Materials Science
Electronic and magnetic properties of the NdNiO$_2$/SrTiO$_3$ thin films
Sajid Sekh, Andrzej Ptok, Wojciech Brzezicki et al. (+2 more)
The hole-doped NdNiO$_2$ layer deposited on the SrTiO$_{3}$ surface exhibits unconventional superconductivity. Here, we present a systematic study of the electronic and
magnetic properties of the NdNiO$_2$
superconductor using the density functional theory (DFT). The strong local Coulomb interactions in the Ni($3d)$ and Nd($4f$) states are included within the DFT+$U$ method. The effect of Sr doping on the electronic band structure and density of states was studied for the NdNiO$_2$ thin films deposited on the SrTiO$_3$ (001) surface. The results obtained for the uncapped thin films were compared with the calculations for the NdNiO$_2$ films capped by the SrTiO$_3$ layer. We have found significant changes in the electronic structure and
magnetic properties of the thin films compared to the bulk
crystal.
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All authors Sajid Sekh, Andrzej Ptok, Wojciech Brzezicki, Przemysław Piekarz, Andrzej M. Oleś
Materials Science
Anisotropic electron-phonon coupling and chiral phonons in van der Waals room temperature ferromagnet Fe$_{5}$GeTe$_{2}$
Smrutiranjan Mekap, Andrzej Ptok, Jyoti Saini et al. (+3 more)
The layered van der Waals Fe$_5$GeTe$_2$ (F5GT) compound exhibits room-temperature ferromagnetism, making it a promising candidate for technological applications. In our study, combined temperature, wavelength, and polarization-dependent Raman measurements, along with ab initio calculations reveal important aspects of
lattice dynamics and electron-
phonon interactions. The angle-resolved Raman intensity under linear polarization configurations exhibits a strong tilt in the laboratory coordinate system, indicating the existence of anisotropic electron-
phonon coupling. The temperature
evolution of this anisotropy is discussed by extracting the phase factor of the Raman tensor elements from the angle-resolved intensity measured at different temperatures, also uncovering a
spin-orbit coupling-mediated electron-
phonon response in F5GT. The thermal
evolution of electron-
phonon coupling is also examined by measuring the temperature dependence of the Fano parameter of the asymmetric peak in the Raman spectra, while wavelength-dependent measurements establish the role of optical resonance in enhancing the anisotropic interaction. Finally, the threefold rotational
symmetry guarantees the existence of
chiral phonons. We present direct spectroscopic evidence for these
chiral vibrational modes through cross-circularly polarized Raman measurements, complemented by theoretical calculations of
phonon circular polarization. Together, these results identify F5GT as an ideal platform for investigating emergent couplings among
lattice, electronic, and
magnetic degrees of freedom and for advancing the understanding of
chiral phonons in
magnetic van der Waals materials.
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All authors Smrutiranjan Mekap, Andrzej Ptok, Jyoti Saini, Changgu Lee, Subhasis Ghosh, Anushree Roy
Materials Science
Topological character of the antiferromagnetic EuMg$_{2}$Bi$_{2}$
Mazharul Islam Mondal, Issam Mahraj, Milo Sprague et al. (+8 more)
Antiferromagnetic EuM$_{2}$Pn$_{2}$ compounds, where M is a metal element and Pn is a pnictogen element, have been recognized as candidates for realizing a topologically nontrivial electronic structure. In this paper, we focus on EuMg$_2$Bi$_2$, whose topological nature still remains unclear. We present a comprehensive study based on several experimental and theoretical techniques.
Magnetic susceptibility, electrical resistivity, and specific heat capacity measurements confirm the existence of an
antiferromagnetic ordering. The electronic band structure was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES), supported by ab initio calculations. ARPES measurement reveals that the electronic structure of this system is dominated by linearly dispersive hole-like bands near the
Fermi level. Theoretical analyses of the electronic band structure indicates that EuMg$_2$Bi$_2$ is a strong topological
insulator, which should be reflected in the presence of a metallic surface state. We also theoretically examine the
magnetic-field-induced anomalous
Hall conductivity, confirming previously reported observations.
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All authors Mazharul Islam Mondal, Issam Mahraj, Milo Sprague, Sabin Regmi, Xiaxin Ding, Firoza Kabir, Himanshu Sheokand, Krzysztof Gofryk, Dariusz Kaczorowski, Andrzej Ptok, Madhab Neupane
Materials Science
Three-dimensional atom-by-atom mapping of nanoscale precipitates in single Te inclusions in Cd0.9Zn0.1Te crystal
Eloïse Rahier, Sebastian Koelling, Guillaume Nadal et al. (+3 more)
The complexity and richness of phenomena governing
alloy crystal growth can be unraveled by examining the three-dimensional atomic-level distribution of elements and
impurities incorporated during growth. These species act as atomic fingerprints, revealing the thermodynamic constraints that shape material structure and composition. Herein, we combine transmission electron microscopy and atom probe of tellurium (Te) inclusions within cadmium zinc telluride (CZT) single
crystals. The correlative analysis uncovers nanoscale precipitates embedded within Te inclusions, consisting of CZT nanocrystals with a Zn content of 1.5 at.%. Surrounding these precipitates, an around 10 nm-thick shell is observed, enriched with copper and indium
impurities. In addition, traces of sodium and sulfur are detected within the nanocrystals. These findings provide direct evidence of the complex segregation and precipitation processes occurring during CZT
crystal growth, reflecting the interplay of thermodynamic driving forces and kinetic constraints that govern solute redistribution. The resulting insights contribute to a deeper understanding of
impurity behavior and phase separation mechanisms in CZT
alloys. This work establishes a framework for modeling and optimization of growth strategies of higher-quality CZT
crystals for next-generation infrared and radiation detection technologies.
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All authors Eloïse Rahier, Sebastian Koelling, Guillaume Nadal, Sudarshan Singh, Luc Montpetit, Oussama Moutanabbir
Materials Science · Cross-listed from cond-mat.supr-con
Metastability and high-Tc superconductivity in A15-type ternary hydride YSbH6 at moderate pressure
Maélie Caussé, Kieran Bozier, Peter I. C. Cooke et al. (+2 more)
The discovery of high-temperature
superconductors remains a central challenge in materials science. Hydrogen-rich compounds are among the most promising candidates, as they can exhibit
phonon-mediated superconductivity at elevated critical temperatures, though their stabilization typically requires extreme pressures. % Here, we report the identification of YSbH$_{6}$ as a promising
superconductor by a multi-stage high-throughput screening on ternary A15-type hydrides, followed by a high-throughput computational search of the Y–Sb–H system, accelerated by ephemeral data derived potentials. % The cubic $Pm\Bar{3}$ YSbH$_{6}$ phase exhibits a predicted critical temperature of 118\,K at 50\,GPa, among the highest $T_{\rm c}$ reported to date for an A15-hydride at this pressure. Thermodynamic analysis shows that YSbH$_{6}$ lies $\sim$100\,meV/atom above the convex hull at 50\,GPa, but only 26\,meV/atom above the hull at 120\,GPa, suggesting possible metastability and synthesis at similar high pressure conditions. The phase is dynamically stable over a wide pressure range (20–120\,GPa), displays kinetic stability at 50\,GPa and elastic stability at 20 and 50\,GPa, key ingredients for long-lived metastable behaviour at moderate pressures. % These results highlight YSbH$_{6}$ as a
benchmark case illustrating the balance between high-$T_{\rm c}$ performance and limited thermodynamic stability in ternary hydrides, and underscore the importance of combined dynamic, thermodynamic, kinetic and elastic stability analyses for guiding experimental synthesis of metastable
superconductors.
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All authors Maélie Caussé, Kieran Bozier, Peter I. C. Cooke, Stefano Racioppi, Chris J. Pickard
Materials Science · Cross-listed from cond-mat.str-el
Semi-automated estimation of hydrogenic initial states for localized Wannier functions
Tatsuki Oikawa, Kota Ido, Takahiro Misawa et al. (+2 more)
We present a semi-automated method for obtaining an initial estimate of Wannier functions, designed to facilitate the construction of Wannier functions for describing low-energy effective models of solids, particularly those relevant to strongly correlated electron systems. Our approach automatically determines the hydrogenic projections orbitals and the center of the Wannier functions from information on Bloch wavefunctions at the $\Gamma$ point. This method is integrated into cif2qewan, enabling seamless generation of input files for
Quantum ESPRESSO and Wannier90. We validate our method through applications to both inorganic and organic compounds, such as Si, SrVO$_3$, FeSe, Na$_8$Al$_6$Si$_6$O$_{24}$, and (TMTTF)$_2$PF$_6$. The obtained results demonstrate that our semi-automated projections give a good initial estimate of the Wannier functions. We also show the comparisons with other methods for estimating the initial states of the Wannier functions, such as the Selected Columns of the Density
Matrix (SCDM). Our methodology shows an efficient way to construct Wannier functions, paving the way for high-throughput calculations in the study of complex materials.
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All authors Tatsuki Oikawa, Kota Ido, Takahiro Misawa, Takashi Koretsune, Kazuyoshi Yoshimi
Materials Science · Cross-listed from physics.chem-ph
Validation of Quantum Computing for Transition Metal Oxide-based Automotive Catalysis
Yuntao Gu, Louis Hector Jr, Paolo Giusto et al. (+4 more)
Quantum computing presents a promising alternative to classical computational methods for modeling strongly correlated materials with partially filled d orbitals. In this study, we perform a comprehensive
quantum resource estimation using
quantum phase estimation (QPE) and qubitization techniques for transition metal
oxide molecules and a Pd zeolite catalyst fragment. Using the binary
oxide molecules TiO, MnO, and FeO, we validate our active space selection and benchmarking methodology, employing classical multireference methods such as complete active space self-consistent field (CASSCF) and N-electron valence state perturbation theory (NEVPT2). We then apply these methods to estimate the
quantum resources required for a full-scale
quantum simulation of a $Z_2Pd$ ($Z=Al_2Si_{22}O_{48}$) fragment taken from the $Pd/2(Al_xSi_{(1-x)})$ catalyst family where x=Si/Al. Our analysis demonstrates that for large Pd zeolite systems, simulations achieving chemical accuracy would require ~$10^6-10^7$ physical
qubits, and range that is consistent with the projected capabilities of future fault-tolerant
quantum devices. We further explore the impact of active space size, basis set quality, and phase estimation error on the required
qubit and gate counts. These findings provide a roadmap for near-term and future
quantum simulations of industrially relevant catalytic materials, offering insights into the feasibility and scaling of
quantum chemistry applications in materials science.
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All authors Yuntao Gu, Louis Hector Jr, Paolo Giusto, Matthew Titsworth, Alok Warey, Dnyanesh Rajpathak, Eser Atesoglu
Materials Science · Cross-listed from physics.chem-ph
Rapid reduction of nitrophenols using reusable magnetic h-BN/Ni–NiO nanocomposites
Anjali Varshney, Ritesh Dubey, Sushil Kumar et al. (+2 more)
The efficient and cost-effective conversion of nitro compounds to amines is crucial for industrial processes and environmental remediation, highlighting the growing demand for earth-abundant metal-based catalysts. In this study,
magnetic Ni–NiO nanostructures and their composites with two-dimensional hexagonal boron nitride (h-BN) were synthesized via a simple and scalable combustion method. The structural, morphological, and compositional properties of the synthesized materials were systematically investigated using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–Vis spectroscopy. The catalytic activity of both Ni–NiO and h-BN/Ni–NiO nanostructures was evaluated using nitrophenol reduction as a model reaction. The h-BN/Ni–NiO nanocomposite exhibited significantly enhanced catalytic performance compared to pristine Ni–NiO, highlighting the synergistic interaction between h-BN and Ni–NiO nanoparticles. Notably, the
magnetic nature of the Ni–NiO core enabled facile recovery of the catalyst using an external
magnetic field, and the composite demonstrated excellent stability and reusability for up to six catalytic cycles with minimal loss of activity. The combination of high catalytic efficiency,
magnetic separability, and structural stability positions the h-BN/Ni–NiO nanocomposite as a promising candidate for green and sustainable catalytic applications, particularly in environmental remediation.
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All authors Anjali Varshney, Ritesh Dubey, Sushil Kumar, Tapas Goswami, Samar Layek
Materials Science · Cross-listed from cond-mat.str-el
2D coherent spectroscopy signatures of exciton condensation in Ta$_2$NiSe$_5$
Jiyu Chen, Jernej Mravlje, Denis Golež et al. (+1 more)
We show that the nonlinear optical response probed by two-dimensional coherent spectroscopy (2DCS) can discriminate between excitonic and
lattice driven order. In the excitonic regime of a realistic model of Ta$_2$NiSe$_5$, the third order 2DCS signals are strongly enhanced by the condensate's amplitude and phase modes, with negligible contributions from single-particle excitations. In the linear optical response, in contrast, single-particle and collective-mode contributions overlap. With increasing electron-
phonon coupling, the amplitude mode contribution to 2DCS initially remains robust, but then drops rapidly and remains small in the
phonon-dominated regime – even in systems with large order parameter. 2DCS also aids the detection of the massive relative phase mode, which is analogous to the Leggett mode in
superconductors. Our analysis, based on the time-dependent Hartree-Fock approach, demonstrates that 2DCS can track the emergence of the
symmetry-broken state and the crossover from Coulomb-driven to
phonon-driven order.
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All authors Jiyu Chen, Jernej Mravlje, Denis Golež, Philipp Werner
Materials Science · Cross-listed from cond-mat.str-el
Kitaev interactions of the spin-orbit coupled magnet UO2
Joseph A. M. Paddison, Lionel Desgranges, Gianguido Baldinozzi et al. (+2 more)
Uranium dioxide, UO$_2$, is a canonical example of a
magnetic material with strong
spin-orbit coupling. Here, we present a study of the
magnetic diffuse scattering measured on a polycrystalline sample of UO$_2$, which we interpret in terms of its
magnetic interactions between U$^{4+}$
magnetic moments. By refining values of the
magnetic interaction parameters to
magnetic diffuse-scattering data measured above the
magnetic ordering transition temperature, we show that the dominant
magnetic coupling in UO$_2$ is a bond-dependent interaction analogous to the Kitaev model of honeycomb magnets. We compare our experimental results with published theoretical predictions and experimental measurements of the
magnetic excitation spectrum. Our results suggest that
magnetic materials with $f$-electron
magnetic ions, particularly actinides, may be promising candidates for realising Kitaev magnetism, and highlight the role that
magnetic diffuse-scattering data can play in identifying such materials.
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All authors Joseph A. M. Paddison, Lionel Desgranges, Gianguido Baldinozzi, Gerard H. Lander, Henry E. Fischer
Materials Science
Enhanced Permittivity in Wurtzite ScAlN through Nanoscale Sc Clustering
James L Hart, Andrew C Lang, Matthew T Hardy et al. (+8 more)
ScN alloyed AlN (ScxAl1-xN, ScAlN) is a wurtzite
semiconductor with attractive ferroelectric, dielectric, piezoelectric, and optical properties. Here, we show that ScAlN films (with x spanning 0.18 to 0.36) contain nanoscale Sc-rich clusters which maintain the wurtzite
crystal structure. While both molecular beam epitaxy (MBE) and sputter deposited Sc0.3Al0.7N films show Sc clustering, the degree of clustering is significantly stronger for the MBE-grown film, offering an explanation for some of the discrepancies between MBE-grown and sputtered films reported in the literature. Moreover, the MBE-grown Sc0.3Al0.7N film exhibits a dispersive and anomalously large dielectric permittivity, roughly double that of sputtered Sc0.3Al0.7N. We attribute this result to the Sc-rich clusters locally reaching x ~ 0.5 and approaching the predicted ferroelectric-to-paraelectric phase transition, resulting in a
giant (local) enhancement in permittivity. The Sc-rich clusters should similarly affect the piezoelectric, optical, and ferroelectric responses, suggesting cluster-engineering as a means to tailor ScAlNs functional properties.
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All authors James L Hart, Andrew C Lang, Matthew T Hardy, Saikat Mukhopadhyay, Vikrant J Gokhale, James G. Champlain, Bethany M. Hudak, Gabriel Giribaldi, Luca Colombo, Matteo Rinaldi, Brian P Downey
Materials Science
Plastic Work Partitioning During Slip- and Twinning-Dominated Deformation in AZ31B Magnesium Alloy
Michał Maj, Sandra Musiał and Marcin Nowak
Plastic work partitioning was investigated in extruded AZ31B magnesium
alloy under loading orientations promoting slip- or twinning-dominated deformation. Slip-dominated deformation exhibits stable plastic flow with approximately 50$\%$ of plastic work dissipated as heat. But twinning-dominated deformation initially stores most plastic work, delaying dissipation and promoting rapid strain hardening and early strain localization. These distinct mechanical responses correlate with microstructural
evolution, \textcolor{black}{showing that, in HCP magnesium
alloys, the energy storage depends on the active deformation mechanism.
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Materials Science
Computational Design of Metal-Free Porphyrin Dyes for Sustainable Dye-Sensitized Solar Cells Informing Energy Informatics and Decision Support
Md Mahmudul Hasan, Chiara Bordin, Fairuz Islam et al. (+4 more)
This study aims to evaluate the optoelectronic properties of metal free porphyrin-based D-$\pi$-A dyes via in-silico performance investigation notifying energy informatics and decision support. To develop novel organic dyes, three acceptor/anchoring groups and five donating groups were introduced to strategic positions of the base porphyrin structure, resulting in a total of fifteen dyes. The singlet ground state geometries of the dyes were optimized utilizing density functional theory (DFT) with B3LYP and the excited state optical properties were explored through time-dependent DFT (TD-DFT) using the PCM model with tetrahydrofuran (THF) as solvent. Both DFT and TD-DFT calculations were carried out using the 6-311G(d,p) basis set. The HOMO energy levels of almost all the modified dyes are lower than the redox potential of I$^-$/I$3^-$ and LUMO energy levels are higher than the conduction band of TiO$2$. The absorption maxima values ranged from 690.64 to 975.55 nm. The dye N1 using triphenylamine group as donor and p-ethynylbenzoic acid group as acceptor, showed optimum optoelectronic properties ($\Delta G{reg}=-9.73$ eV, $\Delta G{inj}=7.18$ eV, $V_{OC}=1.47$ V and $J_{SC}=15.03$ mA/cm$^2$) with highest PCE 14.37%, making it the best studied dye. This newly modified organic dye with enhanced PCE is remarkably effective for the dye-sensitized
solar cells (DSSC) industry. Beyond materials discovery, this study highlights the role of high-performance computing in enabling predictive screening of dye candidates and generating performance indicators (HOMO-LUMO gaps, absorption spectra, charge transfer free energies, photovoltaic metrics). These outputs can serve as key parameters for energy informatics and system modelling.
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All authors Md Mahmudul Hasan, Chiara Bordin, Fairuz Islam, Tamanna Tasnim, Md. Athar Ishtiyaq, Md. Tasin Nur Rahim, Dhrubo Roy
Materials Science
Strain-induced splitting of the CCDW-NCCDW phase transition in 1T-TaS$_2$
M. M. Tyumentsev, V. E. Minakova, N. I. Fedotov et al. (+1 more)
The effects of uniaxial and biaxial tensile strain on the $\rho_{xx}$ and $\rho_{yy}$ components of the resistivity tensor, and the commensurable-nearly commensurate CDW (CCDW-NCCDW) transition temperature in 1T-TaS$_2$ are studied. At room temperature, uniaxial tensile strain increases the resistivity tensor components by a comparable magnitude both parallel and perpendicular to the strain axis. In the case of biaxial strain, up to 20~K decrease in the CCDW-NCCDW phase transition temperature is observed. In the case of uniaxial strain, a new phase with two different CCDW-NCCDW phase transition temperatures is observed, the splitting exceeds 10 K. The occurrence of such a phase is associated with the transition of the CDW into the commensurate state along the tensile strain direction while maintaining nearly commensurability along the perpendicular one. The results allow to justify various models widely used in analysis of transport properties of 1T-TaS$_2$ in commensurate and nearly commensurate states.
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All authors M. M. Tyumentsev, V. E. Minakova, N. I. Fedotov, S. V. Zaitsev-Zotov
Materials Science
Quenching the Non-Collinear Spin Order in High-Tc Layered Ferromagnet Fe5GeTe2
Rabindra Basnet and Ramesh C. Budhani
The realization of long-range
spin order in two-dimensions (2D) has catapulted the search for layered materials with
magnetic ordering above room temperature. These efforts aim to understand and enhance the
spin spin interactions in 2D. An emergent class of such magnets is the layered FeNGeTe2 (N = 3, 4, and 5). Here, we investigate the
magnetic states over a wide field temperature phase space in the high-Tc ferromagnet Fe5GeTe2 using magnetization,
ferromagnetic resonance (FMR), and magneto-transport measurements. Our findings reveal a
magnetic phase transition from a collinear to a complex non-collinear
magnetic order near the temperature T* = 160 K, below which
magnetic susceptibility is reduced, FMR linewidth broadened, and anomalous
Hall resistivity suppressed. Such non-collinearity results from the competition between magnetocrystalline anisotropy and Dzyaloshinskii Moriya interaction arising from the unusual Fe1 ordering in two possible split sites. Our study focuses on the strategy to quench the non-collinear
spin order. Substituting 40% Ni in Fe5GeTe2 is found to be one such quenching strategy. This provides deeper insights into the magnetism of a high-Tc layered-ferromagnet, offering opportunities to develop 2D magnet-based devices.
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Materials Science · Cross-listed from cond-mat.soft
Phase coexistence in thermo-responsive PNIPAM hydrogels triggered by mechanical forces
Noy Cohen
Poly(N-isopropylacrylamide) (PNIPAM) is a temperature-responsive
polymer that undergoes large volumetric deformations through a transition from a swollen to a collapsed state at the volume phase transition temperature (VPTT). Locally, these deformations stem from the coil-to-globule transition of individual chains. In this contribution, I revisit the study of Suzuki and Ishii ("Phase coexistence of neutral
polymer gels under mechanical constraint"), which demonstrated that a PNIPAM rod can exhibit phase coexistence (i.e. comprise swollen and collapsed domains) near the VPTT when subjected to mechanical constraints. Specifically, that paper showed that (1) collapsed domains gradually form in a fixed swollen rod with time and (2) swollen domains can nucleate in a collapsed rod that under uniaxial extension. These behaviors originate from the local thermo-mechanical response of the chains, which transition between states in response to the applied mechanical loading. Here, I develop a statistical-mechanics based framework that captures the behavior of individual chains below and above the VPTT and propose a probabilistic model based on the local chain response that sheds light on the underlying mechanisms governing phase nucleation and growth. The model is validated through comparison with experimental data. The findings from this work suggest that in addition to the classical approaches, in which the VPTT is programmed through chemical composition and network
topology, the transition can be tuned by mechanical constraints. Furthermore, the proposed framework offers a pathway to actively tailor the VPTT through the exertion of mechanical forces, enabling improved control and performance of PNIPAM hydrogels in modern applications.
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Materials Science · Cross-listed from physics.optics
Gap-free Information Transfer in 4D-STEM via Fusion of Complementary Scattering Channels
Shengbo You, Georgios Varnavides, Sagar Khavnekar et al. (+12 more)
Linear phase-contrast scanning transmission electron microscopy (STEM) techniques compatible with high-throughput 4D-STEM acquisition are widely used to enhance phase contrast in weakly scattering and beam-sensitive materials. In these modalities, contrast transfer is often suppressed at low spatial frequencies, resulting in a characteristic contrast gap that limits quantitative imaging. Approaches that retain low-frequency phase contrast exist but typically require substantially increased experimental complexity, restricting routine use. Dark-field STEM imaging captures this missing low-frequency information through electrons scattered outside the bright-field disk, but discards a large fraction of the scattered signal and is therefore dose-inefficient. Fused Full-field STEM (FF-STEM) is introduced as a 4D-STEM imaging modality that overcomes this limitation by combining ptychographic phase reconstruction with tilt-corrected dark-field imaging within a single acquisition. Bright-field data are used to estimate probe aberrations and reconstruct a high-resolution phase image, while dark-field data provide complementary low-frequency contrast. The two channels are optimally fused in
Fourier space using minimum-variance weighting based on the spectral signal-to-noise ratio, yielding transfer-gap-free images with high contrast and quantitative fidelity. FF-STEM preserves the upsampling and depth-sectioning capabilities of ptychography, adds robust low-frequency contrast characteristic of dark-field imaging, and enables dose-efficient, near-real-time reconstruction.
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All authors Shengbo You, Georgios Varnavides, Sagar Khavnekar, Nikita Palatkin, Sihan Shao, Mingjian Wu, Daniel Stroppa, Darya Chernikova, Baixu Zhu, Ricardo Egoavil, Stefano Vespucci, Xingchen Ye, Florian K. M. Schur, Erdmann Spiecker, Philipp Pelz
Materials Science · Cross-listed from cs.AI
VASP Agent: An Agentic Framework for Autonomous First-principles Calculations
Zeyu Xia, Jinzhe Ma, Congjie Zheng et al. (+11 more)
Large
Language Models (LLMs) are increasingly embedded in agentic frameworks for scientific discovery. First-principles materials computation imposes a demanding standard for autonomy: successful execution depends on internally consistent inputs, supervision of long-running calculations, and verified outputs. Here we present VASP
Agent, a coding-
agent-centered system that combines reusable domain skills, deterministic tools, workspace-state inspection, runtime evidence, and scientific guardrails to execute multi-step VASP calculations. The system is evaluated across multiple tasks including structural relaxation, bandgap calculation,
equilibrium lattice constant determination, and CO/Pt(111) adsorption. VASP
Agent completes all evaluated cases, and its computed numerical results are compared with those obtained using pymatgen and other agentic tools. When large deviations occur, the calculation parameters produced by VASP
Agent are more appropriate than those produced by LLM-based workflows. Failure analysis shows that errors that terminate fixed pipelines can be diagnosed and recovered under agentic control.
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All authors Zeyu Xia, Jinzhe Ma, Congjie Zheng, Zhongyao Wang, Shufei Zhang, Yuqiang Li, Hang Su, P. Hu, Changshui Zhang, Xingao Gong, Wanli Ouyang, Lei Bai, Dongzhan Zhou, Mao Su
Materials Science
Tuning Separator Chemistry: Improving Zn Anode Compatibility via Functionalized Chitin Nanofibers
Ibrahim Al Kathemi, Vishnu Arumughan, Mohamed Zbiri et al. (+4 more)
Aqueous zinc (Zn) batteries (AZBs) face significant challenges due to the limited compatibility of Zn anodes with conventional separators, leading to dendrite growth, hydrogen
evolution reaction (HER), and poor cycling stability. While separator design is crucial for optimizing battery performance, its potential remains underexplored. The commonly used glass fiber (GF) filters were not originally designed as battery separators. To address their limitations, nanochitin derived from waste shrimp shells was used to fabricate separators with varying concentrations of amine and carboxylic functional groups. This study investigates how the type and concentration of these groups influence the separator's properties and performance. In a mild acidic electrolyte that protonates the amine groups, the results showed that the density of both ammonium and carboxylic groups in the separators significantly affected water structure and ionic conductivity. Quasi-Elastic
Neutron Scattering (QENS) revealed that low-functionalized chitin, particularly with only ammonium groups, promotes strongly bound water with restricted mobility, thereby enhancing Zn plating and stripping kinetics. These separators exhibit exceptional Zn stability over 2000 hours at low current densities (0.5 mA/cm2), maintaining low overpotentials and stable polarization. Additionally, the full
cell consisting of Zn||NaV3O8.1.5H2O showed a cycle life of over 2000 cycles at 2 A/g, demonstrating the compatibility of the nanochitin-based separators with low concentrations of functional surface groups. These results demonstrate the importance of a simple separator design for improving the overall performance of AZBs.
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All authors Ibrahim Al Kathemi, Vishnu Arumughan, Mohamed Zbiri, Marcel Kröger, Ira Smal, Eero Kontturi, Roza Bouchal
Materials Science · Cross-listed from cond-mat.str-el
Measuring the Hall effect in hysteretic materials
Jaime M. Moya, Anthony Voyemant, Sudipta Chatterjee et al. (+4 more)
Measurement of the
Hall effect is a ubiquitous probe for materials discovery, characterization, and metrology. Inherent to the
Hall measurement geometry, the measured signal is often contaminated by unwanted contributions, so the data must be processed to isolate the
Hall response. The standard approach invokes Onsager-Casimir reciprocity and antisymmetrizes the raw signal about zero applied
magnetic field. In hysteretic materials this becomes nontrivial, since Onsager-Casimir relations apply only to microscopically reversible states. Incorrect antisymmetrization can lead to artifacts that mimic anomalous or topological
Hall signatures. The situation is especially subtle when hysteresis loops are not centered at zero applied field, as in exchange-biased systems. A practical reference for generically extracting the
Hall response in hysteretic materials is lacking. Here, using Co$_3$Sn$_2$S$_2$ as a bulk single-
crystal model that can be prepared with or without exchange-biased hysteresis, we demonstrate two procedures that can be used to extract the
Hall effect: (1) reverse-
magnetic-field reciprocity and (2) antisymmetrization with respect to applied field. We then measure the
Hall effect on CeCoGe$_3$, a noncentrosymmetric antiferromagnet which can be prepared to have asymmetric magnetization and magnetoresistance, and demonstrate how improper processing can generate artificial anomalous
Hall signals. These methods are generic and can be applied to any conductor.
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All authors Jaime M. Moya, Anthony Voyemant, Sudipta Chatterjee, Scott B. Lee, Grigorii Skorupskii, Connor J. Pollak, Leslie M. Schoop
Materials Science
Colloquium: A critique on van der Waals and two-dimensional magnets
Johann Coraux, Nicolas Rougemaille, Cedric Robert et al. (+6 more)
Magnetic two-dimensional (2D)
crystals were isolated about a decade ago, triggering a tremendous research activity worldwide. This colloquium raises a stiff question: what is really new about them? At first sight, they seem to be purer implementations of 2D
spin models than traditional systems such as ultra-thin films. Yet, they partly realized their promises so far, and whether they give fresh perspectives on long-standing predictions in statistical physics is still an open question. Undoubtedly, they are uniquely amenable to electric-field effect, susceptible to mechanical deformation, and sensitive to moirés, for example. They represent interesting platforms for exploring, challenging, or simply revisiting a wide range of phenomena in condensed matter magnetism. This colloquium intends to offer a critical, yet not necessarily skeptical, overview of the field, clarifying what we believe could be unique with 2D magnets, related quasi-2D van der Waals magnets, and their
heterostructures.
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All authors Johann Coraux, Nicolas Rougemaille, Cedric Robert, Clément Faugeras, Andrès Saul, Benoît Grémaud, Luis Hueso, Félix Casanova, Aurélien Manchon
Materials Science
Ab initio prediction of strain-tunable spin defects in quasi-1D TiS3 and NbS3 nanowires
Jordan Chapman, Arindom Nag, Thang Pham et al. (+1 more)
Defects in atomically thin van der Waals materials have recently been investigated as sources of
spin-
photon entanglement with sensitivity to strain tuning. Unlike many two-dimensional materials, quasi-one-dimensional materials such as transition metal trichalcogenides exhibit in-plane anisotropy resulting in axis-dependent responses to compressive and tensile strains. Herein, we characterize the tunable
spin and optical properties of intrinsic vacancy defects in titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires. Within our ab initio approach, we show that sulfur vacancies and divacancies (VS and VD , respectively) in TiS3 and NbS3 adopt strain-dependent defect geometries between in-plane strains of -3 % and 3 %. The calculated electronic structures indicate that both VS and VD possess in-gap defect states with optically bright electronic transitions whose position relative to the conduction and valence bands varies with in-plane strain. Further, our calculations predict that VS in TiS3 and VD in NbS3 exhibit transitions in their ground state
spins; specifically, a compressive strain of 0.4 % along the direction of nanowire growth causes a shift from a triplet state to a singlet state for the VS defect in TiS3, whereas a tensile strain of 2.9 % along the same direction in NbS3 induces a triplet ground state with a zero-
phonon line of 0.83 eV in the VD defect. Our work shows that the anisotropic geometry of TiS3 and NbS3 nanowires offers exceptional tunability of optically active
spin defects that can be used in
quantum applications.
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All authors Jordan Chapman, Arindom Nag, Thang Pham, Vsevolod Ivanov
Materials Science
Anomalous lattice specific heat and rattling phonon modes in quadruple perovskites
Valentin Yu. Irkhin, Zhehong Liu, Danil A. Myakotnikov et al. (+3 more)
Experimental data on the specific heat $C_p$ of quadruple perovskites ACu$_3$Fe$_2$Re$_2$O$_{12}$ (A = Mn, Cu, La, Ce, Dy) are presented, demonstrating an anomalous concave-down $C_p/T$ vs. $T^2$ curve and a bell-shaped feature in $\beta(T) = (C_p - \gamma T)/T^3$ plotted against $T$ on a logarithmic scale. This feature is most pronounced for A = Cu and Mn. These findings can be explained by the rattling phenomenon, previously identified in other systems such as filled skutterudites and $\beta$-pyrochlores. Using first-principles DFT+U calculations, the presence of a rattling mode in A = Mn system is directly confirmed. A qualitative interpretation of the rattling mechanism in terms of a pseudo-Jahn-Teller effect is proposed.
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All authors Valentin Yu. Irkhin, Zhehong Liu, Danil A. Myakotnikov, Evgenia V. Komleva, Youwen Long, Sergey V. Streltsov
Materials Science
Brittle-to-ductile transition and strain relaxation in Si$_{1-x}$Ge$_x$ linearly graded buffers
Riccardo Civiero, Elena Campagna, Afonso Cerdeira Oliveira et al. (+5 more)
The strain-relaxation mechanism of a set of Si$_{0.6}$Ge$_{0.4}$ linearly graded buffers (LGBs), grown following different temperature profiles, has been investigated by means of defect-etching and variable-temperature high-resolution X-ray diffraction (VT-HRXRD). Defect-etching experiments demonstrate that a sharp increase of threading dislocation density (TDD) from $3 \times 10^{5}$\,cm$^{-2}$ to $1.2 \times 10^{6}$\,cm$^{-2}$ takes place when the final growth temperature exceeds a critical value T$_c\approx 530^\circ$C. VT-HRXRD measurements show that in low TDD samples extra relaxation takes place for annealing temperatures larger than T$_c$, thanks to the nucleation of new dislocations. These results indicate that, below T$_c$, strain relaxation is driven by the gliding of existing dislocations while above T$_c$ new dislocations are nucleated, suggesting a link with our results and the brittle-to-ductile transition in Si$_{1-x}$Ge$_x$
alloys.
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All authors Riccardo Civiero, Elena Campagna, Afonso Cerdeira Oliveira, Marvin Hartwig Zoellner, Davide Impelluso, Daniel Chrastina, Giovanni Capellini, Giovanni Isella
Materials Science · Cross-listed from physics.med-ph
Enhanced Vascularity in Gelatin Scaffolds via Copper-Doped Magnesium-Calcium Silicates Incorporation: In-Vitro and Ex-Ovo Insights
Erfan Salahinejad, Avaneesh Muralidharan, Forough Azam Sayahpour et al. (+4 more)
Addressing a critical challenge in current tissue-engineering practices, this study aims to enhance vascularization in 3D porous scaffolds by incorporating bioceramics laden with pro-angiogenic ions. Specifically, freeze-dried gelatin-based scaffolds were infused with sol-gel-derived powders of Cu-doped akermanite (Ca2MgSi2O7) and bredigite (Ca7MgSi4O16) at various concentrations (10, 20, and 30 wt%). The scaffolds were initially characterized for their structural integrity, biodegradability, swelling behavior, impact on physiological pH, and cytocompatibility with human umbilical vein endothelial
cells (HUVECs). The silicate incorporation effectiveness in promoting vascularity was then assessed through HUVEC attachment, capillary tube formation, and ex-ovo chick embryo chorioallantoic membrane assays. The findings revealed significant improvements in both in-vitro and ex-ovo vascularity of the gelatin scaffolds upon the addition of Cu-doped akermanite. The most effective concentrations were determined to be 10 and 20%, which led to notable HUVEC metabolic activity, a well-spread morphology with extensive peripheral filopodia and lamellipodia at 10% and a cobblestone phenotype indicative of in-vivo endothelium at 20% during
cell attachment, the formation of complex networks of tubular structures, and robust vascularization in chick embryo development. Moving forward, the incorporation of Cu-doped akermanite into tissue-engineering scaffolds shows great potential for addressing the limitations of vascularization, especially for critical-sized bone defects, by facilitating the controlled release of pro-angiogenic and pro-osteogenic ions.
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All authors Erfan Salahinejad, Avaneesh Muralidharan, Forough Azam Sayahpour, Maryam Kianpour, Mohsen Akbarian, Daryoosh Vashaee, Lobat Tayebi
Materials Science
Enhanced sinterability and in vitro bioactivity of diopside through fluoride doping
E. Salahinejad and M. Jafari Baghjeghaz
In this work, diopside (CaMgSi2O6) was doped with fluoride at a level of 1 mol.%, without the formation of any second phase, by a wet chemical precipitation method. The sintered structure of the synthesized nanopowders was studied by X-ray diffraction,
Fourier transform infrared spectroscopy and field-emission scanning electron microscopy. Also, the samples' in vitro apatite-forming ability in a simulated body fluid was comparatively evaluated by electron microscopy, inductively coupled
plasma spectroscopy and
Fourier transform infrared spectroscopy. According to the results, the material's sinterability was improved by fluoride doping, as realized from the further development of sintering necks. It was also found that compared to the undoped bioceramic, a higher amount of apatite was deposited on the surface of the doped sample. It is concluded that fluoride can be considered as a doping
agent in magnesium-containing silicates to improve biological, particularly bioactivity, behaviors.
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Materials Science
Stoichiometry-Controlled Structural Order and Tunable Antiferromagnetism in $\mathrm{Fe}_{x}\mathrm{NbSe_2}$ ($0.05 \le x \le 0.38$)
Xiaotong Xu, Bei Jiang, Runze Wang et al. (+4 more)
Transition metal dichalcogenides (TMDs) enable
magnetic property engineering via intercalation, but stoichiometry-structure-magnetism correlations remain poorly defined for Fe-intercalated $\mathrm{NbSe_2}$. Here, we report a systematic study of $\mathrm{Fe}_{x}\mathrm{NbSe_2}$ across an extended composition range $0.05 \le x \le 0.38$, synthesized via chemical vapor transport and verified by rigorous energy-dispersive x-ray spectroscopy (EDS) microanalysis. X-ray diffraction,
magnetic, and transport measurements reveal an intrinsic correlation between Fe content, structural ordering, and
magnetic ground states. With increasing $x$, the system undergoes a successive transition from paramagnetism to a
spin-glass state, then to long-range antiferromagnetism (AFM), and ultimately to a reentrant
spin-glass phase, with the transition temperatures exhibiting a nonmonotonic dependence on Fe content. The maximum Néel temperature ($T_{\mathrm{N}}$ = $\mathrm{175K}$) and strongest AFM coupling occur at $x=0.25$, where Fe atoms form a well-ordered $2a_0 \times 2a_0 $ superlattice within van der Waals gaps. Beyond $x = 0.25$, the superlattice transforms or disorders, weakening Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions and significantly reducing $T_{\mathrm{N}}$. Electrical transport exhibits distinct anomalies at
magnetic transition temperatures, corroborating the
magnetic state
evolution. Our work extends the compositional boundary of Fe-intercalated $\mathrm{NbSe_2}$, establishes precise stoichiometry-structure-magnetism correlations, and identifies structural ordering as a key tuning parameter for AFM. These findings provide a quantitative framework for engineering altermagnetic or switchable
antiferromagnetic states in van der Waals materials.
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All authors Xiaotong Xu, Bei Jiang, Runze Wang, Zhibin Qiu, Shu Guo, Baiqing Lv, Ruidan Zhong
Materials Science · Cross-listed from cond-mat.supr-con
Direct Fabrication of a Superconducting Two-Dimensional Electron Gas on KTaO3(111) via Mg-Induced Surface Reduction
Chun Sum Brian Pang, Bruce A. Davidson, Fengmiao Li et al. (+16 more)
Two-dimensional electron gases (2DEGs) at the surfaces of KTaO3 have become an exciting platform for exploring strong
spin-orbit coupling, Rashba physics, and low-carrier-density superconductivity. Yet, a large fraction of reported KTaO3-based 2DEGs has been realized through chemically complex overlayers that both generate carriers and can obscure the native electronic structure, making spectroscopic access to the underlying 2DEG challenging. Here, we demonstrate a simple and direct method to generate a superconducting 2DEG on KTaO3(111) using Mg-induced surface reduction in molecular-beam epitaxy (MBE). Mg has an extremely low sticking coefficient at elevated temperatures, enabling the formation of an ultrathin (less than 1-2 monolayers) MgO layer that is transparent to soft x-ray photoemission spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES). This allows direct measurement of the surface chemistry and low-energy electronic structure of the pristine reduced surface without the need for a several-nanometer-thick capping layer. XPS shows clear reduction of Ta5+ to lower oxidation states, while ARPES reveals a
parabolic Ta 5d conduction band with an approximately 150 meV bandwidth and additional subband features arising from
quantum confinement. Transport measurements confirm a superconducting transition below 0.7 K. Together, these results demonstrate a chemically straightforward and controllable pathway for fabricating spectroscopically accessible superconducting 2DEGs on KTaO3(111), and provide a powerful new platform for investigating the mechanisms underlying orientation-dependent superconductivity in KTaO3-based
oxide interfaces.
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All authors Chun Sum Brian Pang, Bruce A. Davidson, Fengmiao Li, Mohamed Oudah, Peter C. Moen, Steef Smit, Cissy T. Suen, Simon Godin, Sergey A. Gorovikov, Marta Zonno, Pinder Dosanjh, Sergey Zhdanovich, Giorgio Levy, Matteo Michiardi, Alannah M. Hallas, George A. Sawatzky, Robert J. Green, Andrea Damascelli, Ke Zou