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Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Monday 13 April

Materials Science

Revealing Dislocation Interactions Controlling Mechanical Properties of Metals

Felix Frankus, Sina Borgi, Albert Zelenika et al. (+4 more)

During plastic deformation, metals change shape while continuously becoming stronger. The microscopic origin of these processes lies in the proliferation and movement of line defects, dislocations, and the subsequent self-organisation and pinning of dislocations on lattice imperfections, including other dislocations. The nature of these multiscale processes has remained elusive because in situ observations have not been feasible. We present 3D movies of how dislocations pile up near an obstacle, deeply within a mm-sized pure Al sample and during tensile deformation. Cross-slip is found to provide a mechanism for the dislocations to escape the pile-up, leading to pronounced intermittent behaviour. Such data support a new generation of dislocation dynamics and micro-mechanics modelling.
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All authors Felix Frankus, Sina Borgi, Albert Zelenika, Basit Ali, Raquel Rodriguez-Lamas, Henning Friis Poulsen, Grethe Winther

Materials Science

Ru Alloying in Ni/Al Reactive Multilayers: Experimental Observations and Molecular Dynamics Simulations

Nensi Toncich, Ankit Yadav, Jan Fikar et al. (+1 more)

Reactive multilayer thin films, a class of energetic materials, are increasingly recognized for their potential in joining applications, utilizing the chemical energy released as heat during exothermic reactions. These materials hold also promise for additional diverse technological applications, which require precise control over heat release rates and reaction propagation velocities. The microstructural properties of reactive multilayers play a critical role in determining their chemical reaction behavior. Among these, Ni/Al reactive multilayers have been extensively studied and used due to their favorable characteristics. In this study, we explore the incorporation of ruthenium (Ru) as a co-alloying element with nickel (Ni) in the Ni/Al system to investigate its impact on the materials properties, with a particular focus on reaction velocity and temperature. Ru enhances the reaction rates, but also causes a composition dependent phase transition in the as-deposited state from fcc to hcp. Additionally, molecular dynamics simulations are employed to examine the effects of Ru co-alloying with Ni, providing deeper insights into the underlying mechanisms. This work aims to advance the understanding of Ru's role in influencing the performance of Al/Ni-based reactive multilayers for advanced applications.
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All authors Nensi Toncich, Ankit Yadav, Jan Fikar, Ralph Spolenak

Materials Science · Cross-listed from cond-mat.mes-hall

Strain-Induced Curvature in Monolayer Graphene: Effects on Electronic Structure, Phonon Dynamics, and Lattice Thermal Conductivity

M. C. Santos, E. Lora da Silva, D. S. Baptista et al. (+6 more)

We present a comprehensive set of calculations to investigate the effect of strain-induced x-y topological perturbation in the monolayer graphene sheet. We show that the induced curvature with the defined strain constraint, energetically stabilizes the systems. The electronic properties are modified when the amplitude of the curvature of the sheet increases, which induces Van Hove singularities of the electronic Density of States to approach the Fermi energy. The highly curved system exhibits coexisting flat and linear dispersions close to the Fermi level, which is a promising feature for thermoelectric applications. We also demonstrate, through the phonon dispersion curves, that respective systems are dynamically stable within the studied range of strains/curvatures. Moreover, the flexural acoustic mode transitions from quadratic to linear dispersion under strain, mimicking the 3D behavior and enhancing phonon scattering. The increase of phonon scattering will therefore decrease the value of the lattice thermal conductivity, $\kappa_L$. Such results allows us to conclude that it is possible to tune $\kappa_L$ by applying x-y strain to the monolayer sheet, and inducing different topological curvatures.
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All authors M. C. Santos, E. Lora da Silva, D. S. Baptista, T. Santos, M. Molinari, F. J. Manjón, Yin Cui, Xidong Lin, Tao Yang

Materials Science · Cross-listed from cond-mat.mes-hall

Ultrafast ghost Hall states in a 2d altermagnet

Ruikai Wu, Deepika Gill, Sangeeta Sharma et al. (+1 more)

Two-dimensional materials that exhibit optically active spin and valley degrees of freedom represent one of the most fascinating – and potentially most technologically useful – platforms for the ultrafast interaction of light and matter. Here we show, via the example of Cr$_2$SO, that two dimensional altermagnets host valley states controllable by femtosecond laser light: linearly polarized light pulses excite charge at one of two inequivalent valleys, with which valley charge is excited at determined by the polarization vector direction. This underpins a rich spin and valley physics including: (i) valleytronics $-$ the generation of nearly 100$\%$ spin polarized valley currents, as well as (ii) a "ghost Hall" effect $-$ the ultrafast creation of states in which spin and charge currents are orthogonal without invoking Hall physics. Our findings establish 2d altermagents as a platform providing a new route for the control of spin- and charge currents at ultrafast times.
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All authors Ruikai Wu, Deepika Gill, Sangeeta Sharma, Sam Shallcross

Materials Science · Cross-listed from physics.app-ph

ALD W-Doped SnO$_2$ TFTs for Indium-Free BEOL Electronics

Mansi Anil Patil, Devarshi Dhoble, Shivaram Kubakaddi et al. (+4 more)

This work reports back-end-of-line (BEOL) compatible, thin-film transistors (TFTs) with sub-10 nm tungsten-doped tin oxide (TWO) channels deposited by atomic layer deposition (ALD) at 150 $^\circ$C. TFTs with undoped SnO$_{\mathrm{x}}$, undoped WO$_{\mathrm{x}}$, and W-doped SnO$_{\mathrm{x}}$ channels with W concentrations of 5% and 10% were investigated. TFT with 10% W doping exhibited the best electrostatic control and overall device performance. Post-fabrication O$_{\mathrm{2}}$ annealing at 300 $^\circ$C for 5 minutes significantly enhanced device characteristics, reducing the subthreshold swing (SS) by nearly 2$\times$, increasing the I$_{\mathrm{on}}$/I$_{\mathrm{off}}$ ratio from $10^7$ to $10^9$, decreasing hysteresis by nearly 3$\times$ and positive bias stress-induced threshold shift by over 2$\times$ to a low value of 93 mV at a stress field of 4 MV/cm. Kinetic Monte Carlo simulations using Ginestra$^{\mathrm{TM}}$ support the experimental observations and attribute the bias instability to charge trapping in the gate dielectric and at the interface. This work demonstrates low-temperature ALD-grown TWO TFTs as a promising indium-free platform for BEOL and monolithic 3D integration.
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All authors Mansi Anil Patil, Devarshi Dhoble, Shivaram Kubakaddi, Mamta Raturi, Marco A Villena, Gaurav Thareja, Saurabh Lodha

Materials Science

A new helical InSeI polymorph: crystal structure and polarized Raman spectroscopy study

Lucía Olano-Vegas, Davide Spirito, Evgeny Modin et al. (+7 more)

Tetragonal InSeI is an interesting low-dimensional metal chalcohalide due to its composition and anisotropic crystal structure composed of helical chains, which give rise to optoelectronic properties with potential application in photodetectors, optical thermometers, and spintronic devices. However, experimental works lack on the study of its anisotropic or chiral behavior. Here we present the crystal structure of an unreported InSeI polymorph and study its lattice dynamics in bulk crystals and exfoliated nanowires by polarized Raman spectroscopy for two non-equivalent crystallographic planes. We determine the orientation of the helical chains and distinguish between crystallographic planes by linearly polarized measurements, evaluating the angle-dependent intensity of the modes, which allows assigning each mode to its representation. Circularly polarized Raman measurements do not reveal chiral phonons, despite the helical chains and anisotropic crystal structure. These results offer insight into the crystal structure of InSeI, which is fundamental for the fabrication of orientation-dependent optoelectronic and spintronic devices.
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All authors Lucía Olano-Vegas, Davide Spirito, Evgeny Modin, Pavlo Solokha, Sergio Marras, Marco Gobbi, Fèlix Casanova, Serena De Negri, Luis E. Hueso, Beatriz Martín-García

Materials Science

Surface correlation functions of dead-leaves models

Cedric J. Gommes

The pore-surface and surface-surface correlation functions are structural characteristics that play an important role in theoretical materials science and in small-angle scattering theory. Exact analytical expressions for the surface correlation functions are available only for very few models, and we here derive such expressions for the general class of dead-leaves models. Within these models, a two-phase pore/solid structure is created by sequentially and randomly filling space with pore-like or solid-like grains that overlap any pre-existing structure, in the same way as dead leaves fall on the ground. The obtained mathematical expressions are valid for any grain shape, in arbitrary dimension. The results are illustrated with monodispersed spherical grains,as well as with a dead-leaves realization of a Debye random medium. In the latter case, the size distribution of the grains is designed to produce a structure having exponential two-point correlation function. Compared to Debye random media obtained by numerical reconstruction, the dead-leaves structure has almost identical surface-surface correlation function, but distinctly different pore-surface correlation function. As a byproduct of our analysis, we also submit a general expression for the pore-surface and surface-surface correlation functions of the Boolean model, valid for arbitrary grains.
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Materials Science

Density Functional Theory Study of Lanthanide Monoxides under High Pressure: Pressure-Induced B1-B2 Transition

Sergio Ferrari and Daniel Errandonea

Using density functional theory, we study the influence of hydrostatic pressure on the crystal structure of lanthanide monoxides, focusing on the monoxides formed by the fifteen elements of the lanthanide series, from La to Lu. Calculations are performed using two methods for the ambient pressure B1 (NaCl type) structure, the general gradient approximation (GGA) and the local density approximation (LDA). Through a systematic comparison with existent experimental data, we find that the first method agrees better with the experiments. In addition, considering other cubic structures previously reported for lanthanide monoxides, as B2 (CsCl type) and B3 (ZnS type), we explore the possibility of the occurrence of pressure-induced phase transitions. Based on the better accuracy of GGA to describe the B1 phase at ambient conditions, we exclusively use GGA for the high pressure study. We find, for the fifteen studied compounds, that, at ambient pressure, the B1 structure is the one with the lowest enthalpy, being therefore the most thermodynamically stable structure. We also determine that, at elevated pressures, all the studied compounds undergo a structural phase transition to the B2 phase. We finally establish the relationship between pressure and volume of the unit cell, along with the associated isothermal equation of state, determining the bulk modulus.
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Materials Science

High-Pressure Structural Evolution of Na2ZrSi2O7 and Na2ZrSi2O7.H2O: Topology-Driven Compression Behaviors, Phase Stability, and Electronic Transitions

Peijie Zhang, Pablo Botella, Neha Bura et al. (+6 more)

Silicate frameworks exhibit diverse structural responses under extreme conditions, which are strongly influenced by hydration. Here, we present a comparative high-pressure synchrotron X-ray diffraction study of Na2ZrSi2O7 and its hydrated analogue Na2ZrSi2O7.H2O up to 30 GPa, combined with electronic structure calculations. At ambient conditions, both phases share the same primary building units (PBUs: [ZrO6] and [SiO4]) but differ in secondary building units (SBUs, M2T4 vs. M2T6). Under compression, Na2ZrSi2O7 undergoes a phase transition near 15 GPa, while the hydrated phase remains stable throughout the pressure range. The anhydrous compound exhibits a higher bulk modulus (B0 = 77.1 GPa) and less anisotropic compression compared with the hydrated phase (B0 = 66.3 GPa). Distinct deformation mechanisms are observed: the anhydrous framework accommodates pressure through [ZrO6] octahedral distortion, whereas the hydrated framework compresses via [Si2O7] group tilting. Electronic structure calculations indicate band gap widening with pressure in both phases; notably, Na2ZrSi2O7 shows a direct-to-indirect band gap transition, whereas the hydrated phase retains a direct gap. These results reveal how hydration-driven topological modifications at the secondary building unit scale dictate the pressure-induced structural evolution, phase stability, and electronic properties of zirconosilicate frameworks.
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All authors Peijie Zhang, Pablo Botella, Neha Bura, Xiao Dong, Catalin Popescu, Yellampalli Raghavendra, Rakesh Shukla, Srungarpu Nagabhusan Achary, Daniel Errandonea

Materials Science

Ladder-like Structural Architecture of Layered Magnetic $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs) Compounds by Self-flux Synthesis

Kai D. Röseler, Felix Eder and Fabian O. von Rohr

The discovery and control of intergrowth structures represent an important avenue for the targeted synthesis of new, more complex structure types. When including magnetic framework metal atoms, this enhanced complexity can transfer to rich magnetic ground states. Here, we show that the subtle adjustment of the composition of alkali-tellurium fluxes enables the synthesis of a new family of alkali chromium tellurides, $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs). Their ladder-like crystal structures integrate the two-dimensional character of delafossite-like $A$CrTe$_2$ with the tunnel motifs of hollandite-like $A_{x}$Cr$_5$Te$_8$ phases. This results in a previously unobserved unique hybrid framework. Direction-dependent magnetization measurements on oriented single crystals reveal distinct magnetic ground states: Rb$_{2.4}$Cr$_8$Te$_{14}$ is antiferromagnetic with $T_{\rm N}$ = 114.5 K, while Cs$_{2.4}$Cr$_8$Te$_{14}$ is ferrimagnetic with $T_{\rm C}$ = 125.0 K. This work underscores the simplicity and effectiveness of flux growth as a design strategy for discovering low-dimensional materials.
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Materials Science

Band Tail State Broadening in IGZO TFTs After pBTI-Induced Negative VT Shift Revealed via DC and 1/f Noise Measurements

R. Asanovski, P. Rinaudo, A. Chasin et al. (+9 more)

We investigate the origin of negative threshold voltage shifts in back-gated amorphous IGZO TFTs under positive bias and high temperature stress. Combined DC and 1/f noise measurements reveal that the stress does not generate new dielectric traps but instead broadens the IGZO conduction band tail states. A recovery experiment confirms that the associated threshold voltage, subthreshold swing, and noise degradation are reversible. Simulations using an in-house Poisson solver confirm the experimental observations that high-temperature stress increases hydrogen doping and the density of sub-gap states.
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All authors R. Asanovski, P. Rinaudo, A. Chasin, Y. Zhao, H.F.W. Dekkers, M. J. van Setten, D. Matsubayashi, N. Rassoul, A. Belmonte, G.S. Kar, B. Kaczer, J. Franco

Materials Science

GPU acceleration of plane-wave density functional theory calculations in Abinit

Ioanna-Maria Lygatsika, Marc Sarraute, Lucas Baguet et al. (+2 more)

We report on the GPU port of the Abinit high-performance simulation code for plane-wave DFT calculations. Large-scale electronic structure calculations require computing the electronic wave function by solving the Kohn-Sham equations discretized over a large number of plane waves. Porting such calculations to GPU nodes relies not only on extensive usage of vendor libraries from a development perspective, but also on algorithmic revisions of the iterative diagonalization procedure in the resolution of the Kohn-Sham equations to identify GPU-efficient mathematical operations (linear algebra, FFTs) applied to the wave function distributed in memory. The present contribution discusses the Abinit implementation on multi-GPU architectures, providing detailed performance results for heterogeneous CPU-GPU nodes versus CPU nodes. Particular attention is given to comparing two diagonalization algorithms—Locally Optimal Block Preconditioned Conjugate Gradient and Chebyshev polynomial filtering—in terms of GPU efficiency.
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All authors Ioanna-Maria Lygatsika, Marc Sarraute, Lucas Baguet, Pierre Kestener, Marc Torrent

Materials Science

Effect of Indium doping on structural and thermoelec-tric properties of SnTe

Diptasikha Das, A. Jana, S. Mahakal et al. (+4 more)

The solid state reaction method is employed to synthesize Sn1-xInxTe samples. Power Factors of synthesized samples are estimated from resistivity and thermopower data. Modifications in structural parameters, resistivity and thermopower owing to In doping in SnTe thermoelectric material are reported. In-depth structural analysis, employing Rietveld refinement of X-ray diffraction data, confirms the substitution of Sn by In. A minute amount of embedded phases in synthesized samples is revealed from the refinement of X-ray diffraction data. Williamson-Hall and modified Williamson-Hall methods are employed to estimate dislocation density and strain. The highest power factor and maximum host phases are simultaneously achieved for the Sn0.96In0.04Te sample amid the synthesized Sn1-xInxTe samples.
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All authors Diptasikha Das, A. Jana, S. Mahakal, Pallabi Sardar, J. Seal, Shamima Hussain, Kartick Malik

Materials Science · Cross-listed from cond-mat.supr-con

Microscopic mechanism for resonant light-enhanced pair correlations in K$_3$C$_{60}$

Juan I. Aranzadi, Joseph Tindall, Paul Fadler et al. (+1 more)

Recent experiments on K3C60 revealed a giant enhancement of the light-induced superconducting-like optical response for pump frequencies near 10 THz, with an efficiency roughly two orders of magnitude larger than for off resonant excitation. Here we show that a resonant enhancement of pair correlations arises naturally in a driven purely electronic model of K$_3$C$_{60}$ with ab initio parameters. The underlying mechanism is a symmetry constrained two-photon pathway: the first photon drives the system from the even-parity ground state to an intermediate odd-parity manifold, while the second photon induces a transition to an even-parity excited state with enhanced pair correlations. Larger-cluster calculations show that the corresponding resonance energy is strongly renormalized downward with system size and connectivity, reflecting the kinetic-energy gain of delocalized photo-excited doublon-holon configurations. A simplified single-orbital model reproduces this scaling trend and reaches a 14-site fcc cluster, where the resonant peak is pushed to 30 THz, with a trend compatible with a further reduction toward the experimental 10 THz scale in larger systems. Varying the Hubbard coupling strength, we find that the resonance is lowest and the pairing enhancement strongest near intermediate couplings, where doublon-holon excitations are both well defined and mobile. Our results establish a purely electronic mechanism for resonant light-enhanced pair correlations in K$_3$C$_{60}$ and support the interpretation of the experimental 10 THz resonance as optical access to a paired many-body excited state rather than improved metallicity. More broadly, they suggest that related resonant pathways may arise in other intermediate-coupling Hubbard materials.
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All authors Juan I. Aranzadi, Joseph Tindall, Paul Fadler, Michael A. Sentef

Materials Science

opt-DDAP: Optimisable density-derived atomic point charges via automatic differentiation

Mohith H. and Sudarshan Vijay

Interatomic potentials which accurately describe long-range electrostatics require atom-centred charges. One such method to determine these atom-centred charges from density functional theory (DFT) calculations is the density-derived atomic point (DDAP) charge method. DDAP fits atom-centred Gaussians to the ground-state DFT charge density and preserves the multipole moments that govern long-range electrostatics. While these charges accurately predict long-range behaviour, in practice, they are limited by their reliance on fixed, heuristic parameters and a constrained solver that becomes numerically unstable for complex or covalent systems. In this work, we present opt-DDAP, which solves this limitation by reformulating the algorithm as a differentiable computational graph. This reformulation allows for the optimisation of Gaussian basis parameters and the reciprocal-space cutoff using automatic differentiation. To ensure numerical robustness through this automatic differentiation process, we replace the conventional Lagrange-multiplier approach with a pseudo-inverse solution followed by charge renormalisation, maintaining stability even in the presence of ill-conditioned matrices. We validate the framework on NaCl vacancy supercells and on MoS$_2$, demonstrating faithful reconstruction of both absolute and difference charge densities. The optimised charges are intended to serve as inputs to effective electrostatic models in machine-learning and empirical interatomic potentials that incorporate long-range interactions.
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Materials Science

A first-principles study of bcc chromium beyond the generalized gradient approximation (GGA)

Alma Partos, Igor Di Marco and Shivalika Sharma

The study of magnetism in transition metals is a cornerstone in understanding complex electronic and magnetic interactions in condensed matter systems. Among transition metal elements, body-centered cubic (bcc) chromium stands out because of its spin-density wave (SDW) ground state, posing a long-standing challenge for density functional theory (DFT). Conventional functionals, such as the generalized-gradient approximation (GGA) and the local-density approximation (LDA), fail to predict this experimentally observed incommensurate SDW as the ground state. In this study, we present a comprehensive DFT analysis of bcc Cr employing GGA and a variety of meta-GGA functionals. We evaluated total energies, structural parameters, and magnetic properties across a wide range of SDW wave vectors. Our results show that all meta-GGA functionals overestimate the local magnetic moments and enhance the nodal magnetic frustration, destabilizing the SDW state relative to the commensurate antiferromagnetic (AF) configuration. Tao-Perdew-Staroverov-Scuseria (TPSS) yields results closest to those of the GGA, thus providing the most adequate description of bcc Cr among the meta-GGA functionals. These results emphasize the need for the further development of non-local or hybrid functionals tailored for complex magnetic systems.
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Materials Science

A Lightweight Universal Machine-Learning Interatomic Potential via Knowledge Distillation for Scalable Atomistic Simulations

Sangmin Oh, Jinmu You, Jaesun Kim et al. (+4 more)

We introduce a lightweight universal machine-learning interatomic potential (uMLIP), SevenNet-Nano, based on the graph neural network architecture SevenNet and enabled by a knowledge-distillation framework. The model inherits the broad generalization capability of a large multi-task foundation model, SevenNet-Omni, trained on diverse materials datasets across chemical, configurational, and computational spaces. By learning chemical representations from high-quality inference data generated by the teacher model within a unified computational framework, SevenNet-Nano achieves high accuracy and strong transferability despite its compact architecture. The model also accurately captures a wide range of interatomic interactions, enabling reliable simulations under both equilibrium and extreme conditions, including plasma etching of SiO$_2$. Comprehensive benchmarks on static and dynamical properties–such as Li-ion diffusion and liquid densities–demonstrate its broad applicability with minimal fine-tuning. Importantly, SevenNet-Nano significantly reduces computational cost, achieving over an order-of-magnitude speedup and enabling large-scale atomistic simulations involving thousands of atoms.
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All authors Sangmin Oh, Jinmu You, Jaesun Kim, Jiho Lee, Hyungmin An, Seungwu Han, Youngho Kang

Sunday 12 April

Materials Science

Wavelength-dependent photo-creep in halide perovskite single crystals

Ruitian Chen, Jincong Pang, Lizhong Lang et al. (+9 more)

Halide perovskites are promising optoelectronic materials, but their time-dependent permanent deformation under illumination (i.e., photo-creep) is poorly understood, limiting their mechanical stability. Here we report wavelength-dependent photo-creep phenomena in CsPbBr3 and FAPbBr3 single crystals, studied by constant-load nanoindentation under controlled light with various wavelengths. Compared with creep in dark, continuous green light (near-bandgap) suppresses creep by 19% in CsPbBr3 and 10% in FAPbBr3, whereas violet (far above-bandgap) light enhances creep by 16% in CsPbBr3 and 8% in FAPbBr3. In contrast, when light is onset during creep, blue light enhances creep most prominently, whereas green light exhibits minimal influence. Such photo-creep behavior in halide perovskites are distinct with photo-plasticity phenomenon in conventional semiconductors. By combining the photoluminescence and photocurrent measurements, we unveil that ion migration promotes dislocation climb and creep, while carrier trapping suppresses dislocation glide and related creep in halide perovskites. Such competition between carrier trapping and ion migration tuned by wavelength governs the photo-creep response. Our findings uncover a photomechanical effect in halide perovskites and highlight how coupled carrier and ion dynamics under illumination affect their device reliability.
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All authors Ruitian Chen, Jincong Pang, Lizhong Lang, Jiaze Wu, Mingyu Xie, Shuo Yang, Kaiqi Qiu, Tobin Filleter, Kai Huang, Guangda Niu, Jiang Tang, Yu Zou

Materials Science · Cross-listed from cond-mat.str-el

Vacancy-driven inverse Lieb geometry: A general route to $d$-wave altermagnetism in two dimensions

Geethanjali S, Katsunori Wakabayashi and Sasmita Mohakud

Vacancy-induced structural reconstruction provides a general microscopic route to $d$-wave altermagnetism in two-dimensional systems. As a concrete realization, reconstructed $\mathrm{V_2X_2}$ ($\mathrm{X}=\mathrm{S}, \mathrm{Se}$) monolayers form an inverse Lieb magnetic network in which two inequivalent edge vanadium sites, related by $C_4$ lattice rotational symmetry and carrying opposite exchange fields, yield zero net magnetization despite broken time-reversal ($\mathcal{T}$) and combined inversion–time-reversal ($\mathcal{PT}$) symmetries. Structural stability is confirmed by formation energies, phonon spectra, and $ab$ $ initio$ molecular dynamics simulations at room temperature. A minimal tight-binding model, incorporating anisotropic second-order hopping between the inequivalent magnetic sites mediated by a nonmagnetic corner site, produces spin splitting with a $(\cos k_x - \cos k_y)$ form factor in quantitative agreement with first-principles calculations. The resulting spin splitting is strongly anisotropic, maximized near the $X$ and $Y$ high-symmetry points and exhibiting a symmetry-enforced nodal degeneracy at $M$, consistent with a $d_{x^2-y^2}$ altermagnetic form factor confirmed by the fourfold Fermi surface pattern. These findings establish vacancy-driven reconstruction of an inverse Lieb magnetic network as a general design principle for two-dimensional $d$-wave altermagnets.
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Materials Science

Surface ferrimagnetic order in RuO2 film

Jiahua Lu, Huangzhaoxiang Chen, Zhe Zhang et al. (+11 more)

RuO2, widely proposed as a prototypical altermagnet, remains intensely debated with regard to its magnetic nature. Here, we demonstrate that RuO2 is non-magnetic in the bulk, but possesses a spontaneous surface ferrimagnetic order. Using spin- and angle-resolved photoemission spectroscopy, we directly detect a narrow surface state with identical spin polarizations at opposite momenta and at the Brillouin-zone center, incompatible with the spin texture of any altermagnetic order. First-principles calculations identify the non-magnetic bulk state and reveal that the detected magnetism is confined to the fully oxygen-terminated surface, where the charge transfer from Ru to O at surface triggers a ferrimagnetic alignment between adjacent Ru sublattices with antiparallel moments of +0.48 uB and -0.04 uB. Our findings provide a unified explanation reconciling debating reports on the magnetism of RuO2, establishing surface ferrimagnetism as the origin of the observed magnetic signals, and distinguishing it unambiguously from altermagnetism.
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All authors Jiahua Lu, Huangzhaoxiang Chen, Zhe Zhang, Xinyue Wang, Donghang Xie, Bo Liu, Liang He, Yao Li, Jun Du, Zhi Wang, Junwei Luo, Rong Zhang, Yongbing Xu, Xuezhong Ruan

Materials Science

On stress-assisted boundary migration during recrystallization

Yubin Zhang, Qiwei Shi and Guilin Wu

This study investigates the boundary migration mechanisms near the sample surface of recrystallizing grains in high-purity Al subjected to cryogenic rolling. Local strain and stress tensors were characterized during in situ annealing by combining high-resolution electron backscatter diffraction with microstructure-based digital image correlation strain analysis. The results reveal local residual strains on the order of $10^{-3}$ within the recrystallizing grain, with values several times higher in the adjacent deformed matrix. The residual stresses in recrystallizing grains are a passive response to those developed within the surrounding deformed grains; the latter being strongly influenced by the local geometry and characteristics of dislocation boundaries, as well as by constraints imposed by neighboring grains. No evidence of shear-coupled motion was observed during the recrystallization boundary migration, despite the presence of shear stress across the boundary. In contrast, detailed analysis of the principal strain components reveals a clear correlation between residual strain patterns and boundary migration directions. These findings indicate that recrystallization boundary migration is modulated by the anisotropy of the local internal stress state.
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Materials Science

Electrochemical stability and lithium insertion at the Li|Li3OCl solid electrolyte interface

Deobrat Singh, Li-Yun Tian, Moyses Araujo et al. (+1 more)

Solid-state lithium batteries have attracted considerable attention due to their potential to provide improved safety and higher energy density compared with conventional liquid electrolyte batteries. However, the stability of the interface between Li metal anodes and solid electrolytes remains a critical issue that strongly influences battery performance. In this work, first-principles density functional theory calculations are performed to investigate the interfacial properties of a solid-state battery system composed of Li metal anode and Li3OCl solid electrolyte. The structural stability, electronic structure, and electrochemical behavior of the Li|Li3OCl interface are systematically analyzed. Several interface orientations are constructed and compared in order to identify the most energetically favorable configuration. The electronic properties and interfacial charge redistribution are further examined to understand the nature of the interaction between Li metal and the Li3OCl electrolyte. Our results indicate that the Li|Li3OCl interface exhibits stable structural and electronic characteristics, with localized charge redistribution occurring near the interface region. The electrochemical stability against the insertion of an additional Li atom is also evaluated, showing that Li incorporation is energetically unfavorable in most layers of the electrolyte. These results suggest that the Li3OCl electrolyte maintains good electrochemical stability in contact with Li metal. The present study provides atomic-scale insight into the interfacial behavior of Li|Li3OCl and highlights the potential of Li3OCl as a promising solid electrolyte for solid-state lithium batteries.
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All authors Deobrat Singh, Li-Yun Tian, Moyses Araujo, Raquel Lizarraga

Materials Science

Two-Dimensional Spin-Antiferroelectric Altermagnets with Giant Spin Splitting: From Model to Material Realization

Zesen Fu, Aolin Li, Wenzhe Zhou et al. (+3 more)

The realization of multiferroic altermagnets featuring giant intrinsic spin splitting, hold great promise for next-generation spintronics. In this work, based on the recently proposed concept of spin-antiferroelectric (spin-AFE), we construct a class of two-dimensional (2D) multiferroic altermagnets, termed 2D spin-antiferroelectric altermagnets (2D spin-AFEAMs), enabling electrical control of spin polarization via a gate field. Furthermore, we propose a general design strategy for constructing 2D spin-AFEAMs with large intrinsic spin splitting. Guided by this strategy, we predict monolayer $(\mathrm{CoCl})_2\mathrm{Te}$ and its family materials as potential candidates of 2D spin-AFEAM. We uncover a highly tunable transport regime in monolayer $(\mathrm{CoCl})_2\mathrm{Te}$, where the spin current can be switched via the in-plane electric field angle when hole-doped, and via the gate field polarity when electron-doped. Our work enriches the family of 2D multiferroics and provides a blueprint for realizing high-performance, electrically switchable altermagnetic spintronic devices.
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All authors Zesen Fu, Aolin Li, Wenzhe Zhou, Fangping Ouyang, Fawei Zheng, Yugui Yao

Materials Science

Strain-tunable interface electrostatics in Janus MoSSe/silk vdW heterostructure for triboelectric nanogeneration

Deobrat Singh and Raquel Lizarraga

Understanding and engineering interfacial electrostatics in hybrid two-dimensional (2D) and biomolecular material systems is essential for advancing high-performance triboelectric nanogenerators (TENGs). In this work, we systematically investigate the strain-dependent electronic structure and triboelectric response of Janus MoSSe, silk fibroin, and their van der Waals (vdW) heterostructure using first-principles calculations. Tensile strain induces a pronounced band-gap reduction in the MoSSe/silk interface, exceeding that of the isolated constituents and indicating enhanced interlayer electronic coupling. The vdW heterostructure exhibits a significant work-function shift and a substantially larger dipole moment compared to MoSSe and silk alone, revealing strong interfacial charge redistribution driven by Fermi-level alignment and asymmetric polarization. This enhanced polarization directly amplifies the triboelectric surface charge density, producing values more than double those of pristine MoSSe and several orders of magnitude higher than silk. Consequently, the open-circuit voltage and overall triboelectric output are markedly improved across all strain levels. These results demonstrate that synergistic interfacial polarization and strain engineering can effectively elevate charge separation, storage, and transfer efficiencies, establishing the MoSSe/silk vdW heterostructure as a promising material for next-generation high-efficiency TENGs.
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Materials Science · Cross-listed from cs.LG

ReadMOF: Structure-Free Semantic Embeddings from Systematic MOF Nomenclature for Machine Learning

Kewei Zhu, Cameron Wilson, Bartosz Mazur et al. (+3 more)

Systematic chemical names, such as IUPAC-style nomenclature for metal-organic frameworks (MOFs), contain rich structural and compositional information in a standardized textual format. Here we introduce ReadMOF, which is, to our knowledge, the first nomenclature-free machine learning framework that leverages these names to model structure-property relationships without requiring atomic coordinates or connectivity graphs. By employing pretrained language models, ReadMOF converts systematic MOF names from the Cambridge Structural Database (CSD) into vector embeddings that closely represent traditional structure-based descriptors. These embeddings enable applications in materials informatics, including property prediction, similarity retrieval, and clustering, with performance comparable to geometry-dependent methods. When combined with large language models, ReadMOF also establishes chemically meaningful reasoning ability with textual input only. Our results show that structured chemical language, interpreted through modern natural language processing techniques, can provide a scalable, interpretable, and geometry-independent alternative to conventional molecular representations. This approach opens new opportunities for language-driven discovery in materials science.
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All authors Kewei Zhu, Cameron Wilson, Bartosz Mazur, Yi Li, Ashleigh M. Chester, Peyman Z. Moghadam

Materials Science · Cross-listed from cond-mat.stat-mech

Location of the liquid-vapor critical point in aluminum

Xuyang Long and Kai Luo

The precise location of the liquid-vapor critical point in aluminum has remained elusive for decades, with reported critical temperatures spanning nearly 4000 K. Here we resolve this long-standing uncertainty by combining deep potential molecular dynamics with large-scale simulations trained on high-fidelity electronic-structure data. We benchmark multiple exchange-correlation functionals against experimental liquid densities and identify PBEsol as providing the most consistent description. Using complementary approaches – spinodal analysis of the equation of state and direct coexistence simulations with Gaussian mixture phase identification – we converge on a critical temperature of 6531-6576 $^\circ$K, a critical density of $0.637$ g/cm$^{3}$, and a critical pressure of $1.6$ kbar. The precision of these values, with temperature uncertainties of $\sim$50 K, represents a marked improvement over previous estimates. Our framework establishes a transferable strategy for predicting critical phenomena in metals, with implications for laser ablation, shock compression, and planetary modeling under extreme conditions.
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Materials Science

Holonomy-based Diagnostic of Strain Compatibility in Birefringence Imaging of Stress-induced Ferroelectric SrTiO$_3$

Hirotaka Manaka, Kazuma Seike and Yoko Miura

We introduce a holonomy-based geometric diagnostic for birefringence-derived director fields and apply it to stress-induced ferroelectric SrTiO$_3$. Treating the director as a line field in $\mathbb{R}P^2$, we define a holonomy angle $\omega$ from residual rotations accumulated along closed loops in real space and compare it with a conventional local-gradient metric. Whereas the gradient quantifies local orientational variation, $\omega$ probes the global compatibility of rotations along closed paths. The resulting $\omega$ map cannot be reproduced by simple coarse-graining of local gradients, indicating sensitivity to loop-level orientational incompatibility. Analysis of alignment of holonomy rotation axes reveals a cooling-induced reorganization of the electromechanical response, consistent with strain- or stress-related inhomogeneity above the ferroelectric transition and additional ordering below it. These results demonstrate holonomy as a loop-based geometric diagnostic of strain compatibility in orientational fields derived from birefringence.
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Materials Science

The effect of grain boundaries on magnetic exchange interactions in iron

Martin Zelený, Martin Heczko, Petr Šesták et al. (+3 more)

This work investigates how grain boundaries (GBs) modify magnetic exchange interactions in bcc iron, with particular focus on the effect of phosphorus segregation. Using density-functional theory combined with the Liechtenstein-Katsnelson-Antropov-Gubanov Green's-function approach, we calculate Heisenberg exchange parameters for three symmetric tilt GBs, $\Sigma5(310)$, $\Sigma13(510)$, and $\Sigma13(320)$, and use these parameters in Monte Carlo simulations to evaluate finite-temperature magnetic behavior. All clean GBs exhibit strong local deviations from bulk exchange interactions, including antiferromagnetic coupling across the boundary plane. These negative exchange interactions are not governed by interatomic distance alone, but arise primarily from the altered local coordination and symmetry breaking at the GB. Phosphorus segregation, modeled in both substitutional and interstitial configurations at the $\Sigma5(310)$ GB, suppresses the antiferromagnetic couplings and significantly redistributes the local exchange landscape through chemical and electronic effects. Monte Carlo results show that, despite pronounced local perturbations, realistic GB densities cause only a small reduction in the Curie temperature because bulk-like regions dominate the global magnetic transition. A substantial decrease in Curie temperature appears only when the GB volume fraction is artificially increased. The results demonstrate that GBs strongly influence local magnetic interactions while having a limited effect on global magnetic ordering, and they establish a general framework for linking atomistic interfacial structure and chemistry to mesoscale magnetic behavior in Fe-based materials.
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All authors Martin Zelený, Martin Heczko, Petr Šesták, Denis Ledue, Renaud Patte, Miroslav Černý

Saturday 11 April

Materials Science · Cross-listed from cs.HC

SemiConLens: Visual Analytics for 2D Semiconductor Discovery

Kavinda Athapaththu, Shiwei Chen, Yuan Fang et al. (+3 more)

The past few years have witnessed vibrant efforts in discovering new two-dimensional (2D) semiconductor materials from both academia and the industry, due to their promising potential in resolving the severe performance deterioration of traditional semiconductors resulting from condensed silicon thickness. However, existing methods (e.g., Density Functional Theory (DFT) or machine-learning-based approaches) suffer from various challenges such as small datasets, and reliability and trustworthiness issues. To bridge this gap, we propose SemiConLens, a visual analytics approach to combine human expertise with the power of ML to enable effective and reliable 2D semiconductor discovery. Specifically, we first develop a new Correlation Aware Multivariate Imputation (CAMI) method and use ML models like autoencoder, which can better learn from limited data and reveal uncertainty, to address the challenge of sparse data in semiconductivity prediction. Built upon this, our visualization module, consisting of three visualization views with linked interactions, allows material researchers to interactively filter, discover and compare 2D semiconductor candidates. A novel circular glyph design and a new cluster-aware layout optimization approach are proposed to effectively display all the user-configurable key attributes and possible prediction uncertainties of each semiconductor candidate, ensuring a reliable and trustable 2D semiconductor discovery. We assess SemiConLens through quantitative evaluations, expert interviews, and use cases. The results demonstrate SemiConLens's capability to help material researchers conduct effective discovery of desirable 2D semiconductors.
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All authors Kavinda Athapaththu, Shiwei Chen, Yuan Fang, Sanchali Mitra, Yee Sin Ang, Yong Wang

Materials Science · Cross-listed from physics.chem-ph

Inverse Design of Inorganic Compounds with Generative AI

Hannes Kneiding, Lucía Morán-González, Nishamol Kuriakose et al. (+2 more)

Machine learning is revolutionizing chemistry. Beyond the value of predictive models accelerating virtual screening, generative AI aims at enabling inverse design, reversing the compound-to-property prediction paradigm into property-to-compound generation. Chemists now have access to a rich AI toolbox for organic chemistry, including drug discovery. However, the application of these methods to inorganic compounds remains limited by the challenges posed by their intrinsic nature. This Review analyzes how these challenges have been addressed, considering widely diverse systems ranging from molecules to crystals, including transition metal complexes and microporous materials. The analysis focuses on how generative AI methods have evolved towards data-representation-model pipelines that address the full complexity of inorganic compounds, including their chemical composition, geometry, symmetry, and electronic structure. Future directions, like benchmark standardization and the development of synthesizability metrics, are also discussed.
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All authors Hannes Kneiding, Lucía Morán-González, Nishamol Kuriakose, Ainara Nova, David Balcells