Materials Science · Cross-listed from cond-mat.soft
Theory of distribution skewness effect on polydisperse random close packing
Vinay Vaibhav, Carmine Anzivino and Alessio Zaccone
We investigate the random close packing density, $\phi_\textrm{RCP}$, of polydisperse hard sphere systems using a theoretical framework based on the
equilibrium model of crowding. We derive a closed-form solution for $\phi_\textrm{RCP}$ in terms of the moments of the diameter distribution, enabling an analytical exploration of the effects of polydispersity ($\delta$) and skewness ($S$) on packing density. For a binary mixture, it is possible to explore a broader range of dependence of $\phi_\textrm{RCP}$ on $\delta$ for a given $S$ or on $S$ for a given $\delta$. We show that the dependencies of $\phi_\textrm{RCP}$ on skewness for a variety of continuous distributions collapse onto a theoretical master curve obtained for the binary mixture case. By correcting the theory so that it obeys known exact limiting behaviours for extreme size asymmetry, our analytical predictions not only agree with previously obtained numerical results, but also predict previously unexplored regions of the $\phi_\textrm{RCP}$ parameter space.
Read the full abstract ▾
Materials Science
Composition-dependent Thin-film Synthesis of Layered Ternary Iron Nitrides FeMN2 (M = W, Mo)
Baptiste Julien, Yuwei Yang, Liam A. V. Nagle-Cocco et al. (+3 more)
Ternary transition-metal nitrides with layered
crystal structure host anisotropic bonding and reduced dimensionality that may lead unconventional electronic and
magnetic behavior. The synthesis of these layered nitrides phases in thin-film form is difficult because reactive sputtering often favors metastable rocksalt-derived structures. Here we report the composition-dependent thin-film synthesis and characterization of structure and properties of layered ternary iron nitrides FeMN2 (M = W, Mo) with triangular Fe sublattice, prepared by reactive sputtering of amorphous precursors and post-deposition ammonia (NH3) annealing that staggers atomic mixing of the element precursors and long-range crystallization of extended structure. We find that FeWN2 maintains good phase purity across a broad composition range indicative of cation substitution in the layered structure, while FeMoN2 only shows good phase purity in Fe-poor composition, with an optimum corresponding to Fe0.8Mo1.2N2 stoichiometry. Azimuthal grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis shows that in both material systems, Fe-rich films exhibit strong out-of-plane fiber textures, and synchrotron X-ray absorption spectroscopy (XAS) provides insight into local Fe state and environment in both material systems. Room-temperature magnetization measurements of FeWN2 reveal that while the stoichiometric film shows a simple paramagnetic behavior, the Fe-poor films are weakly
ferromagnetic. Together, these results suggest that off-stoichiometry and local disorder within the triangular Fe sublattice may partially relieve
magnetic frustration in the layered framework, and highlight the strong coupling between composition, microstructure, and
magnetic properties in layered nitride materials.
Read the full abstract ▾
All authors Baptiste Julien, Yuwei Yang, Liam A. V. Nagle-Cocco, Nicholas A. Strange, Nicholas M. Bedford, Andriy Zakutayev
Materials Science · Cross-listed from cond-mat.mes-hall
Carrier-coupled ultrafast structural dynamics and interlayer energy transport of supported transition metal dichalcogenide heterostructures
Md. Shaikot Alam Shakil, Ting-Hsuan Wu, Xing He et al. (+5 more)
Understanding the electronic coupling and energy flow across layered two-dimensional
heterostructures (HSs) is crucial to the exploitation of carrier and
phonon transports as well as thermal management in next-generation optoelectronic devices. By using reflection ultrafast electron diffraction, we directly examine photoinduced out-of-plane structural dynamics of supported MoS2/WS2
bilayer HSs and their individual monolayers. Experimental evidence reveals the launch of ultrafast carrier-coupled intralayer atomic motions due to interlayer charge transfer across the van der Waals (vdW) heterojunctions that is absent for individual monolayers. Such a notable carrier-
lattice correlation is in addition to the electronic coupling manifested in the enhanced optical absorption for HSs. Also, different pathways of energy flow as a result of carrier-
phonon coupling and
phonon scattering are reported with the corresponding characteristic times. On longer timescales, relaxation of thermalized atomic motions can be sufficiently described by a thermal transport model. A higher thermal boundary conductance (TBC) across MoS2/WS2 HSs is obtained compared to those at the monolayer-substrate interfaces; however, the similar TBC values suggest comparable couplings of
phonons across vdW contacts. These results further shed light on the optical,
phonon, and interfacial thermal properties of vertically-stacked vdW HSs.
Read the full abstract ▾
All authors Md. Shaikot Alam Shakil, Ting-Hsuan Wu, Xing He, Abu Montakim Tareq, Zhenjia Zhou, Libo Gao, Naihao Chiang, Ding-Shyue Yang
Materials Science
Towards exascale fully relativistic pseudopotential density functional theory calculations enabled by mixed-precision computation and compressed-communication using residual based subspace iteration
Nikhil Kodali, Gourab Panigrahi, Nishant Gupta et al. (+6 more)
Materials exhibiting noncollinear magnetism or strong
spin-orbit-coupling underpin many spintronic and topological applications, but their simulations require complex two-component spinors and costs substantially more than scalar density functional theory (DFT). We present a GPU-centric exascale finite-element DFT framework with noncollinear magnetism and
spin-orbit-coupling, combining (i) adaptive higher-order finite-element discretization, (ii) a
matrix-free Poisson solver, (iii) residual-based Chebyshev filtered subspace iteration (R-ChFSI) for sparse generalized eigenproblems, (iv) R-ChFSI-enabled mixed precision computation with block floating-point compressed MPI communication, and (v) communication-efficient band partitioning. R-ChFSI permits inexact
matrix-multivector products and $4\times$–$6.4\times$ compression of communicated data relative to FP64 while preserving double-precision robustness and reducing computation and data movement. Results demonstrate strong scaling on Aurora and Frontier, with up to $3.4\times$ faster Chebyshev filtering. On Aurora, total self-consistent-field (SCF) solve wall time reduces by $2\times$. An 800-node (9,600-GPU) calculation demonstrates fully relativistic pseudopotential DFT for $\sim$80,000 electrons in under 7 minutes per SCF iteration.
Read the full abstract ▾
All authors Nikhil Kodali, Gourab Panigrahi, Nishant Gupta, Kartick Ramakrishnan, Sundaresan G, Rudra Panch, Sambit Das, Vishwas Rao, Phani Motamarri
Materials Science · Cross-listed from cond-mat.mes-hall
Surface Originated Cross-Field Anomalous Transport in Magnetoelectric Multilayers
Jin Cao, Wei Du, Xue-Jin Zhang et al. (+3 more)
In material systems with slab geometry, the surface contribution to physical responses is commonly expected to diminish rapidly with increasing thickness, giving way to the bulk response. Here, we show that this conventional wisdom is violated in a class of gate-induced responses, including gate-induced orbital and
spin magnetization as well as cross-field anomalous thermoelectric transport. We develop a general framework for these effects, which naturally decomposes the total response into surface- and bulk-contributions treated on equal footing. Remarkably, the volume-averaged surface contribution remains finite in the thick-slab limit and exhibits the same thickness scaling as the bulk term. Furthermore, the surface response originates from band
geometric quantities distinct from those in the bulk, being constrained solely by surface
symmetries. As a result, it can dominate the overall response when the bulk contribution is
symmetry-forbidden. Taking MnBi$_2$Te$_4$ multilayers as an example, we predict a strong surface-dominated cross-field anomalous Nernst effect arising from surface Berry
curvature, which is readily accessible to experimental detection. These findings reveal a previously overlooked significance of surface response and open a new direction in the study of surface
quantum geometry.
Read the full abstract ▾
All authors Jin Cao, Wei Du, Xue-Jin Zhang, Cong Xiao, Qian Niu, Shengyuan A. Yang
Materials Science
Hysteretic phononic band structures arising from martensitic phase transformations
R. Esquivel-Sirvent, B. Manzanares-Martínez and J. Manzanares-Martínez
Thermal tuning of phononic
crystals typically treats each constituent's elastic modulus as a single-valued function of temperature. Here we show that when one constituent undergoes a first-order martensitic transformation (NiTiCu), paired with a Parylene C spacer in a thin one-dimensional composite rod, the intrinsic thermal hysteresis of the transformation is transferred to the collective acoustic response, making it depend on thermal history. Transfer-
matrix calculations performed separately along the heating and cooling branches reveal that the same temperature within the transformation interval can correspond to two distinct Bloch band structures and two distinct transmission spectra. As temperature is cycled, stop-band edges trace closed loops in the temperature-frequency plane, producing hysteretic phononic band structures. At a fixed probe frequency, the rod can switch between transmitting and strongly attenuating states depending solely on whether the sample was last heated or cooled, with transmission contrasts exceeding 50 dB in a six-
cell structure, thereby realizing a form of acoustic
memory. The filling fraction of the active segment provides an independent
geometric control parameter that modifies the width of the hysteresis loops and the positions of gap closures. These predictions can be tested directly using immersion-ultrasonic measurements on NiTiCu/Parylene C composite rods.
Read the full abstract ▾
Materials Science
Magnetic precession induced spin accumulation in collinear antiferromagnets
Q. Xue and J. Zhou
Generating and characterizing uniform and staggered
spin polarization in antiferromagnets is one of the key challenges for
antiferromagnetic spintronic technology. Here, we perform perturbative theory, group-theoretical
symmetry analysis, low energy and ab initio simulations to propose that the
magnetic precession near the
equilibrium magnetic axis could generate finite uniform and staggered
spin polarization at the opposite
magnetic sublattices (referring to total
magnetic and Néel vector generation) in a single AFM
semiconductors. This response does not require the heterojunction setup and could eliminate the
lattice mismatch issues at the junction. Through scrutinizing all symmetrically-protected vanishing
magnetic moment groups and especially focusing on parity-time (PT ) invariant groups, we identify the
symmetry constraints that describe the staggered
spin accumulation responses, and disclose their fieldlike and dampinglike characters. This unravels a hidden
spin accumulation mode in AFM
semiconductors. Furthermore, we simulate such an effect using a perturbative approach and suggest that electric gate field and Floquet light-dressing can effectively manipulate these responses.
Read the full abstract ▾
Materials Science
Charting the thermodynamic stability of hybrid perovskite alloys with machine learning
Jarno Laakso, Armi Tiihonen and Patrick Rinke
Alloy-based perovskite
semiconductor materials offer tunable properties and improved stability, but their complexity has impeded accurate modeling, hindering development of
solar cell devices. We present a machine-learning (ML) accelerated atomistic modeling approach for the phase stability of (Cs/FA)Pb(Br/I)3 and (Cs/FA)Sn(Br/I)3 perovskites (where FA is formamidinium), that explicitly accounts for finite-temperature
entropy effects. To make such quaternary
alloy calculations tractable, we adopt a two-level strategy, combining 1) graph neural network interatomic potentials trained on density functional theory data for efficient structure relaxations with 2) direct energy predictions from unrelaxed structures to further accelerate the process. Our strategy enables computations of free energy landscapes across compositions and phases, capturing
alloy disorder and molecular orientations of FA. Our results reveal narrower regions of stable compositions for the Sn-based system compared to its Pb-based counterpart, limiting compositional engineering strategies for realizing devices that are robust in long term. High I contents result in maximum stability and no stabilization is observed near the center of the composition space. Our results guide the design of stable perovskite-based devices in experiments and demonstrate a workflow that is generalizable to other complex
alloy modeling tasks.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.supr-con
Stability Analysis of Superconductivity in $\textit{P6/mmm}$-LaSc$_2$H$_{24}$ and its Experimental Reproducibility from La-Sc Alloys
Dmitrii V. Semenok, Ivan A. Troyan, Zhongyan Wu et al. (+4 more)
In this work, we analyze the feasibility of room-temperature superconductivity in the lanthanum-scandium hydride $\textit{P6/mmm}$-LaSc$_2$H$_{24}$. We demonstrate that the electron-
phonon coupling calculations performed using the ${\sigma}$-broadening of the double ${\delta}$-function at the
Fermi surface lead to a very strong dependence of $\textit{T$_c$}({\sigma})$ on the arbitrary ${\sigma}$, whereas the tetrahedral method for the electron-
phonon interaction is free from this drawback and leads to $\textit{T$_c$}$ > 300 K at 300 GPa in agreement with previous predictions. By analyzing the stability of the metallic state of LaSc$_2$H$_{24}$ at 250-300 GPa, we show that this compound is at the edge of the stability region (${\xi}$ = 0.54), similar to $\textit{fcc}$ LaH$_{10}$ at 140-150 GPa. Seven experimental attempts to synthesize LaSc$_2$H$_{24}$ at 250-280 GPa starting from the (La,Sc$_2$)
alloy are unsuccessful and indicate the absence of even traces of superconductivity at 245-300 K in all the resulting La-Sc-H hydrides. The method for preparing the precursor by simultaneous deposition of La and Sc metals may be a key factor for the successful synthesis of LaSc$_2$H$_{24}$.
Read the full abstract ▾
All authors Dmitrii V. Semenok, Ivan A. Troyan, Zhongyan Wu, Di Zhou, Emil A. Yuzbashyan, Boris L. Altshuler, Viktor V. Struzhkin
Materials Science
Prototype-Guided Latent Alignment for Data-Efficient Fine-Tuning of Molecular Foundation Models
Rushikesh Pawar, Harshit Rawat, Ayush Kumar et al. (+1 more)
Machine learning interatomic potentials (MLIPs) have transformed materials discovery by leveraging graph neural networks (GNNs) to predict material properties with near density functional theory (DFT) accuracy. While large-scale pretrained foundation models offer transferable baseline representations, they frequently struggle to generalise to out-of-distribution (OOD) target systems – a common challenge in modelling complex or chemically diverse materials. Fine-tuning is the standard remedy, but the high cost of generating DFT-labelled configurations confines adaptation to data-scarce regimes, where over-parameterised GNNs amplify overfitting and degrade target-domain performance. To address this, we propose a prototype-based
alignment approach for data-efficient fine-tuning of MLIPs. Our method identifies local structural similarities between the source and target domains by grouping atoms with analogous chemical environments based on their latent representations. Each target-domain atom's energy contribution is aligned to its source-domain prototype, introducing an inductive bias that anchors fine-tuned representations to the pretrained structure, encouraging effective reuse of learned interactions and improving generalisation without restrictive assumptions on the target chemistry. We evaluate our method on the rMD17
benchmark using equivariant MACE and invariant SchNet across varying data budgets, and extend evaluation to the MACE-OFF foundation models on the SPICE
dataset. Our approach consistently improves predictive accuracy in the low-data regime, reducing energy MAE by up to 18% over standard fine-tuning baselines.
Read the full abstract ▾
All authors Rushikesh Pawar, Harshit Rawat, Ayush Kumar, Phani Motamarri
Materials Science · Cross-listed from cond-mat.soft
Synergistic approach to probing the dynamics and mechanics of patchy soft matter
Md Mozakker H. Shojib, Asier C. Monasterio, Emanuele Locatelli et al. (+3 more)
Tailoring microscopic details to tune bulk rheology is a key paradigm in soft matter physics, yet the vast parameter space associated with constituent interactions precludes a fully systematic approach. To address this, we have designed a synergistic strategy to explore the parameter space that comprises simulations, experimental rheology, and machine learning. As a case study, we choose DNA-based self-assembled fluids whose viscoelastic response can be fine-tuned by manipulating the base sequencing of the constituent nucleic acid nanostars. We use coarse-grained simulations, benchmarked against experimental data, to obtain the rheology of the DNA fluids, which feeds forward to a framework of Gaussian Process Regression and active learning. The latter is then used to explore the rheological design space with high predictive precision. The pipeline is designed to be deployed iteratively for the rational design and accelerated discovery of generic soft matter suspensions.
Read the full abstract ▾
All authors Md Mozakker H. Shojib, Asier C. Monasterio, Emanuele Locatelli, Pascal Friederich, Christopher Ness, Iliya D. Stoev
Materials Science
Carrier Localization in Pnictogen-Based Chalcohalides from Defect-Bound Hot Polarons
Xiaoyu Guo, Junzhi Ye, Cibrán Lopez Alvarez et al. (+19 more)
Pnictogen-based
solar absorbers have gained prominence as promising nontoxic and stable alternatives to lead-halide perovskites (LHPs), but are severely limited by carrier localization, preventing their performance from approaching those of LHPs. Recent efforts have uncovered routes to overcome carrier localization, but these early efforts only considered intrinsic factors. Herein, we push beyond these limited early efforts, examining the role of defects, not only on cold carriers but also hot carriers. Focusing on the structurally one-dimensional pnictogen chalcohalide BiSBr, we find that whilst this material intrinsically does not exhibit carrier localization, vacancies introduced during synthesis or post-treatment lead to pronounced extrinsic self-trapping via the formation of defect-bound hot polarons-excited charge-carriers strongly coupled to local defect-induced vibrational modes. These above-gap defect states divert hot carriers from cooling to the band edge, thus depleting the mobile carrier population. Our findings establish the key role of defect-bound hot polarons in mediating extrinsic localization and offer new mechanistic insights into the interplay between defects,
lattice coupling, and excited-state charge-carrier transport, which are critical to designing efficient perovskite-inspired
solar absorbers.
Read the full abstract ▾
All authors Xiaoyu Guo, Junzhi Ye, Cibrán Lopez Alvarez, Maciej Oskar Liedke, Maik Butterling, Mutibah Alanazi, Yi-Teng Huang, Jiajie Wu, Zhilong Zhang, Lars Van Turnhout, Yorrick Boeije, Bofeng Xue, Qingyu Wang, Hugh Lohan, Seán R. Kavanagh, Andreas Wagner, Eric Hirschmann, Robert A. Taylor, Akshay Rao, Edgardo Saucedo, Claudio Cazorla, Robert L. Z. Hoye
Materials Science · Cross-listed from cond-mat.str-el
Field-induced multipolar character in the dipolar ground state of the honeycomb rare-earth chalcohalide NdOF
Tiantian Liu, Yanzhen Cai, Mingtai Xie et al. (+6 more)
Field-tunable reconstruction of crystalline electric field (CEF) doublets offers a promising avenue for inducing multipolar character, while its observation in real materials has been little explored so far. Here we establish the honeycomb rare-earth chalcohalide NdOF as such a platform. Raman spectroscopy identifies four CEF excitations at 1.7, 15.6, 19.2, and 80.9~meV, and a Zeeman–CEF analysis reproduces their nonlinear field splitting into seven branches. Magnetization and susceptibility over 0.1–9~T are well described by a CEF model for the total angular momentum $J = 9/2$
manifold, confirming the robustness of the extracted CEF scheme. These results demonstrate a field-driven continuous
evolution of the ground-state doublet from dipolar to dipolar-multipolar character, with pressure providing a complementary tuning knob, establishing NdOF as a model system for exploring the controlled induction of multipolar components in rare-earth magnets.
Read the full abstract ▾
All authors Tiantian Liu, Yanzhen Cai, Mingtai Xie, Helin Mei, Anmin Zhang, Feng Jin, Jianting Ji, Zheng Zhang, Qingming Zhang
Materials Science
Topological spin-texture transitions in van der Waals magnets revealed by X-ray Fourier transform holography
Sourav Chowdhury, Soumyaranjan Dash, Michael Schneider et al. (+14 more)
Nontrivial topological
spin-textures, such as skyrmions, merons, bimerons, and skyrmioniums, are envisioned as robust building blocks for future
memory and logic devices. Controllable transformations between these states require a
quantum-mechanical description of electronic degrees of freedom and atomic-scale insight beyond existing phenomenological models. Here, we report an atomic-scale investigation of topological phase transitions and their protection in the two-dimensional van der Waals ferromagnet Fe$_3$GeTe$_2$ (FGT) using a combined experimental-theoretical approach. Synchrotron-based
Fourier transform holography directly images labyrinth domains, isolated skyrmions, mixed labyrinth-skyrmion phases, and skyrmion bags with high spatial resolution. We compare these observations to simulations based on an electronic
lattice Hamiltonian that captures both
metallicity and relativistic
spin-orbit coupling in FGT. By systematically exploring a broad range of temperatures and
magnetic fields, we map the mechanisms governing topological transitions and their stability. This sequential-integrated experimental-theoretical framework advances understanding of
spin-texture interactions and enables precise control of external tuning parameters. Our results establish a platform for creating, stabilizing, and manipulating topological states, paving the way for engineered
spin-texture transitions in next-generation spintronic technologies.
Read the full abstract ▾
All authors Sourav Chowdhury, Soumyaranjan Dash, Michael Schneider, Christopher Klose, Chithra H. Sharma, Lisa-Marie Kern, Tim A. Butcher, Josefin Fuchs, Santanu Pakhira, Samik DuttaGupta, Takashi Taniguchi, Kenji Watanabe, Sujit Das, Sanjeev Kumar, Bastian Pfau, Amir-Abbas Haghighirad, Moritz Hoesch
Materials Science · Cross-listed from cond-mat.mes-hall
Macroscopic evidence of spatial modulation of conductivity in a microtextured ferromagnetic film
C.P. Quinteros, L. Avilés-Félix, D. Goijman et al. (+5 more)
A 75 nm-thick Fe0.5Pt0.5 film is a
ferromagnetic metal showing striped
magnetic domains in remanence at room temperature. The magnetoresistance is characterized by varying the external temperature and the in-plane
magnetic field intensity, thereby affecting its
magnetic structure. Qualitatively, the resistivity is well described by using the generalized Ohm's law. High-field magnetotransport properties are successfully explained by considering the competition between the expected metallic behavior and the electron-
magnon interaction. In the low-field condition, we size the contribution of the
magnetic texture to the macroscopic magnetotransport response by introducing a new quantity. Consistent with the microscopic modulation of the lateral conduction, low-field measurements reveal inhomogeneities attributed to the spatial distribution of
ferromagnetic domains and domain walls. By carefully analyzing the macroscopic response near the coercive field, the additional contribution to the resistivity is attributed to the domain walls themselves. In fact, this term could surpass the anisotropic term at low temperatures. In summary, this study demonstrates that spatial
magnetic inhomogeneities are not only macroscopically measurable but also comparable in magnitude to other regularly considered terms, mainly at low temperatures.
Read the full abstract ▾
All authors C.P. Quinteros, L. Avilés-Félix, D. Goijman, L. Saba, D. Pérez Morelo, L. Granja, M. Granada, J. Milano
Materials Science
Optical Cooling of Nuclear Spins in a CdTe/CdZnTe Quantum Well: The Impact of Kinetic Local Fields on Cooling Efficiency
V. M. Litvyak, P. S. Bazhin, R. André et al. (+1 more)
The efficiency of optical cooling of
nuclear spins in a CdTe/CdZnTe
quantum well is investigated as a function of an external
magnetic field. Our results confirm that there is indeed an optimal external
magnetic field for optical cooling. We associate it with the kinetic local field $B_{KL}$ defined by the heating rate of the
spin-
spin reservoir due to the fluctuations of the hyperfine interaction. We also propose an experimental technique for measuring $B_{KL}$. For our sample we find that $B_{KL}=1.0\pm0.4$ G and it is independent of the electron polarization and pump power. The measured values of the kinetic local fields are in good agreement with a theoretical calculation $B_{KL} = 0.7$ G, taking into account indirect
spin-
spin interactions of Cd and Te
nuclear spins and their considerably different hyperfine constants. The hyperfine constants of the
magnetic isotopes of Cd and Te in CdTe are estimated.
Read the full abstract ▾
All authors V. M. Litvyak, P. S. Bazhin, R. André, K. V. Kavokin
Materials Science
Accelerated Discovery of Nitrogen-Coordinated Dual-Atom Hydrogen Evolution Reaction Electrocatalysts via Machine Learning Potentials
Yanmei Zang, Hyun Gyu Park, Gi Beom Sim et al. (+7 more)
The hydrogen
evolution reaction (HER) is central to sustainable hydrogen production, and nitrogen coordinated dual atom catalysts (DACs) offer a promising route to noble metal activity at low cost. Yet their vast compositional and coordination design space remains underexplored, as density functional theory (DFT) screening at scale is prohibitive. Here, we map the HER landscape of
graphene supported TM2@Nx-Gr DACs, screening 23 transition metals across 20 nitrogen coordination motifs using a machine learning potential (MLP) benchmarked against DFT. Intermediate coordination (2N to 4N) consistently yields near-optimal {\Delta}GH*, with Ti2@2Na, Mn2@2Na, Fe2@2Na, Cu2@2Na, Rh2@2Na, Zr2@2Na, Zr2@2Nb, Zr2@2Nc, Nb2@2Nc, Zr2@2Nd, Mn2@2Ne, Mn2@2Nf, Ti2@3Na, Au2@3Na, Fe2@3Na, Pd2@3Nb, Rh2@3Nc, Rh2@3Nd, Au2@3Nd, V2@4Na, Ti2@4Nb, Pd2@4Nb, Ti2@4Nc, Cr2@4Nd, Ni2@4Nd, Cu2@4Nd emerging as standout, synthesizable candidates, most exhibiting metallic or narrow gap (<0.25 eV) character. The MLP reaches near-DFT accuracy, with a mean absolute error of 80 meV for Gibbs binding free energies at orders of magnitude lower computational cost, establishing MLP driven screening as a practical engine for next-generation catalyst discovery.
Read the full abstract ▾
All authors Yanmei Zang, Hyun Gyu Park, Gi Beom Sim, Tae Hyeon Park, Ho Jin Lee, Xiaorong Zou, D. ChangMo Yang, Soohaeng Yoo Willow, Hye Jung Kim, Chang Woo Myung
Materials Science
Breaking Bipartite and Time Reversal Symmetries by Fusing Porphine Unit in-between two Zigzag-edge Graphene Nanoribbons
R. K. Rohit, Jisvin Sam and Sudipta Dutta
Hybrid structure of two zigzag-edge
graphene nanoribbons with a fused porphine ring in between, results in two distinct nearly degenerate ground states: a semiconducting
antiferromagnetic state and a conducting
ferromagnetic state with unequal and opposite
Fermi velocities of majority and minority
spins, the former having slightly higher stability. Such ground states result from the broken bipartite
symmetry induced by the porphine ring. The incorporation of different transition metal atoms in the porphine cavity reduces their energy difference but keeps their electronic properties mostly unchanged. The splitting of the $d$-orbitals in the distorted square-planar ligand field of porphine produces a high
spin ground state that breaks the global time reversal
symmetry ($\mathcal{T}$). The opposite
Fermi velocities of the majority and minority
spins in the
ferromagnetic ground state and lower sensitivity of the conducting majority
spin channel to the edge disorder, make this class of quasi-one-dimensional hybrid structures promising for dual
spin-filtering device applications.
Read the full abstract ▾
Materials Science · Cross-listed from cs.CV
Low-Magnification SEM May Suffice: Interpretable Deep Learning for Multi-Scale Fracture-Cause Classification in Zirconia-Toughened Alumina
Julian Schmid, Pawel Astankow, Tom Vater et al. (+3 more)
Reliable identification of fracture origins in alumina
matrix composite hip and knee implants is critical for quality assurance and patient safety, yet current fractographic workflows are time-consuming, partly subjective, and reliant on high-magnification scanning electron microscopy (SEM). We present an interpretable
vision-
transformer (ViT) workflow for automated classification of fracture causes in an alumina
matrix composite (BIOLOX delta, CeramTec GmbH) widely used in total joint replacements. A
dataset of 8,493 SEM images (50x-10,000x) was curated from five years of in-production burst and proof tests and annotated into three defect categories defined along the manufacturing chain: green body, hard machining, and material defects. Under severe class imbalance, the fine-tuned ViT reached an accuracy of 0.907 and a macro-F1 of 0.888 in stratified five-fold cross-validation, with a two-stage perceptual-hash/SSIM leakage audit confirming negligible specimen overlap. Notably, performance at low magnification (50x) was comparable to that at high magnification (1k-10kx), indicating that macro-scale features - mirror geometry and hackle line fields - already encode sufficient diagnostic signal. Grad-CAM attributions consistently localised on canonical fractographic cues (mirrors, hackles, pores, machining marks), aligning with established fractographic criteria. Together, these results position interpretable ViTs as a complementary tool for ceramic-implant quality assurance, enabling low-magnification pre-screening and reducing reliance on time-intensive high-magnification inspection.
Read the full abstract ▾
All authors Julian Schmid, Pawel Astankow, Tom Vater, Julius Beck, Robert Cichon, Danny Krautz
Materials Science
Spin-Orbit Coupling Effects on the Structural and Electronic Properties of Planar Pentagonal p-MS$_{2}$ (M = Si, Ge, and Pb)
Phuc-Dang Truong, Cao-Huu-Tai Nguyen, Nguyen-Bao-Tran Ngo et al. (+5 more)
Spin-orbit coupling (SOC) plays an important role in determining the structural and electronic properties of recently proposed two-dimensional planar pentagonal materials. In this work, density functional theory calculations are employed to investigate SOC effects in p-MS$_{2}$ systems (M = Si, Ge, and Pb). Our results indicate that the p-SiS$_{2}$ structure is likely unstable, except for p-GeS$_{2}$ and p-PbS$_{2}$. A detailed j-resolved (total angular momentum) orbital analysis reveals that SOC enhances electronic localization, leading to a slight structural contraction and a reconstruction of electronic states near the
Fermi level, this effect becoming stronger for heavier M atoms. While p-GeS$_{2}$ remains metallic, SOC drives a metal-
semiconductor transition in p-PbS$_{2}$ and opening a quasi-direct band gap of about 0.475 eV. In addition, the conduction band minimum state of p-PbS$_{2}$ exhibits pronounced anisotropy along the S-S bonds. These findings provide insight into SOC-driven structural and electronic reconstruction in planar pentagonal chalcogenides p-MS$_{2}$ and suggest that p-PbS$_{2}$ may be a promising candidate for gas-sensing applications.
Read the full abstract ▾
All authors Phuc-Dang Truong, Cao-Huu-Tai Nguyen, Nguyen-Bao-Tran Ngo, Khanh-Van Huynh, Jan Minar, Worawat Meevasana, Yen-Mi Tran, Trung-Phuc Vo
Materials Science
Transition metal (group V) doping induced spin and valley polarization in MoS$_2$ monolayer
Shivani Kumawat, Sunil Kumar and B. K. Mani
Doping in two-dimensional materials has emerged as an effective tool for modulating their electronic properties and thereby enabling their multifunctional applications. In this work, we present a first-principles study on induced effective
magnetic moment and
metallicity in MoS$_2$ monolayer by substitutional doping of group-5 transition metal (TM) elements – V, Nb and Ta. From our study, we observe that the V doping induces half-
metallicity, whereas metallic characteristics are observed in the case of Nb and Ta doping. Moreover, V and Ta-doped MoS$_2$ monolayers are observed to show total induced
magnetic moments of 0.922 and 0.624 $\mu_{\rm B}$, respectively. Importantly, the combined effects of strong
spin-orbit coupling (SOC), broken inversion
symmetry, and structural asymmetry is observed to lead to a permanent valley polarization in the V- and Ta-MoS$_2$ systems. In particular, we observed a valley polarization of 121 and 21 meVs for V and Ta-doped MoS$_2$, respectively. Furthermore, an enhanced piezoelectric coefficient for the doped systems is observed compared to pristine MoS$_2$. Notably, the simultaneous presence of half-
metallicity, substantial valley polarization, and enhanced piezoelectricity in V-doped MoS$_2$ establishes this system as a promising multifunctional platform for next-generation spintronic, valleytronic, and piezoelectric nanodevices. Overall, our findings provide fundamental insights into engineering coupled
spin-valley-mechanical degrees of freedom in two-dimensional materials for advanced
quantum and nanoelectronic applications.
Read the full abstract ▾
Materials Science
Finite-temperature micromagnetic model bridging atomic- and macro-scale magnetism
R. Kiefe and J. S. Amaral
A multi-scale finite-temperature micromagnetic model is presented, based on the Landau-Lifshitz equation and the Bernoulli differential equation. This model accurately reproduces classic Maxwell magnetostatics of paramagnets for high temperatures and accurately reproduces standard micromagnetics described by the conventional Landau-Lifshitz model in ferromagnets. The Landau-Lifshitz-Bernoulli (LLBe) model can, by design, directly couple atomic-scale simulations with micromagnetics and output consistent predictions of bulk
magnetic properties at finite temperatures, from below to above the material's Curie temperature. The LLBe model is validated against established solvers: MUMAX3 for zero-temperature micromagnetics, and FEMCE for high-temperature classic magnetostatics. We present an application of the LLBe model by simulating Heat-Assisted
magnetic recording on a thin
magnetic track with local heating, demonstrating the multi-scale finite-temperature capabilities of the LLBe.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.mes-hall
Disentangling Spin Pumping and Two-Magnon Scattering Contributions to Gilbert Damping in YIG/V Bilayers
S. Elkady, A. Tlais, H. Reslan et al. (+2 more)
In this work, we investigate the
magnetic damping and
spin pumping response of YIG-based
bilayers incorporating vanadium (V) as the normal metal layer via broadband
ferromagnetic resonance (FMR) measurements as a function of YIG thickness. We show that the apparent enhancement of the Gilbert damping in YIG/V
bilayers cannot be solely attributed to
spin pumping. Instead, two-
magnon scattering (TMS) plays a dominant role in governing the thickness dependence of the damping in the nanometer regime. By applying a thickness-dependent damping model that accounts for both
spin pumping and two-
magnon scattering contributions, we successfully disentangle the different relaxation contributions. Our analysis reveals that neglecting two-
magnon scattering leads to an overestimation of the
spin-pumping contribution and consequently to unphysically large values of the effective
spin-mixing conductance. After isolating the intrinsic
spin pumping contribution, we extract a thickness-independent effective
spin-mixing conductance of $g^{\uparrow\downarrow}_{\mathrm{eff}} = 1.33 \times 10^{18}~\mathrm{m^{-2}}$. These findings provide a more accurate framework for quantifying
spin transport parameters in FM/HM systems and emphasize the necessity of accounting for extrinsic damping mechanisms when interpreting
spin pumping and inverse
spin Hall effect experiments.
Read the full abstract ▾
All authors S. Elkady, A. Tlais, H. Reslan, S. Isber, M. Haidar
Materials Science · Cross-listed from cond-mat.mes-hall
Revealing quantum metric multipoles in magnetic topological insulator MnBi2Te4
Lars Sjöström, Prasanna Rout, Shahid Sattar et al. (+9 more)
Nonlinear electronic transport has emerged as a powerful probe of the
quantum geometry in topological
quantum materials, where the band
topology and broken
symmetries facilitate power law current voltage responses beyond Ohms law. While nonlinear transport of the second and third orders has been studied in several
quantum materials, higher-order transport has so far mainly remained experimentally inaccessible, leaving more detailed features of the
quantum geometry unexplored. Here, we observe higher order nonlinear electronic transport up to the seventh harmonic order in multilayer
magnetic topological
insulator MnBi2Te4. We find an even-odd behavior where the odd order nonlinear transport components dominate while the even-order ones are suppressed. Temperature and
magnetic field dependent measurements show a strong correlation between the nonlinear transport and the
magnetic phases of MnBi2Te4. Through scaling analysis and theoretical calculations,
quantum metric multipoles and nonlinear Drude conductivities are identified as the microscopic origins of the nonlinear transport.
Read the full abstract ▾
All authors Lars Sjöström, Prasanna Rout, Shahid Sattar, Alexander Tyner, Maurice E. Bal, Ankit Khola, Elias Rasmussen, Khadiza Ali, Arumugum Thamizhavel, Uli Zeitler, Carlo M. Canali, Saroj P. Dash
Materials Science
Alternative origins of polarity in compressively strained SrTiO3-RENiO3 capacitors
Evgenios Stylianidis, Panagiotis Koutsogiannis, Alexander Lione et al. (+8 more)
Since its original prediction 25 years ago, room-temperature out-of-plane ferroelectricity in compressively strained SrTiO3 remains an ongoing pursuit. In this work, we investigate the structural, electrical and electromechanical properties of highly strained epitaxial SrTiO3 capacitors with rare earth nickelate electrodes. The SrTiO3 layers experience compressive strains up to -3% and exhibit pronounced tetragonality, comparable to that of bulk PbTiO3. Variable-temperature electrical measurements and room-temperature piezoresponse force microscopy reveal butterfly-shaped capacitance-voltage hysteresis and domain-like electromechanical response typical of ferroelectric materials. However, the overall behavior is inconsistent with a stable ferroelectric state. We therefore propose an alternative mechanism for the observed polarity in our samples based on spatially inhomogeneous internal fields. Our first-principles calculations show that such fields may arise from charge discontinuities between the formally charged NdNiO3 layers and charge-neutral SrTiO3 layers.
Read the full abstract ▾
All authors Evgenios Stylianidis, Panagiotis Koutsogiannis, Alexander Lione, Felix Risch, Laura Hechler, Igor Stolichnov, Jorge Íñiguez-González, José A. Pardo, Nicholas C. Bristowe, César Magén, Pavlo Zubko
Materials Science
Synthesizability, hardness, and stacking order in multicomponent transition metal carbides from machine-learned potentials
Xin Liu and Anirudh Raju Natarajan
Multicomponent transition metal carbides are promising for extreme-environment applications, but identifying compositions that are both synthesizable and hard remains challenging. We fine-tune the MACE machine-learned interatomic potential on approximately 28,000 density functional theory calculations spanning the composition space of groups 4-6 transition metals and carbon to predict the thermodynamic stability and elastic properties of multicomponent carbides. The fine-tuned model achieves formation energy errors of ~ 10 meV/atom for thermodynamically relevant structures with only 20% of the training data. We screen over 1500 equiatomic compositions across rocksalt, hexagonal, and hcp prototypes, combining free energy models with elasticity-based hardness surrogates. Synthesizability predictions at 1500{\deg}C agree well with experimental reports for both single-phase and multiphase carbides. The group number of the constituent metals governs both stability and hardness. Free energy contributions from short-range order are small, typically a few meV/atom, indicating that a perfectly disordered solid solution provides a reasonable approximation for high-throughput screening. For compositions mixing group 4/5 and group 6 metals, we identify a new family of stacking-ordered phases with formation energies well below those of disordered rocksalt or hexagonal structures. DFT calculations corroborate these predictions and suggest that stacking-ordered phases should be experimentally accessible in multicomponent carbides. This study provides a framework for screening synthesizable multicomponent materials with target properties, identifies promising carbide compositions across the full nine-component space, and reveals a new class of stacking-ordered carbides accessible only in multicomponent compositions.
Read the full abstract ▾
Materials Science
Dynamic charges effect on infrared dielectric response of polar materials
Wei-Zhe Yuan, Yangyu Guo and Hong-Liang Yi
Predictive modeling of the infrared dielectric function in polar materials is crucial for thermal management and infrared devices design. While the Green-Kubo molecular dynamics (MD) framework provides a nonperturbative route to compute dielectric responses from dipole fluctuations, yet it commonly relies on the fixed-charge approximation that neglects dynamic charge redistribution during atomic motion. Here, we employ a machine-learning neuroevolution potential with dynamic charges (qNEP) combined with Green-Kubo MD to investigate the dynamic charge effect on the infrared dielectric response of rutile TiO$_2$, a material with large Born effective charges (BEC). Our results show that dynamic charge effects become increasingly important at elevated temperatures and are essential for accurately predicting longitudinal optical
phonon features and infrared reflectance. This work establishes that accurate prediction of infrared optical properties in polar materials under thermal excitation requires explicit treatment of dynamic charge
evolution.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Source-driven torsional optical activity in geometrically chiral media
Edilberto O. Silva
We develop an effective field-theoretical model for source-driven electromagnetic waves in a geometrically
chiral optical medium described by a uniform axial torsion. Starting from the gauge-invariant electromagnetic field strength, we introduce a Chern–Simons-type coupling between the vector potential and the medium's axial contortion, thereby obtaining an inhomogeneous Maxwell system with prescribed external sources. For transverse cylindrical source profiles, we derive the coupled radial equations and solve them analytically for a circulating cylindrical-shell current. In the circular basis, the homogeneous problem diagonalizes, yielding torsion-split radial wavenumbers that give rise to longitudinal circular birefringence under guided-mode boundary conditions. In the weak-torsion regime, this birefringence produces a polarization rotation proportional to the propagation length and an oscillatory conversion between orthogonal linear polarizations. The source fixes the jump conditions and the relative excitation of the circular eigenmodes, thereby yielding measurable modal power and Poynting-flow signatures. A two-port scattering analysis shows that the apparent direction dependence remains Lorentz reciprocal, placing the effect in the class of reciprocal
geometric optical activity rather than Faraday isolation.
Read the full abstract ▾
Materials Science
Topological Lifshitz transition-induced bipolarity of anomalous Nernst effect in kagome magnet YCo3
Sheng Xu, Yue-Yang Wu, Hao-Ran Bai et al. (+10 more)
The kagome
lattice, renowned for hosting topological band structures and rich
magnetic behaviors, offers an exceptional setting to investigate unconventional transport in
magnetic topological systems. Controlling the polarity of the anomalous Nernst effect (ANE) is crucial for designing flexible thermoelectric devices, such as thermopiles, where the ability to switch the thermoelectric voltage sign can dramatically enhance energy conversion efficiency and output. Here, we demonstrate such a bipolar ANE in the kagome magnet YCo3, driven by a temperature-induced topological Lifshitz transition. With a Curie temperature TC~225 K, sizable anomalous
Hall and Nernst effects emerge below TC. Supported by the first-principles calculations, the AHE and ANE are suggested to be dominated by the intrinsic mechanism. Furthermore, the intrinsic anomalous
Hall conductivity exhibits a piecewise-linear dependence on magnetization, with an abrupt slope change near 100 K, consistent with the Karplus-Luttinger mechanism. Concurrently, the anomalous Nernst coefficient SAyx reverses its sign around the same temperature, realizing the crucial bipolarity. These anomalies could be interpreted as a topological Lifshitz transition, enabled by the
evolution of Co moments that could shift the
Fermi level relative to Weyl nodes. Our work reveals YCo3 as a prototypical kagome magnet where temperature and magnetism directly govern both Weyl node
topology and the bipolar ANE, opening a pathway to magnetically control thermoelectric output in topological
quantum materials.
Read the full abstract ▾
All authors Sheng Xu, Yue-Yang Wu, Hao-Ran Bai, Zheng Li, Shu-Xiang Li, Jun-Jian Mi, Tian-Hao Li, Ze-Wei Wang, Ze-Kai Dong, Jiang Ma, Xiao-Bo Wu, Qian Tao, Zhu-An Xu