetric altermagnets, where linear current-induced
spin polarization is forbidden by inversion
symmetry. Here, we establish a nonlinear route to Néel order control.
Spin group
symmetry shows that, in the nonrelativistic limit, the nonlinear
spin polarization is constrained along the Néel vector, with a staggered response allowed in $8$ of the $10$ nontrivial
spin-Laue groups. Although this Néel
spin polarization is torque-inactive by itself, finite
spin-orbit coupling can generate an additional uniform component transverse to the Néel vector. Using a minimal model for the $d$-wave altermagnet FeSb$_2$, we demonstrate the coexistence of the nonrelativistic staggered response with an SOC-induced uniform transverse component. Landau-Lifshitz-Gilbert equation-based macro-
spin simulations reveal that the transverse component alone produces oscillatory dynamics, whereas its cooperative action with the staggered response enables deterministic $180^\circ$ reversal. We further show that changing the electric field orientation reverses the staggered
spin response and selects the switching direction, while the opposite Néel states can be distinguished by their anomalous Hall response. Our results establish a nonlinear electrical write-read scheme for centrosymmetric altermagnets.
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Materials Science
Disentangling Surface Charge and Electrolyte Effects on Interfacial Water at Electrified Pt(111)
Thorben Eggert, Lang Li, Yair Litman et al. (+3 more)
The structure of interfacial water at electrified metal electrodes is known to affect electrocatalysis, and experiments highlight its sensitivity to electrolyte ion identity and applied bias. To disentangle generic charge-controlled structural changes from ion-specific effects, we compare ab initio molecular dynamics water structures at electrified Pt(111) generated with two very different biasing schemes: an explicit ion imbalance in the double layer and homogeneously distributed partially charged hydrogen atoms. Despite these distinct counter-charge representations, both approaches yield a consistent average response of the first water bilayer, in particular of the chemisorbed first layer, when compared on a common surface-charge scale. Method-dependent differences, in particular those associated with explicit electrolyte ions, become apparent only in more local structural descriptors. The hydrogen-bond
topology reveals charge-dependent chain-to-ring rearrangements, with explicit ions enhancing ring populations near the potential of zero charge. Layer-resolved vibrational density of states (VDOS) assigns the strongest O-H stretching perturbation to chemisorbed first-layer water and identifies high-frequency signatures of ion-coordinated water, while computed vibrational sum-frequency generation (VSFG) spectra show that the physisorbed, electrolyte-facing region is particularly sensitive to the counter-charge representation. These results suggest that surface charge controls the average structural response, whereas electrolyte ions and their solvation shells become visible only when locally refined descriptors are investigated or probed, e.g. the H-bond network
topology and vibrational fingerprints of the interfacial bilayer.
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All authors Thorben Eggert, Lang Li, Yair Litman, Karsten Reuter, Nicolas G.Hoermann, Clotilde S. Cucinotta
Materials Science
Agent-E2MD: Autonomous Translation of Interatomic Potential Equations into Physically Validated Pair Styles for Molecular Dynamics in LAMMPS
Bilvin Varughese, Orcun Yildiz, Aditya Koneru et al. (+3 more)
Interatomic potentials underpin MD and govern predictive atomistic-model fidelity for metals,
semiconductors, oxides,
liquids, and reactive systems. A potential has limited practical value until reliably implemented in production MD code. Slow, expertise-intensive implementation requires more than equation-to-C++ translation: it must select the neighbor-list architecture, evaluate and distribute many-body derivatives, manage interprocessor communication, and preserve host-code energy, force, and virial conventions. We introduce
Agent-E2MD, a knowledge-guided agentic workflow that translates user-specified interatomic models into executable LAMMPS pair styles. It combines architectural classification, code generation, autonomous build-test-fix cycles, simulation execution, and hierarchical physical validation. We test
Agent-E2MD on seven material-potential pairs: Lennard–Jones Ar, EAM/FS Ag, MEAM Bi, Tersoff Si, GAP Ni, ReaxFF C/H/N/O, and a recently developed Symbolic Regression EAM (Symb EAM) model for Al, currently unavailable in LAMMPS. Single-point results match reference energies and forces for all seven models. Five crystalline many-body
benchmarks recover reference relaxed
lattice properties, vacancy formation energies, and elastic constants. Ag, Bi, Si, and Ni are stable at finite temperature in nanosecond-scale simulations; ReaxFF extends validation to reactive dynamics with evolving bond order and charge equilibration. Results demonstrate that the software architecture for an interatomic potential can be inferred from its physical and mathematical structure.
Agent-E2MD does not replace scientific judgment; it shifts users' effort from routine implementation to model definition, rigorous validation, and physical interpretation. The framework provides a practical, traceable bridge between emerging AI-driven potential discovery methods and production-scale atomistic simulations.
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All authors Bilvin Varughese, Orcun Yildiz, Aditya Koneru, Henry Chan, Tom Peterka, Subramanian Sankaranarayanan
Materials Science · Cross-listed from cond-mat.str-el
Tilt-controlled Drude anisotropy in nodal-line semimetals: logarithmic enhancement, interband correction, gauge consistency, and the Landau-damping window
Wei Li and Jing-Rong Wang
We study the anisotropic charge response of a three-dimensional tilted nodal-line semimetal in which the tilt enters the spectrum through an identity term and acts as the model control parameter. Using the Kubo formula with line-integral vertices, we show that the tilt-induced deformation of the low-energy phase space produces parametrically different longitudinal and transverse Drude responses: the longitudinal weight grows logarithmically as $D_{zz}=B\ln(1/\delta)$ with the analytically determined coefficient $B=g/(2\pi)^2$—within the window in which the Fermi-surface tail lies inside the ultraviolet cutoff, while at a fixed physical cutoff the weight saturates instead at a cutoff-set plateau—whereas the transverse weight follows a stronger algebraic scaling $D_\perp\sim\delta^{-1}$; the leading $\sqrt\delta$ corrections to both asymptotic forms are obtained analytically. The interband polarization retains the $q^2$ long-wavelength structure, with a coefficient that is infrared-integrable through Pauli blocking at finite doping yet carries a slow ultraviolet logarithm; it renormalizes the collective mode multiplicatively and sets the interband absorption threshold $\omega_c=2\mu/(1+|\eta_z|)$. A self-consistent solution of the plasmon dispersion identifies a tilt-dependent damping-free window bounded by the interband continuum. We predict that the type-II extension of this window, within the stated bandwidth (Brillouin-zone-like) cutoff regularization, contains a candidate low-frequency acoustic-like branch outside the particle–hole continua for $\eta_z\gtrsim1.2$ over a finite window in momentum transfer.
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Materials Science · Cross-listed from cond-mat.str-el
Crystal Electric Field Analysis on the Magnetic Properties of Ferromagnetic CeRu$_2$Ge$_2$ Single Crystal
Shovan Dan, Suman Nandi, Gourav Dwari et al. (+5 more)
We report a detailed anisotropic studies on the
magnetic and transport properties of a CeRu$_2$Ge$_2$ single
crystal. A clear ferromagnetic transition is observed at $T_{\rm C} = 7.5$~K in the
magnetic susceptibility, electrical resistivity and heat capacity measurements. The magnetoresistance (MR) is positive at low temperature within the magnetically ordered state. We confirmed the presence of a
magnon excitation gap in the resistivity, MR and the low temperature heat capacity data. The pronounced anisotropy observed in the
magnetic susceptibility and magnetization along the [100] and [001] directions is quantitatively explained within the
crystal electric field (CEF) framework using the point-charge model. The analysis reveals a CEF level scheme comprising three doublets, with a ground state and two excited states at 491 and 671~K, that was further confirmed from the Schottky effect in the
magnetic part of the heat capacity data. Unlike most Kondo
lattice ferromagnets of Ce compounds, where the
magnetic easy axis deviates from the expected CEF ground state, CeRu$_2$Ge$_2$ exhibits magnetization, which is fully consistent with the CEF derived ground state wave function, with the easy axis of magnetization aligned along the [001] direction.
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All authors Shovan Dan, Suman Nandi, Gourav Dwari, Bishal Baran Maity, Bhagyashree A Chalke, Ruta Kulkarni, P. D. Babu, Arumugam Thamizhavel
Materials Science
Microstructure, tensile behavior and cyclic bendability of directly extruded biodegradable Zn, Zn-Mg and Zn-Mg-Sr wires
L. Hlodák, K. Tesař, M. Lebeda et al. (+5 more)
Zinc-based
alloys are promising biodegradable implants, yet the trade-off between strength, ductility, and bendability in thin-wire form remains poorly understood. To address this, pure Zn (PZ), Zn-0.15Mg (ZM), and Zn-0.8Mg-0.2Sr (ZMS) wires of ~290 um diameter were produced by direct extrusion, and their microstructure, texture, tensile, and bending behavior were characterized. Mg2Zn11 and SrZn13 phases promoted particle-stimulated nucleation, refining the grain size from 35.8 um in PZ to 6.8 and 3.3 um in ZM and ZMS, respectively, weakening the basal-fiber texture, and raising the ultimate tensile strength at 37 {\deg}C from about 119 MPa for PZ to 291 and 334 MPa for ZM and ZMS, respectively. PZ deformed through twin transmission across weakly misoriented grains, producing serrated stress drops in tensile curves, with further straining accommodated by non-basal slip. ZM showed a single, aging-sensitive stress drop from localized twin nucleation and particle cracking, while ZMS showed distributed particle cracking without associated stress drops, consistent with its higher elongation to failure of 19 % at 37 {\deg}C. Mechanical properties remained broadly stable after 20 days of aging at 37 {\deg}C, with no measurable change in the nanoscale precipitates after 7 days. All compositions, however, showed markedly poor cyclic bendability accompanied by a twinning-detwinning mechanism directly observed by EBSD for the first time in zinc. These results establish single-step direct extrusion as a viable route to strong, fine-grained biodegradable Zn wires, while identifying poor bendability as the principal obstacle to bending-critical biomedical devices.
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All authors L. Hlodák, K. Tesař, M. Lebeda, J. Duchoň, J. Kubásek, J. Čech, A. Školáková, J. Pinc
Materials Science
Superfluorescence as a cooperative amplifier of hidden anisotropy in a ferroelectric hybrid perovskite
Changhao Gao, Daniel Sandner, Talia Ruhrberg Estévez et al. (+4 more)
Superfluorescence (SF), intense picosecond bursts from self-synchronizing dipoles, is promising for room-temperature
quantum sources. Yet, whether this synchronization can convert weak structural anisotropies into robust macroscopic order remains an open question. Here, we demonstrate that polycrystalline ferroelectric 2D perovskite thin films exhibit strongly linearly polarized SF with a degree of polarization (DOP) up to 86%. Remarkably, macroscopic polarization emerges without external bias despite randomly oriented microscopic domains, suggesting a cooperative gain mechanism that amplifies weak local anisotropies by several orders of magnitude into coherent, linearly polarized light bursts. Our results establish cooperative superfluorescence as a general concept for translating microscopic anisotropy into robust macroscopic order, exemplified here for linear polarization, offering a sensitive probe of hidden material
symmetries and a framework for polarized
quantum light sources
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All authors Changhao Gao, Daniel Sandner, Talia Ruhrberg Estévez, Jeron Timmer, Sophia Klubertz, Martijn Kemerink, Felix Deschler
Materials Science
Topology-Stratified Materials Discovery with A Flow-Based Generative Model
Jingyi Zhou, Oyshee Chowdhury, Noah Oyeniran et al. (+1 more)
Accurate generation of
crystal structures is the foundation to the discovery of high-performance materials for extreme-environment applications, such as aerospace, additive manufacturing, and fusion energy systems. Although generative modeling has emerged as a promising approach for
crystal design, its performance remains limited by the complex
crystal structures and diverse chemical compositions. In this work, we develop UFO-MGen, a universal flow-based generative model that learns topological features of Wyckoff representations and leverages this information to accurately generate
crystals across vast structural and chemical spaces. Compared with state-of-the-art generative models, UFO-MGen achieves the highest
crystal generation success rate under a rigorous multi-stability evaluation framework, the highest SUN (stable, unique, novel) rate, and a remarkable extrapolation capability that has not been reported by previous models. Furthermore, a fine-tuning module is implemented to UFO-MGen for property-constrained
crystal generation, enabling the inverse materials design toward target properties. The UFO-MGen opens a new avenue for accelerated materials discovery and providing a foundation for universal materials intelligence.
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All authors Jingyi Zhou, Oyshee Chowdhury, Noah Oyeniran, Chongze Hu
Materials Science
Deep Generative Crystal Structure Prediction: A Benchmark Study and a Controlled Test of Prototype Dependence
Lai Wei, Rongzhi Dong, Ying Feng et al. (+2 more)
Deep generative models are widely reported to enable de novo
crystal structure prediction (CSP), but their capability has not been measured consistently against template-based methods. We evaluate 12 representative generative CSP models, spanning latent-variable,
diffusion, flow-matching, autoregressive, and
manifold random-walk architectures, against TCSP 2.0 on 180 test structures and a leakage-controlled subset of 46. All methods use identical structure-matching,
symmetry, and consensus criteria. Template
retrieval is the strongest single method, reaching 68.3% top-1 success;
symmetry-aware EquiCSP (66.4%) and Uni-3DAR (62.9%) form the next tier. However, comparison with TCSP 2.0 shows that most structures correctly predicted by generative models are also correctly predicted by template substitution. Thus, the set of structures uniquely reachable by generation is small, limiting its practical advantage for discovering structures outside existing prototype libraries. To test the source of this performance, we removed entire stoichiometric prototype families from the training set and retrained the strongest generative model. Accuracy declined by 50-78% across four families, establishing that performance is substantially prototype-dependent. A small minority of structures survived removal of their prototype family, demonstrating a real but limited
retrieval-independent predictive capacity. Present generative CSP models therefore function largely as implicit, softer-edged prototype libraries rather than genuinely de novo predictors. Enlarging this residual capacity, rather than aggregate match rate alone, is the central open problem.
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All authors Lai Wei, Rongzhi Dong, Ying Feng, Madeline Miklos, Jianjun Hu
Materials Science
Observation of the Nernst effect driven by longitudinal spin fluctuations
Fuyuki Ando, Hiroto Adachi, Hossein Sepehri-Amin et al. (+3 more)
The Nernst effect, which converts a heat current into a charge current in the orthogonal direction, is generally classified into the ordinary effect due to an external
magnetic field applied to conductors and the anomalous effect due to static magnetization in
magnetic materials. Thus, one expects that the anomalous Nernst effect disappears at the Curie temperature following the magnetization. Here, we observe the Nernst effect which rather manifests around the Curie temperature. In a series of ferromagnetic (Mn,Cr)Sb samples, the Nernst coefficients exhibit finite values even across the Curie temperatures, whereas the anomalous Hall resistivity disappears, suggesting the breakdown of the Mott relation. These surviving Nernst and vanishing Hall effects result in a peak behavior of the transverse thermoelectric conductivity around the Curie temperature, which we theoretically reproduce by introducing longitudinal fluctuations of
spins without accounting for an exotic
spin texture, a non-trivial electronic structure, or
magnon- and
phonon-drag effects. The Nernst effect driven by the longitudinal
spin fluctuations reveals that not only the static
magnetic order but also the
spin fluctuations can be a driving force of the Nernst effect in
magnetic materials, opening another way for boosting transverse thermoelectric conversion.
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All authors Fuyuki Ando, Hiroto Adachi, Hossein Sepehri-Amin, Takamasa Hirai, Keisuke Hirata, Ken-ichi Uchida
Materials Science
Surface-bulk hybridization enhances the Berry curvature dipole in GaAs(110)
Gastón Blatter, Jorge I. Facio and Jeroen van den Brink
Symmetry breaking at crystalline boundaries can enable electronic responses that are forbidden in the bulk. Here, we investigate the Berry
curvature dipole (BCD) at GaAs(110) surfaces using first-principles calculations. While the BCD vanishes in bulk GaAs due to
symmetry constraints, the reduced surface
symmetry permits a finite dipole. We show that surface relaxation promotes hybridization between bulk and surface states, which strongly influences the surface BCD. Specifically, in unrelaxed slabs, the BCD arises predominantly from interband coupling among exponentially localized surface states lying within the projected bulk band gap. Surface relaxation shifts these states into the energy range of the bulk continuum, transforming them into surface resonances and promoting hybridization with bulk-like states. This hybridization generates pronounced Berry-
curvature hot spots, resulting in an overall enhancement of the BCD. Our results highlight the importance of surface relaxation for accurately describing surface–bulk hybridization, which in turn plays a key role in Berry-
curvature-driven responses at crystalline boundaries.
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Materials Science
Intrinsic switching leads to oxygen diffusion and breakdown in hafnia ferroelectrics
Xabier Diaz de Cerio, Iñigo Robredo-Magro and Jorge Íñiguez-González
Conventional ferroelectrics exhibit well-defined polarization states linked through electric switching. In fluorite-structured ferroelectrics like hafnia, though, switching and oxygen
diffusion seem to coexist, enriching the nature of ferroelectricity. Here we address the intrinsic, room-temperature switching and
diffusion kinetics of hafnia ferroelectrics using machine-learning molecular dynamics. We identify two distinct switching mechanisms that are both active at realistic time scales. Critically, our simulations reveal that, because the
lattice does not dissipate fast enough the heat originating from localized switching events, these two processes concatenate in an avalanche-like manner leading to oxygen conduction. Our results thus show that intrinsic switching leads to breakdown in hafnia ferroelectrics. They also suggest how this outcome might be avoided through suitably designed field pulses.
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