Materials Science · Cross-listed from physics.atom-ph
Disorder-induced nuclear-transition doublet at nominally cubic $^{229}$Th sites
Andrei Derevianko
The $^{229}$Th nuclear clock transition is inhomogeneously broadened even at sites of nominally cubic
symmetry, where the electric-field gradient of the ideal
lattice vanishes. We show that dilute static point-defect disorder produces a doublet with a zero at the quadrupole-free frequency. The doublet is symmetric in the isotropic approximation; size misfit point defects introduce a small lobe asymmetry without removing the zero. Charged and size-misfit defects share inverse-cube scaling and an approximately common normalized profile, whose width separates into a host-controlled background and a term linear in the $^{229}$Th density. In a heavily doped $^{229}$Th:CaF$_2$
crystal [Nature 657, 626 (2026)], the thorium-linked contribution is comparable to the measured 1.1 MHz width; in a lightly doped
crystal [arXiv:2606.08870], the 0.9 MHz width bounds the host background. Neither spectrum shows the predicted dip, which points to the presence of extended defects in both
crystals. If the predicted dip is resolved, it can provide a nuclear-clock discriminator referenced to the quadrupole-free nuclear transition frequency.
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Materials Science · Cross-listed from cond-mat.mes-hall
Reading Altermagnetic Domains with Photon Drag
Sayed Ali Akbar Ghorashi and Andrew M. Rappe
Finite
photon momentum allows second-order photocurrents in centrosymmetric space groups, where the conventional bulk photovoltaic effect is forbidden. Here we study the
photon-drag response of altermagnets and show that its angular dependence reveals both the
symmetry of the
magnetic order and the Néel domain of the sample. For example, when a
crystal rotation exchanges the two domains, the domain-even and domain-odd parts of the current appear in different angular harmonics, $4n$ and $4n+2$ for tetragonal $d$-wave altermagnets, so that two measurements rotated by $90^\circ$ on a single domain isolate the domain-odd current. We also find that these microscopic contributions exhibit opposite domain parities depending on light polarization. Under linear light, only the shift term is domain odd, while under circular light, the domain-odd channel switches to the injection, Fermi-surface, and contact principal-value terms. Mirror
symmetries fix the angular phase of each harmonic and distinguish $d_{x^2-y^2}$, $d_{xy}$, and $g$-wave order. In contrast, conventional collinear antiferromagnets show no domain-odd
photon-drag current, and in tetragonal ferromagnets the two parts share the same harmonics. Although the altermagnetic
spin splitting does not require
spin-orbit coupling (SOC), SOC is essential to observe the domain-odd charge current. Our work uncovers distinct signatures of altermagnetism in
photon drag and provides a route to all optical
magnetic readouts of altermagnets.
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Materials Science
Band Tail States: Speed Bump or End of the Road for Two-Dimensional Semiconductors?
Zherui Han, Robert K. A. Bennett, Davide Donadio et al. (+7 more)
We propose that the path to realizing the full potential of two-dimensional (2D) electronics lies in understanding and mastering their energy band tail states (BTS). Unlike silicon, which benefits from sharp band edges (Urbach energy $E_\rm U$ ~ 10 meV), today's monolayer 2D
semiconductors have rough band edges ($E_\rm U$ ~ 100 meV) caused by spatial potential inhomogeneity. Comparing a physics-based electrical model to experiments, we demonstrate that BTS cause reduced effective mobility and "slow" transistor turn-on with excessive gate voltage in monolayer 2D transistors, which sets a fundamental limit for their energy-efficient operation. We also show that BTS effects in 2D transistors could be mitigated with higher gate capacitance, with strain engineering, and by using bilayer instead of monolayer 2D channels, as long as $E_\rm U$ is reduced below ~ 50 meV. This work provides a theoretical framework and design guidelines to navigate these fundamental limits, and to enable successful integration of 2D
semiconductors into low-power nanoelectronics.
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All authors Zherui Han, Robert K. A. Bennett, Davide Donadio, Maritha A. Wang, Tara Peña, Mikaël Cassé, Martin Vanbrabant, Valeriya Kilchytska, Jean-Pierre Raskin, Eric Pop
Materials Science
Data driven screening of CaCu$_5$-type magnetic structures
Nabaraj Pokhrel, Sheila Whitman and David S. Parker
We develop a machine learning assisted workflow for the rapid screening of permanent magnet candidates within the CaCu$_5$ structure family. We generated more than 60,000 structures through substitutions. These compositions were screened using a combination of pretrained materials models, Materials Project data, and a machine-learning model for magnetization prediction. Four criteria, namely,
metallicity, negative formation energy, energy above the convex hull $\leq 50$~meV/atom, and predicted magnetization above the adopted $\geq 0.75$~T threshold reduced the initial chemical space to 439 candidates for first-principles calculations. Density functional theory calculations revealed that 159 compounds exhibit positive axial
magnetic anisotropy energy, favoring [001] over the tested in-plane directions. The resulting
dataset reveals chemical trends in
magnetic anisotropy across the CaCu$_5$ compositional space and provides a set of candidates for further investigation. More broadly, this work demonstrates a practical strategy for combining existing machine learning models with first-principles calculations to systematically reduce large chemical spaces to tractable sets for computationally intensive materials screening.
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Materials Science
Ceramic Materials: From Atomic Bonding and Processing to Microstructure, Functional Properties, and Biomedical Applications
Jairo Rondon, Juan Valera, Alex Velez Cruz et al. (+1 more)
Ceramic materials are inorganic, predominantly nonmetallic solids whose performance is governed by the interplay among atomic bonding,
crystal structure, processing, microstructure, and functional properties. Their ionic and covalent bonding provides high hardness, thermal and chemical stability, wear resistance, and diverse electrical behavior, but also limits plastic deformation and increases sensitivity to flaws, porosity, grain boundaries, and residual stresses. This review examines ceramics through the processing–microstructure–property–performance relationship, emphasizing the effects of
crystal chemistry, defects, grain size, porosity, and phase stability on mechanical, thermal, electrical, and biological behavior. Conventional sintering, sol–gel processing, and additive manufacturing are discussed as key routes for controlling densification, porosity, geometry, and composition. Biomedical ceramics, including alumina, zirconia, calcium phosphates, hydroxyapatite, tricalcium phosphate, and bioactive glasses, are also reviewed. Emerging topics include nanoceramics, smart ceramics, composites, multimaterial manufacturing, defect engineering, immunomodulatory bioceramics, and sustainable processing. Major challenges remain in brittle fracture, processing heterogeneity, degradation control, scale-up, and the porosity–strength trade-off. Future advances will require integrating advanced manufacturing, multiscale characterization, predictive modeling, and data-driven design.
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All authors Jairo Rondon, Juan Valera, Alex Velez Cruz, Irela Perez Magin
Materials Science
Hierarchical Relaxation in Large-twist-angle Moire Drives Supermoire Formation
Chuqiao Shi, Giovanny Espitia, Yanxing Li et al. (+9 more)
Supermoire
lattices in large-angle twisted bilayers have recently been shown to emerge from periodic arrangements of commensurate stacking motifs, yet the microscopic structural mechanism governing their formation has remained unresolved. Here, we uncover the microscopic origin of supermoire order as a hierarchical
lattice relaxation process. Combining force-field simulations with experimental validation via super-resolution, layer-resolved multislice electron ptychography, our results identify interlayer Se-Se repulsion at the picometer scale as the driving force, giving rise to coupled short-range (about 1 nm) moire relaxation and coexisting long-range (about 10 nm) supermoire modulation. These findings demonstrate that even picometer-scale
lattice relaxation remains critical in large-angle moire systems and must be explicitly considered in understanding their emergent electronic and
quantum phenomena.
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All authors Chuqiao Shi, Giovanny Espitia, Yanxing Li, Yi Jiang, Yiyuan Luo, Xu Qi, Kaiwen Yang, Xiaohui Liu, Xiaoqin Li, Chih-Kang Shih, Mit H. Naik, Yimo Han
Materials Science
Resolving the interfacial mechanical landscape of monolayer NbSe2 grown by confined epitaxy
Ye Wang
Confined epitaxy has recently emerged as a novel methodology for controlled growth of high-quality monolayer two-dimensional (2D) materials. However, mechanistic understanding remains limited to analysing
nucleus adsorption and
diffusion barriers. Here, I discover that van der Waals (vdW) confinement not only affects the specific adsorption and
diffusion of
nuclei on confined substrates but also induces strong coupling to atomic forces at the interface. Using artificial intelligence (AI) assisted density functional theory (DFT) calculations, I study how vdW confinement couples to the atomic motion of monolayer NbSe2 grown between c-plane sapphire and hexagonal boron nitride (h-BN). The calculated force-electronic landscape yields large mechanical forces of +0.070 and -0.04 eV per Angstrom on Nb and Se, respectively, giving rise to a unit-
cell interfacial interaction energy up to 2.4 eV, comparable to reported adsorption and
diffusion energies on similar substrates. The results indicate that interfacial mechanics may explain the success of confined epitaxy. The findings suggest that tuning interfacial mechanics, and related vdW mechanochemistry, could be a promising route to high-throughput, high-quality materials synthesis.
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Materials Science · Cross-listed from cond-mat.str-el
Symmetric Mode Ansatz: Theory of Magnon Collective Modes in Chern Insulators
Miguel Gonçalves, Jonah Herzog-Arbeitman, Juan Felipe Mendez-Valderrama et al. (+3 more)
Moiré materials host integer and fractional Chern
insulators (FCIs) where time-reversal is broken spontaneously by flat band ferromagnetism. In twisted MoTe2, unlike in
quantum Hall, opposite
spins carry opposite Chern numbers and realize Ising ferromagnetism with gapped
magnon excitations. Clarifying the nature of these collective modes and the origin of the
magnon gap is key to understanding the stability of the Chern magnets in these materials. To do so, we develop a generalized single-mode approximation, which we call the symmetric mode ansatz (SyMA), to describe the low-energy
magnon spectrum. We find it to be in exceptional agreement with numerical calculations at integer filling, and qualitatively accurate across fractional fillings including FCIs. To explain the accuracy of the SyMA, we present two families of Hubbard models (including the Haldane model and continuum ideal bands) whose collective modes are analytically solvable and for which the SyMA is either exact or an accurate approximation. For a class of these models where SyMA is exact, we prove two-sided bounds on the zero-momentum
magnon gap in terms of the Chern number, Berry
curvature, and
quantum metric, revealing that uniform
quantum geometry is sufficient for stabilizing magnetism in Chern bands.
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All authors Miguel Gonçalves, Jonah Herzog-Arbeitman, Juan Felipe Mendez-Valderrama, Andreas Feuerpfeil, B. Andrei Bernevig, Nicolas Regnault
Materials Science · Cross-listed from cs.LG
PXtal: Learning to Align Powder X-Ray Diffraction and Crystal Structures under Information Asymmetry across Modalities
Zhuoran Yang, Christopher M. Collins, Bei Peng et al. (+3 more)
Scientific
multimodal learning commonly assumes that paired views are comparably informative. Powder X-ray diffraction (PXRD) makes this mismatch explicit: compressing a three-dimensional
crystal structure into a one-dimensional diffraction pattern loses information and makes the pattern harder to connect to the
crystal structure that produced it. We introduce PXtal, a framework for learning aligned PXRD and
crystal representations under this physically imposed information asymmetry. PXtal uses Unbalanced Optimal Transport (UOT) to adapt the cross-modal coupling and coupling-level generalized Kullback-Leibler (GKL) divergence to supervise the full transport plan. Across six test sets, including four zero-shot transfer sets, PXtal consistently outperforms the baseline models in PXRD-to-
crystal candidate
retrieval, with the largest gains when PXRD patterns have close but crystallographically distinct nonpaired neighbors, meaning similar input patterns associated with different
crystals. The resulting
crystal and PXRD encoders transfer more effectively to downstream materials and crystallographic tasks. These results identify information asymmetry as a general design problem in scientific
multimodal learning:
alignment objectives should reflect what each modality preserves.
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All authors Zhuoran Yang, Christopher M. Collins, Bei Peng, Luke M. Daniels, Matthew J. Rosseinsky, Vladimir V. Gusev
Materials Science
Magnetic Order from First-Principles Linear Response
Yaroslav Zhumagulov, Emiliano Cruz-Aranda, Denis Kochan et al. (+1 more)
The
magnetic order of a material is usually predicted by comparing the energies of trial
spin configurations, a strategy that cannot reach orders outside the chosen set and rapidly becomes intractable as the number of
magnetic sites grows. We show that the order can instead be identified directly from the paramagnetic state: the leading eigenmodes of its self-consistent magnetization response, obtained with
spin–orbit coupling at arbitrary wavevector within the primitive
cell, determine both the ordering wavevector and the pattern of moments, with no candidate configurations. With no prior assumption about the order, the method correctly reproduces the G-type stacking with out-of-plane moments in the altermagnet candidate KV$_2$Se$_2$O, the $3{:}1$ ferrimagnetic tetrahedra of Cu$_2$OSeO$_3$, and the incommensurate spiral instability of monolayer NiI$_2$. Our results establish the response of the paramagnetic state as a predictive and unbiased route to assessing
magnetic order, enabling systematic searches for complex magnets.
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All authors Yaroslav Zhumagulov, Emiliano Cruz-Aranda, Denis Kochan, Oleg V. Yazyev
Materials Science
Interface Doping Mechanism of p-Type Conductivity in Mist-CVD-Grown LiGa5O8 Thin Films
Dong Su Yu, Shashu Tomar, Zixiu Huang et al. (+7 more)
LiGa5O8 is an ultrawide-bandgap oxide
semiconductor that has recently been experimentally demonstrated to exhibit p-type conductivity; however, the origin of the observed p-type transport remains poorly understood. In this work, we investigate the origin of p-type conductivity by systematically comparing the electrical, compositional, and structural properties of mist chemical vapor deposition (mist-CVD) grown LiGa5O8 thin films exhibiting either p-type conductivity or insulating behavior under different growth conditions. The p-conductive films exhibit room-temperature hole concentrations on the order of 10^18 cm^-3. The emergence of p-type conductivity is found to be strongly correlated with the elemental composition of the films, with X-ray photoelectron spectroscopy (XPS) revealing a reduced Li/Ga ratio in the p-conductive films, indicative of a Li-deficient composition. Raman spectroscopy and X-ray diffraction (XRD) further reveal signatures of e̱ta}-Ga2O3 in the p-conductive films that are absent in the insulating films, demonstrating the formation of a secondary e̱ta}-Ga2O3 phase. Considering the reported type-II band
alignment between LiGa5O8 and e̱ta}-Ga2O3, together with theoretically predicted acceptor levels associated Li vacancies (V_Li) in LiGa5O8, the formation of mixed LiGa5O8/e̱ta}-Ga2O3 phases is proposed to facilitate electron transfer from the e̱ta}-Ga2O3 valence band to acceptor states in LiGa5O8, thereby promoting hole accumulation and p-type conductivity.
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All authors Dong Su Yu, Shashu Tomar, Zixiu Huang, Kaitian Zhang, Sarker Md. Sadman, Vijay Gopal Thirupakuzi Vangipuram, Ye Lin, Walter R. L. Lambrecht, Roberto C. Myers, Hongping Zhao
Materials Science
Electronic Structure Descriptors for CO$_2$ Conversion Activity in Perovskite Oxides
Hyo-sun Jin, Jiyeon Kim and Sooran Kim
Electronic structure descriptors have been widely used to rationalize catalytic activity, but their application to CO$_2$-to-CH$_4$ conversion in perovskite oxides remains relatively limited. Here, we investigate six electronic structure descriptors related to band centers and bandwidths. We find that the unoccupied transition-metal (TM) $3d$-band center, charge-transfer energy, and the ratio of the unoccupied TM $3d$ to occupied O $2p$ bandwidths, $W_{3d}/W_{2p}$, exhibit negative correlations with CH$_4$ activity. These qualitative trends are further quantified using a parametric brute-force searching (BFS) approach to obtain explicit fitting equations. Notably, the selected equations depend only on $W_{3d}/W_{2p}$, providing an electronic structure perspective on the enhanced activity in double perovskites. We apply the selected equation to screen 24 La-based double perovskites. This screening suggests that La$_2$CoGaO$_6$, La$_2$CoAlO$_6$, and Ti-containing compositions are promising candidates. The present approach can help identify descriptor-activity relationships and guide materials screening in perovskite oxides.
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Materials Science
Prediction of the thermal neutron response of grain-boundary impedance in Gd-doped ceria based on the radiation-ionic effect
Zhongming Zhang
The radiation-ionic effect was recently reported in 3 mol% Gd-doped CeO$_2$ (3GDC): under $^{60}$Co gamma irradiation at 35 Gy/min, the grain-boundary (GB) ionic resistance of a bulk pellet decreased 680-fold at room temperature, because electrons trapped at the GB core lower the space-charge potential. The effect has been demonstrated only with
photons. Gd has the largest thermal-
neutron capture cross section of any stable element and is also the dopant that creates the GB barrier in GDC, so the same mechanism could link GB impedance to thermal-
neutron sensing; whether it does, and under what conditions, has not been examined. Here the thermal-
neutron response of 3GDC is modelled with the gamma-calibrated Mott-Schottky/Seager framework, with unmeasured parameters carried as intervals and propagated jointly. Each capture deposits about 50 keV by conversion and Auger electrons within 1 $\mu$m, the remaining 8 MeV leaving as
prompt photons; Gd segregation to the GBs adds a factor of only 1-2 because the electron range exceeds the grain size. A thermal flux of $8\times10^{9}$ cm$^{-2}$s$^{-1}$ (6-12$\times10^{9}$) matches the GB-effective generation rate of the 35 Gy/min calibration, and the predicted room-temperature GB resistance ratio is 110 (70-170) at $10^{9}$ and 970 (600-1500) at $10^{10}$ cm$^{-2}$s$^{-1}$, falling to 2 at 61 (55-68) and 81 (73-92) $^\circ$C. The
neutron case differs from gamma irradiation in three respects: capture events are discrete, so the continuous-source approximation depends on the unmeasured trapped-charge lifetime; self-shielding (mean free path 0.27 mm) makes the response thickness dependent; and capture
photons absorbed in the pellet add a gamma term comparable to the local term for pellets of 0.3 mm or more. The intervals are conditional on the model and exclude its structural error. The conditions under which the prediction can be tested are given.
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Materials Science
Lattice dynamics of disordered phases of silicon and spatially resolved computations of thermal conductivity
A. Gautam, C. Ugwumadu, L. A. M. Rosset et al. (+3 more)
The
lattice dynamics of disordered systems (amorphous solids,
polymers and glasses) are often distinct from crystalline analogues. Examples include the "two-level systems" and the
Boson peak. Here, we show that even the venerable material amorphous silicon offers new wrinkles: (1) realistic networks studied with DFT-quality interatomic potentials show the existence of harmonic modes exhibiting anomalously large root-mean-square variation in atomic positions, and (2) these dynamics determine the processes of heat transport. We correlate the atomic dynamics with transport using the site-projected thermal conductivity [C. Ugwumadu et. al Phys. Status Solidi B 263, e202500316 (2026)], and
conjecture that these observations are relevant to other disordered systems.
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All authors A. Gautam, C. Ugwumadu, L. A. M. Rosset, R. M. Tutchton, S. Nakhmanson, D. A. Drabold
Materials Science
Surface Physics of Low-Dimensional Pnictogen Chalcohalides and Its Impact on Photovoltaic Technologies
Cibrán López, David Rovira, Álex Jiménez-Arguijo et al. (+3 more)
Low-dimensional pnictogen chalcohalides (MChX; M = Bi, Sb; Ch = S, Se; X = I, Br) are promising non-toxic
semiconductors for solar energy conversion, yet the power conversion efficiencies of MChX solar
cells remain below 10%, far from their Shockley-Queisser limit of $\sim$30%. Efficient charge extraction depends critically on the band-edge
alignment between the absorber and the charge-selective contacts, which is a surface property. Here, we combine first-principles calculations with device-level modelling to investigate the surface energetics and band
alignments across the MChX family. An exhaustive sampling of
crystal orientations, including low-
symmetry facets, identifies the (011) and (010) surfaces as the most stable terminations in all eight compounds. Their formation energies differ by only $\approx 0.01$-$0.03\mathrm{J\,m^{-2}}$, yet their band edges are shifted rigidly with respect to each other by up to $0.8$eV. Drift-
diffusion simulations of BiSBr show that the coexistence of such facets can reduce the open-
circuit voltage by up to $0.6$V, even in an otherwise ideal, defect-free absorber. Surface orientation thus emerges as a hidden design parameter for charge extraction. This study may help to explain the gap between the theoretical and experimental efficiencies of MChX solar
cells, and it provides new design principles for MChX-based photovoltaic and photocatalytic technologies.
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All authors Cibrán López, David Rovira, Álex Jiménez-Arguijo, Zacharie Jehl, Edgardo Saucedo, Claudio Cazorla
Materials Science · Cross-listed from physics.geo-ph
Quantification of plastic deformation in anorthite using micropillar compression
Sarah Incel, Chunhua Tian, Anja Schreiber et al. (+2 more)
Plagioclase is the most abundant mineral group of the crust and will therefore either control or strongly influence crustal rheology. Yet, we still know little about
crystal plasticity in plagioclase as brittle deformation dominates under most laboratory conditions. To overcome past challenges in quantifying
crystal plastic deformation in plagioclase, we used micropillar compression to quantify the strength of specific slip systems as well as the stresses necessary for mechanical twinning in anorthite. Pillars with diameters of around 1 micrometre were milled from three differently oriented cuts of the same anorthite single
crystals using focused-ion beam. Uniaxial deformation of 36 pillars in total was then conducted inside a scanning-electron microscope under either 25, 300, or 800 degrees Celsius. Most pillars were deformed with a constant displacement rate that corresponds to a strain rate of around 0.001 1/s on the pillars. We find that the critical resolved shear stress (CRSS) for mechanical (pericline) twinning lies at around 300 MPa and is, as expected from previous studies on other materials, insensitive to changes in temperature or strain rate. Pillar deformation in
crystals oriented to activate slip exhibit a strong decrease in yield stress with increasing temperature. Among the deformation mechanisms active during pillar deformation, twinning is the easiest under the applied conditions, followed by slip on (011)[100] regardless of temperature. Slip on (011)[0-11] or (0-11)[011] is consistently the hardest mechanism to activate in our anorthite pillars.
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All authors Sarah Incel, Chunhua Tian, Anja Schreiber, Vladimir Roddatis, Sandra Korte-Kerzel
Materials Science
Universal orbital-coupling rules for hydrogen-defect interactions in bcc metals
Qianxi Zhu, Hao-Xuan Huang, Zichen Zhang et al. (+2 more)
Hydrogen-defect interactions control the performance of body-centered-cubic (bcc) metals. However, the complex variations among defects lead to various empirical models that lack transferability across defects. Here, we propose an orbital-coupling model, built on coordination number and interatomic distance, that quantifies the H solution energetics across nanovoids, vacancy loops and grain boundaries in bcc metals, and even predicts the potential-energy surfaces of H at nanovoids. Our model reveals an unconventional s-d coupling rule in the confined environment of defects: H-metal interactions exhibit a unique coordination-dependent law, whereas H-H interactions, deviating from the usually speculated s-s coupling, acquire the distance-decay law of H-metal coupling. This unusual rule proves essential to reproduce the experimentally observed bimodal profile of H desorption. Our electronic-structure-origin, unified model is thus crucial to understanding the nature of chemical bonds under constraint and engineering the H-tolerant materials.
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All authors Qianxi Zhu, Hao-Xuan Huang, Zichen Zhang, Hong-Bo Zhou, Wang Gao
Materials Science
Solphin: Photovoltaic efficiency analysis for bulk materials using Python
Philippa U Cox, Peter P Russell, Andrea Crovetto et al. (+3 more)
In the development of photovoltaic materials, computational simulation has become a important tool for reducing the time and cost of exploring novel materials, as well as providing insights that help drive improvements in efficiency through increasing fundamental understanding. We present Solphin, a Python package for the generation, post-processing and analysis of photovoltaic calculations from periodic solid state Density Functional Theory. We include the ability to calculate the photovoltaic Figure of Merit, detailed balance and spectroscopic limited maximum efficiency, alongside other analysis methods. Solphin has been built to improve the access, reproducibility and ease of evaluating the photovoltaic potential of a material in an efficient and user-friendly manner.
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All authors Philippa U Cox, Peter P Russell, Andrea Crovetto, Alexander G Squires, Louie Slocombe, David O Scanlon
Materials Science
Screening of tensor properties by magnetic point group symmetries: The PythMPG code package
Andrea Urru, Turan Birol, Trey Cole et al. (+1 more)
Understanding the
symmetry requirements that permit specific phenomena or physical effects is crucial in condensed matter physics for identifying candidate materials that exhibit one or more of these effects. To this end, screening tensor properties based on (
magnetic) point-group
symmetries is of particular interest. Here, we present the PythMPG code package, a tool designed for this purpose. Inspired by the MTENSOR utility of the Bilbao Crystallographic Server, PythMPG performs
symmetry analysis in a self-contained way to determine which tensors, characterized by their Jahn symbols, are allowed for each
magnetic point group and how many
symmetry-allowed independent components each tensor possesses. We describe the structure of the code and present some illustrative examples.
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All authors Andrea Urru, Turan Birol, Trey Cole, David Vanderbilt
Materials Science
Origins of Universal Machine Learning Force-Field Errors in Multicomponent Materials
Hongwei Du, Dingyang Lv, Baole Wei et al. (+11 more)
Universal machine learning force-field generalization to multicomponent environments generated by compositional design remains insufficiently assessed. We construct a
benchmark of 7,599 multicomponent configurations inspired by high-
entropy design, elemental substitution and anion mixing. Eleven pretrained models are evaluated against density functional theory for energies, forces and stresses, with assessment extended to elastic, vibrational and adsorption-related properties. Force errors are analysed through training-reference coverage, local
geometric heterogeneity, distance directionality and elemental response. Distances to training-reference environments reveal a qualitative association between coverage differences and increasing errors, while substantial variation remains at similar distances. Higher-error groups show greater local
geometric heterogeneity, although OMat24 provides broad coverage of these environments. Relative to training-reference pair medians, errors remain low near the median, rise steeply on the compression side and increase more weakly on the extension side. After matching element pairs and absolute distance deviations, compression-side force errors are 1.81-1.95 times extension-side errors. Model-predicted pairwise interaction curves show greater
curvature under compression. Fitting difficulty in independent elemental systems correlates with electronic band-energy responses to atomic displacements and Fermi-level shifts, and a similar pattern is observed in multicomponent systems. In parameter-matched comparisons, spherical-harmonic representations with maximum degrees of 2 and 4 lower test force errors for 38 and 40 of 43 elements, respectively, while differences in elemental difficulty remain. These findings inform force-field selection for experimental compositional design and identify targets for training-data sampling and model representations.
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All authors Hongwei Du, Dingyang Lv, Baole Wei, Yu Ren, Feng Yu, Xin He, Bonan Zhu, Jiahui Liu, Yongda Huang, Yongheng Li, Jianjun Liu, Siqi Shi, Hong Wang, Ziheng Lu
Materials Science
Electronic Properties of Ladder-Type Phenylenes Studied by Thermally-Assisted-Occupation Density Functional Theory
Tsu-Hsuan Wang and Jeng-Da Chai
Accurate prediction of the electronic properties of extended $\pi$-conjugated systems with radical character remains a major theoretical challenge. To overcome this challenge, thermally-assisted-occupation density functional theory (TAO-DFT) has been developed in recent years. In this study, we employ TAO-DFT to systematically explore the electronic properties of ladder-type phenylenes ($n$-LPs), containing $n$ linearly fused four-membered carbon rings. Our calculations reveal that all investigated $n$-LPs (with $n$ = 1 ~ 40) possess singlet ground states. With increasing $n$-LP length, we observe a transition from the nonradical character of shorter $n$-LPs to the polyradical character of longer $n$-LPs. Notably, we identify a distinct damped periodic oscillation in the radical character of $n$-LPs, featuring highly correlated hotspots at specific lengths ($n = 3k - 1$, where $k$ are positive integers). The real-space representation of active orbitals confirms this global electronic behavior is governed by the intrinsic structural periodicity and completely delocalized nature of the active orbitals along the central ladder framework. These findings provide fundamental insights into the size-dependent electronic properties of $n$-LPs, guiding their rational design for future nanomaterial applications.
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Materials Science
Anomalous Hall enhancement in fully compensated non-collinear antiferromagnetic Cr-doped Mn3Sn
Ying Zhang, Xin Chen, Hang Xie et al. (+3 more)
The non-collinear antiferromagnet (AFM), Mn3Sn, exhibits ultrafast
spin dynamics and negligible stray fields, making it a promising candidate for fast and energy-efficient spintronic devices. However, its practical applications remain limited by the relatively small Hall response compared with ferromagnets. Here, we demonstrate through both first-principles calculations and experiments that Cr-doping is a promising strategy to enhance the anomalous Hall transport in Mn3Sn without breaking the antiferromagnetic order. Our first-principles calculations reveal an effective Cr-doping window that enhances the anomalous Hall conductivity while largely preserving the host coplanar inverse triangular AFM order. Berry
curvature and Wannier
Hamiltonian analyses further reveal that Cr substitution amplifies the pre-existing Berry
curvature hotspots through coordinated changes in the energy
alignment, local interband gap, and Mn-derived orbital weight of the relevant bands. Experimentally, we have found that Cr doping not only supports our computational predictions (enhancement of the anomalous Hall conductivity), but also suppresses the transition to helical or
spin-glass phases at low temperatures. These findings demonstrate that Cr-doping is an effective strategy for stabilizing the AFM order while simultaneously improving the anomalous Hall transport properties over a wide temperature range in Mn3Sn.
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All authors Ying Zhang, Xin Chen, Hang Xie, Ziyan Luo, Yihong Wu, Lei Shen
Materials Science
Ab-initio Investigation on h-Be3N2 Monolayer for Photocatalytic Hydrogen Evolution Reaction and Oxygen Evolution Reaction
Karan Patel, Hetvi Jadav and Himanshu Pandey
In this work, we have systematically investigated the structural stability, electronic properties, and photocatalytic performance of the 2D h-Be3N2 monolayer for water splitting application, utilizing a first-principles density functional theory. Electronic structure calculations based on the PBE functional reveal that h-Be3N2 is a direct band-gap
semiconductor with a band gap value of 1.74 eV, making it well suited for visible-light-driven photocatalysis. Furthermore, the
alignment of band-edges illustrates that h-Be3N2 has suitable redox potential that facilitate overall photocatalytic water splitting in neutral and alkaline environment. Conversely, in acidic condition, the position of valence band is an adequate to enable the OER, thereby leading to photocathodic behavior. At neutral pH, the HER process is still possible with the application of an external potential of 0.77 V. For the OER process, it is thermodynamically favourable only under strongly alkaline conditions, while an external potential of 0.43 V is needed to promote the reaction at neutral pH. These results clearly underscore the significant impact of solution pH and photogenerated charge carriers on the photocatalytic effectiveness of the h-Be3N2 monolayer. Furthermore, the study of H coverage indicates that the amount of H that adheres to the surface has a considerable impact on the efficiency of the HER in h-Be3N2. The favourable photocatalytic capabilities of the h-Be3N2 monolayer imply that it might be a viable option for upcoming solar-powered green hydrogen generation and may assist in realizing the goals of the National Green Hydrogen Mission by facilitating effective and sustainable hydrogen production.
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