Materials Science · Cross-listed from physics.bio-ph
Drug-delivery Ca-Mg silicate scaffolds encapsulated in PLGA
A. Jadidi, E. Salahinejad, E. Sharifi et al. (+1 more)
The aim of this work is to develop dual-functional scaffolds for bone tissue regeneration and local antibiotic delivery applications. In this respect, bioresorbable bredigite (Ca7MgSi4O16) porous scaffolds were fabricated by a foam replica method, loaded with vancomycin hydrochloride and encapsulated in poly lactic-co-glycolic acid (PLGA) coatings. Field emission scanning electron microscopy, Archimedes porosimetry and
Fourier-transform infrared spectroscopy were used to characterize the structure of the scaffolds. The drug delivery kinetics and cytocompatibility of the prepared scaffolds were also studied in vitro. The bare sample exhibited a burst release of vancomycin and low biocompatibility with respect to dental pulp stem
cells based on the MTT assay due to the fast bioresorption of bredigite. While keeping the desirable characteristics of pores for tissue engineering, the biodegradable PLGA coatings modified the drug release kinetics, buffered physiological pH and hence improved the
cell viability of the vancomycin-loaded scaffolds considerably.
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All authors A. Jadidi, E. Salahinejad, E. Sharifi, L. Tayebi
Materials Science · Cross-listed from physics.bio-ph
Competition of carrier bioresorption and drug release kinetics of vancomycin-loaded silicate macroporous microspheres to determine cell biocompatibility
A. Bolandparvaz Jahromi and E. Salahinejad
Bioceramic porous microspheres are promising substances for dental and orthopedic bone void filling, tissue engineering and drug delivery applications. In this research, the structure and cytocompatibility of bioactive magnesium-calcium silicate macroporous microspheres loaded with vancomycin hydrochloride, an antibiotic drug, were studied. In this regard, bredigite (Ca7MgSi4O16), akermanite (Ca2MgSi2O7) and diopside (CaMgSi2O6) carriers were fabricated through a sequence of sol-gel, calcination, droplet extrusion and sintering processes, followed by impregnated with vancomycin. X-ray diffraction (XRD) and scanning electron microscopy verified the formation of the desired ceramic crystalline phases and macroporous characteristics of the carriers, respectively. Based on the MTT assay, the antibiotic-loaded bredigite, akermanite and diopside devices comparatively exhibited the lowest, intermediate and highest levels of human bone marrow mesenchymal stem
cells (hBM-MSCs) viability and proliferation, respectively. It was concluded that the role of the carrier bioresorption kinetics prevails over the drug delivery kinetics in determining the
cell biocompatibility of the devices.
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Materials Science · Cross-listed from cond-mat.str-el
K$_2$Co$_2$(TeO$_{3}$)$_{3}$ $\cdot$ 2.5 H$_2$O : A mineral-inspired pseudo-honeycomb cobalt dimer antiferromagnet
Austin M. Ferrenti, Maxime A. Siegler, Yiqing Hao et al. (+9 more)
In recent years, magnetically-frustrated triangular and honeycomb
lattice cobaltates have seen extensive study in the pursuit of a
quantum spin liquid (QSL) state in a real material. In this work, we describe the hydroflux synthesis of K$_2$Co$_2$(TeO$_{3}$)$_{3}$ $\cdot$ 2.5 H$_2$O (KCoTOH), a novel zemannite-type antiferromagnet (AFM) possessing structural elements of both triangular dimer and honeycomb structural motifs. Bulk magnetometry and specific heat data support the onset of long-range AFM order below $T_\text{N}$ = 7.6(1) K, with
neutron diffraction and
muon spin relaxation ($\mu$SR) measurements placing the majority of the ordered moment within the pseudo-honeycomb plane. We resolve three unique oscillation frequencies from the zero-field $\mu$SR spectra, additionally suggesting a remarkably low level of structural disorder in as-grown KCoTOH
crystals. Whereas interactions between dimerized chains of Co$^{2+}$ cations are typically observed to be negligible or
ferromagnetic in nature, the largely planar ordering motif observed in KCoTOH is instead stabilized by net
antiferromagnetic interactions through bridging tellurite groups. This work highlights the potential of hydroflux synthesis methods in the stabilization of
magnetic materials possessing novel and potentially more frustrated
lattice geometries.
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All authors Austin M. Ferrenti, Maxime A. Siegler, Yiqing Hao, Chris Lygouras, Tong Chen, Tiffany A. Soetojo, Megan R. Rutherford, Kenji M. Kojima, Huibo Cao, Natalia Drichko, Alannah M. Hallas, Tyrel M. McQueen
Materials Science
Quantitative 3D Analysis of Porosity and Fractal Geometry in Electrochemically Etched Macroporous Silicon
A. Ramírez-Porras, I. Prado, N.R. Schwarz et al. (+1 more)
Macroporous silicon is widely employed in sensing and optoelectronic applications due to its large internal surface area and adjustable pore structure. However, quantitative correlations between morphology and functionality require accurately characterizing the three dimensional pore network. In this study, we used focused Ga+ ion beam scanning electron microscopy
tomography to reconstruct representative volumes of electrochemically etched macroporous silicon layers. We extracted true three dimensional porosity and surface-to-volume ratios and compared them with two-dimensional estimates obtained from SEM images. Our results demonstrate that surface-based porosity systematically underestimates true volumetric porosity. These discrepancies arise from anisotropy, branching, and variability in pore size. Fractal analysis reveals that the pore network has moderate
geometric complexity, consistent with electrochemical macropore formation mechanisms. The results highlight the importance of direct 3D characterization for reliable morphological quantification and provide a robust framework for interpreting structural trends in macroporous silicon.
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All authors A. Ramírez-Porras, I. Prado, N.R. Schwarz, U. Steiner
Materials Science · Cross-listed from physics.app-ph
Blue Organic Light-Emitting Diodes with External Quantum Efficiencies over 20% Based on Europium(II) Emitters
Mahmoud Soleimani, Toni Bärschneider, Felix Kaden et al. (+4 more)
The realization of blue electroluminescence with high efficiency and lifetime remains a long-standing hurdle for organic light-emitting diode (OLED) technology to overcome. Divalent Europium [Europium(II)] complexes offer a fundamentally distinct pathway toward this goal, as their atomic 4f-5d transitions yield single-Gaussian, spectrally pure emission with theoretical 100%
exciton utilization in electroluminescence and no involvement of fragile organic bonds in the emissive process. Here, we present a rigid aza-crown europium(II) complex (Eu5NHCrown) that achieves near-unity photoluminescence
quantum yield with bright, pure-blue emission and its incorporation in OLEDs. The emitter complex sublimes without decomposition and can be processed by industry-standard
vacuum deposition. A bottom-emitting, single-host OLED architecture delivers an external
quantum efficiency (EQE) of 20.7% with minimal roll-off (19.3% at 1000 cd m${}^{-2}$ ) and a narrowband electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.12, 0.25). This ligand design provides enhanced steric shielding of the Eu(II) center, enabling the highest reported efficiency among
vacuum-deposited Eu(II)- based blue OLEDs while maintaining performance at high luminance. These results reveal the true potential of divalent Europium 4f-5d transitions for high-efficiency blue OLEDs, establishing a molecular design concept that bridges atomic-transition efficiency with the processability of organic materials.
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All authors Mahmoud Soleimani, Toni Bärschneider, Felix Kaden, Roman Tkachov, Sebastian Schellhammer, Sebastian Reineke, Carsten Rothe
Materials Science · Cross-listed from physics.app-ph
High-Efficiency Deep Blue Single-Gaussian Europium(II) Emitters and their Emitter-Host Interactions
Mahmoud Soleimani, Paulius Imbrasas, Jan-Michael Mewes et al. (+6 more)
Eu(II) complexes are attractive emitters for deep-blue organic light-emitting diodes (OLEDs) due to their narrow, parity-allowed 4f-5d emission; however, their implementation in
vacuum-processed OLEDs has remained limited. Here, we introduce a new molecular design concept for Eu(II) emitters, in which a crown-ether ligand is combined with carborate anions to define the coordination environment and improve steric shielding of the europium center. Based on this design, we present two emitters that combine narrow deep-blue photoluminescence with
quantum yields approaching 90% and sufficient thermal stability for
vacuum deposition. As the excited state dynamics of this emitter class are different from most conventional OLED emitters and the pathway to maximum luminescence efficiency in thin films is not fully established, we study interactions between Eu(II) complexes and the host environment, based on density functional theory and time-resolved experiments. We identify steric shielding of the Eu(II) core and energetic confinement of the excited 5d electron, defined by molecular design as key factors governing efficient luminescence, providing a roadmap for rational design of Eu(II) emitters. Together, these results establish a basis for higher-efficiency and deeper blue OLEDs incorporating Eu(II) emitters.
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All authors Mahmoud Soleimani, Paulius Imbrasas, Jan-Michael Mewes, Felix Kaden, Stephanie Anna Buchholtz, Karl Leo, Sebastian Schellhammer, Carsten Rothe, Sebastian Reineke
Materials Science · Cross-listed from cond-mat.str-el
Topochemically-engineered coexistence of charge and spin orders in intercalated endotaxial heterostructures
Samra Husremović, Wanlin Zhang, Medha Dandu et al. (+10 more)
Correlated electron systems that host multiple electronic orders offer routes to multifunctional
quantum materials, but strong competition between these orders often prevents their coexistence. Here we show that nanoscale, metastable intercalated
heterostructures can stabilize a rare combination of long-range magnetism and a commensurate charge density wave (C-CDW) order in a single material. We synthesize a two-dimensional (2D) metastable
crystal, T/H-Fe$_x$TaS2, which comprises an endotaxial polytype
heterostructure of 1T-TaS$_2$ and H-TaS$_2$ with Fe intercalated in the van der Waals interfaces. In T/H-Fe$_x$TaS2, Fe intercalants provide localized
spins that support ferromagnetism, while 1T layers host a robust commensurate charge density wave (C-CDW) that persists to room temperature. In these intercalated
heterostructures, Fe content simultaneously tunes ordering of
spin and charge degrees of freedom, positioning topochemically-prepared intercalated endotaxial
heterostructures as a route to stabilize and control competing
quantum phases in 2D materials.
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All authors Samra Husremović, Wanlin Zhang, Medha Dandu, Berit H. Goodge, Isaac M. Craig, Ellis Kennedy, Matthew P. Erodici, Karen C. Bustillo, Chengyu Song, Jim Ciston, Sinéad Griffin, Archana Raja, D. Kwabena Bediako
Materials Science
Study of the Nonlinear Dependence of Anomalous Hall Conductivity on Magnetization in Weak Itinerant Ferromagnet ZrZn2
Surasree Sadhukhan, Stepan S. Tsirkin, Yaroslav Zhumagulov et al. (+1 more)
As opposed to the ordinary
Hall effect, the anomalous
Hall effect (AHE) remained unexplained for decades, and, amazingly, some misconceptions have survived even now, in particular, the claim that AHE is linearly related to the net magnetization. Karplus and Luttinger provided a
quantum-mechanical explanation of AHE by explicitly including the SOC and the Berry
curvature of electronic bands. They did address the question of linearity, but only in the relatively uncommon limit of the exchange coupling smaller than SOC. Now the linear relation in traditional ferromagnets is understood as a domain population effect: both AHE and magnetization are independently proportional to the domain disbalance. In this connection, it is interesting to check to what extent this relation will hold in single-domain itinerant ferromagnet, the closest case to that analyzed by Karplus and Luttinger? We answer this question by direct calculations, using the Karplus-Luttinger formula, of AHE in a prototypical itinerant ferromagnet, ZrZn$_2$. We show that in the zero-magnetization limit, $M\rightarrow 0$, the linear relation hold, but at rather small moments of $\sim 0.4\ \mu_B$/Zr breaks down completely and even flips the sign.
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All authors Surasree Sadhukhan, Stepan S. Tsirkin, Yaroslav Zhumagulov, Igor. I. Mazin
Materials Science · Cross-listed from physics.app-ph
High Breakdown Field Multi-kV UWBG AlGaN Transistors
Seungheon Shin, Kyle Liddy, Jon Pratt et al. (+6 more)
We demonstrate high-performance UWBG AlGaN PolFETs exhibiting a state-of-the-art combination of nearly 1 A/mm on-state current (~ 960 mA/mm) and large breakdown field (> 4.8 MV/cm) in high carrier density (1.15 x 1013 cm-2). Multi-kV robustness is successfully demonstrated exhibiting 1.28 and 2.17 kV by utilizing a gate-connected field plate structures in 3.9 and 6.8 {\mu}m LGD, corresponding to the extremely low specific on-resistance of 1.25 and 2.86 m{\Omega}cm2, respectively. High RF performance is also achieved, providing fT and fMAX, of 8.5 and 15 GHz, respectively, for 3.9 {\mu}m LGD. These results highlight UWBG AlGaN as a platform for both high-voltage RF and power applications.
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All authors Seungheon Shin, Kyle Liddy, Jon Pratt, Can Cao, Yinxuan Zhu, Brianna A. Klein, Andrew Armstrong, Andrew A. Allerman, Siddharth Rajan
Materials Science
Influence of Manganese Content on Plastic Deformation Mechanisms in Polycrystalline {\alpha}-Ti-Mn Alloys
G. Marković, M. Fedorov, M. Sokića et al. (+2 more)
Titanium
alloys are widely used in aerospace, biomedical, and energy applications owing to their high specific strength, corrosion resistance, and biocompatibility. Among them, $\alpha$-titanium
alloys with a hexagonal close-packed (hcp)
crystal structure exhibit characteristic deformation mechanisms governed by crystallographic slip and defect
evolution. In this study, the influence of manganese content on the plastic deformation mechanisms of polycrystalline $\alpha$-Ti-2Mn and $\alpha$-Ti-4Mn (at.%)
alloys is investigated using molecular dynamics simulations. Atomistic models were subjected to uniaxial loading at room temperature at a strain rate of 10$^9$ s$^{-1}$. The mechanical response was evaluated through stress-strain behavior, structural
evolution, dislocation nucleation and interaction, and analysis of the local deformation field. Plastic deformation in these $\alpha$-Ti-Mn
alloys is dominated by dislocation nucleation and their subsequent
evolution within the hcp
lattice. Increasing Mn content leads to higher stress levels and enhanced resistance to plastic deformation, accompanied by changes in dislocation activity and defect
evolution.
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All authors G. Marković, M. Fedorov, M. Sokića, K. Frydrych, F. J. Dominguez-Gutierrez
Materials Science
Grafted Low-Leakage Si/AlN p-n Diodes Enabled by Fluorinated AlN Interface
Yi Lu, Tsung-Han Tsai, Qingxiao Wang et al. (+19 more)
Ultrawide-bandgap AlN is a promising material for next-generation power electronics; however, its practical implementation is hindered by unstable surface chemistry and the high activation energy of p-type dopants. In particular, high-temperature rapid thermal annealing (RTA), required for forming low-resistance contacts on n-type AlN, leads to the formation of thick and defective surface
oxides that degrade heterojunction performance. In this work, we present an interface engineering approach based on fluorination-induced AlFx formation combined with SiNx passivation to suppress defect-assisted leakage in p-Si/n-AlN heterojunction diodes fabricated via
semiconductor grafting. A low-damage pseudo-atomic layer etching process is employed to remove RTA-induced
oxides and restore a near-stoichiometric AlN surface. Subsequent XeF2 treatment forms an ultrathin AlFx layer, which is stabilized by an atomic-layer-deposited SiNx capping layer prior to p-Si nanomembrane integration. Electrical measurements show that the engineered AlFx/SiNx interface reduces reverse leakage current by several orders of magnitude compared to untreated or
oxide-removed AlN surfaces, while preserving forward conduction characteristics. Temperature-dependent analysis indicates strong suppression of Poole-Frenkel emission and a shift of leakage onset to higher reverse bias, ultimately limited by bulk AlN
crystal quality. X-ray photoelectron spectroscopy and transmission electron microscopy confirm the formation of Al-F bonds, reduced Al-O content, and the presence of a thin interfacial SiOx/SiON layer. These results establish AlFx/SiNx passivation as an effective strategy for stabilizing AlN interfaces and enabling low-leakage ultrawide-bandgap heterojunction devices.
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All authors Yi Lu, Tsung-Han Tsai, Qingxiao Wang, Haicheng Cao, Jie Zhou, You Jin Koo, Chenyu Wang, Yang Liu, Yueyue Hao, Michael Eller, Connor Bailey, Stephanie Liu, Nicholas J. Tanen, Zhiyuan Liu, Mingtao Nong, Robert M. Jacobberger, Tien Khee Ng, Katherine Fountaine, Vincent Gambin, Boon S. Ooi, Xiaohang Li, Zhenqiang Ma
Materials Science · Cross-listed from cond-mat.mes-hall
Tunable Valley Polarization in Diamond
Nattakarn Suntornwipat, Jan Isberg and Saman Majdi
Device stability is essential for
quantum information technologies, where reliable control of electronic states is crucial. Diamond valleytronics offers a promising platform by exploiting the valley degree of freedom to store and manipulate information. In this work, we demonstrate a diamond-based valley transistor with a dual-gate, two-drain architecture that enables tunable valley-polarized transport via gate voltage modulation. By leveraging the significant effective-mass anisotropy of diamond's conduction band valleys, this architecture provides control over spatial distribution and transit times. We further demonstrate that valley-polarized transport in diamond is remarkably robust against thermal variations over macroscopic distances. These results demonstrate the resilience of valley states and highlight diamond's potential for energy-efficient valleytronic devices in next-generation
quantum and high-power electronics.
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Materials Science
Optoelectronic and Thermoelectric Properties of High-Performance AlSb Semiconductors
Dilshod Nematov, Amondulloi Burkhonzoda, Iskandar Raufov et al. (+6 more)
This study presents a comprehensive first-principles investigation of the optoelectronic and thermoelectric properties of aluminum antimonide (AlSb) in its cubic (F-43m) and hexagonal (P63mc) phases. Structural optimization was performed using the SCAN functional, and all electronic and optical properties were evaluated using the modified Becke-Johnson potential combined with the Hubbard correction (mBJ+U), which best describes the band-edge electronic structure, explicitly accounting for the contribution of the d-states of the Sb half-core, which cannot be adequately accounted for by conventional functionals and may be overestimated by hybrid approaches. Both AlSb phases are found to be quasi-direct bandgap
semiconductors, with calculated band gaps of 1.71 eV for the cubic phase and 1.50 eV for the hexagonal phase, in good agreement with available experimental data. The optical response reveals strong absorption in the visible and ultraviolet regions, moderate reflectivity, and high refractive indices, indicating pronounced light-matter interaction characteristic of III-V
semiconductors. The hexagonal phase exhibits enhanced low-energy optical absorption due to its reduced
symmetry and narrower band gap. Thermoelectric analysis demonstrates large negative Seebeck coefficients, thermally activated carrier generation, and a monotonic increase of the power factor with carrier concentration for both phases. The cubic phase shows higher power factor values due to enhanced carrier mobility, whereas the hexagonal phase benefits from reduced thermal conductivity, which is favorable for thermoelectric performance at elevated temperatures. These results establish AlSb as a multifunctional
semiconductor with tunable optoelectronic and thermoelectric properties and highlight the importance of an accurate treatment of Sb d-electron effects for reliable property prediction.
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All authors Dilshod Nematov, Amondulloi Burkhonzoda, Iskandar Raufov, Sherali Murodzoda, Saidjafar Murodzoda, Sakhidod Sattorzoda, Anushervon Ashurov, Makhsud Barot Islomzoda, Kholmirzo Kholmurodov
Materials Science
Key Role of Charge Disproportionation in Monoclinic Semiconducting Fe$_2$PO$_5$, a Room-Temperature d-Wave Altermagnet Candidate
Zhen Zhang, Mohd Anas, Andrey Kutepov et al. (+2 more)
$\beta$-Fe$_2$PO$_5$ is an emerging room-temperature d-wave altermagnet featuring quasi-one-dimensional
crystal and
magnetic structures, orthogonal transport channels for opposite
spins, and large band
spin splitting, which is a promising material for next-generation spintronics and magnonics. However, its
crystal and electronic structures remain inconclusive. Here, joint experimental and theoretical studies confirm and explain the appearance of its monoclinic structure and semiconducting band gap. We discover that an electronic instability appears in the tetragonal metallic state as the joint effect of density functional theory and Hubbard U correction (DFT+U) and results in a charge disproportionation, which in turn stabilizes the monoclinic distortion with narrow gap formation. The successful capture of this effect within DFT+U requires accounting for the relevant
symmetry-breaking energy-lowering channels – charge disproportionation and structural distortion; otherwise, tetragonal-
symmetry-constrained calculations yield only a metallic state. Fe$_2$PO$_5$ is thus best described as a correlation- and hybridization-assisted, distortion-coupled, charge-disproportionated
semiconductor. It represents a rare room-temperature semiconducting d-wave altermagnet. It also provides a rare platform for studying the coexistence of altermagnetism and charge density wave in quasi-one-dimensional systems.
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All authors Zhen Zhang, Mohd Anas, Andrey Kutepov, Parashu Kharel, Vladimir Antropov
Materials Science
Ultrafast nonlinear Hall effect in black phosphorus
Maciej Dendzik, Andrea Marini, Samuel Beaulieu et al. (+9 more)
The nonlinear
Hall effect (NHE) is a recently discovered member of the
Hall effect family in which the
Hall voltage shows a nonlinear behavior when a transverse electric field is applied. While the NHE does not require broken time-reversal
symmetry, such as that induced by a
magnetic field, it requires broken inversion
symmetry, which limits the range of suitable systems and potential applications. Here, we demonstrate an ultrafast NHE in centrosymmetric black phosphorus through dynamical
symmetry breaking using femtosecond light pulses. We provide a detailed microscopic picture of excited carrier dynamics and induced fields using momentum-resolved photoemission spectroscopy combined with ab-initio calculations. The ultrafast NHE is observed exclusively for the light polarization aligned with the armchair high-
symmetry direction and persists over 300 fs, which opens new possibilities for selective and ultrafast light-to-current conversions.
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All authors Maciej Dendzik, Andrea Marini, Samuel Beaulieu, Shuo Dong, Tommaso Pincelli, Julian Maklar, R. Patrick Xian, Enrico Perfetto, Martin Wolf, Gianluca Stefanucci, Ralph Ernstorfer, Laurenz Rettig
Materials Science
The HTC-Claw: Automating Discovery through High-Throughput Computational Campaigns
Lianduan Zeng, Xiao Zhou, Xueru Zheng et al. (+6 more)
With the advancement of the Materials Genome Initiative, high-throughput computation has become central to accelerating materials discovery. However, conventional first-principles workflows are cumbersome and error-prone. Existing high-throughput tools, while efficient at batch job submission, lack intelligence: they cannot automatically plan tasks based on scientific objectives or dynamically adapt workflows according to intermediate results. To address these limitations, this paper proposes and implements HTC-Claw, an intelligent high-throughput computational platform built upon the OpenClaw framework. The key innovations of HTC-Claw are: 1) An
agent-based framework for automatic decomposition of high-level research goals into parallelizable task sets; 2) A closed-loop execution engine that integrates real-time analysis and reporting; 3) Adaptive decision-making and workflow iteration capabilities based on intermediate results; and 4) A decoupled, modular architecture that separates the scheduling system from functional modules, enhancing extensibility and robustness. Case studies demonstrate that HTC-Claw enables an intelligent, end-to-end workflow from user intent to final reporting in materials exploration
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All authors Lianduan Zeng, Xiao Zhou, Xueru Zheng, Ning Gao, Lei Liu, Yunxuan Cao, Hongjian Chen, Zhongyang Wang, Tongxiang Fan
Materials Science
Large Language Model Assisted Discovery of Optimal Dopants for Enhanced Thermoelectric Performance in CoSb$_3$ Based Skutterudites
Yagnik Bandyopadhyay, Dylan Noel Serrao and Houlong L. Zhuang
We present a data-driven approach for accelerating the discovery of high-performance CoSb$_3$-based skutterudites by curating a comprehensive
dataset of compositions with various filler elements from over 300 research articles. Leveraging large
language models (LLMs), we extract and embed compositional representations, which are then used to train a regression head for predicting thermoelectric figure of merit. Compared to traditional deep neural networks relying on elemental descriptors such as atomic radii, our LLM-based model achieves significantly lower mean-squared error losses. We further employ the trained model to propose novel filler compositions with promising thermoelectric properties. Finally, we support these predicted candidates through density functional theory and molecular dynamics calculations to assess their electrical and thermal conductivity. This data-driven approach demonstrates the potential of combining natural
language processing, machine learning, and
quantum simulations for thermoelectric materials design.
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Materials Science · Cross-listed from physics.chem-ph
The BOS-Lig Dataset: Accurate Ligand Charges from a Consensus Approach for 66,810 Experimentally Synthesized Ligands
Roland G. St. Michel, Ryan J. Jang, Aaron G. Garrison et al. (+2 more)
Understanding ligand properties is essential for computational high-throughput screening of transition metal complexes. However, ligand properties such as net charge and other information such as their application area are often absent or inconsistently recorded in crystallographic
datasets. Here, we construct a ligand
dataset from 126,985 mononuclear transition metal complexes curated from the Cambridge Structural Database. Using an iterative charge-balancing workflow that combines complex charges, metal oxidation states, and consensus across crystallographic observations, we confidently assign net charges to 66,810 ligands among 94,581 identified unique ligand structures to curate the Boston Open-Shell Ligand (BOS-Lig)
dataset. The workflow assigns ligand charges in homoleptic complexes first and then iteratively propagates these assignments across heteroleptic environments, allowing charges to be inferred even when direct charge information is unavailable. We analyze cases where simple heuristics such as the octet rule would have failed and introduce a purity metric to identify when our charge assignments may be incorrect. Each ligand is also classified in terms of its metal coordinating atoms and whether there are multiple variants (i.e., hemilability). We then link complexes to their associated journal abstracts and apply a topic-modeling workflow to link 25,146 ligands with functional application areas spanning reactivity, redox chemistry, biological chemistry, and photophysical chemistry. Together, we provide an experimentally grounded
dataset of ligand chemical space that connects charge and functional application as a foundation for computational screening and data-driven ligand design.
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All authors Roland G. St. Michel, Ryan J. Jang, Aaron G. Garrison, Ilia Kevlishvili, Heather J. Kulik
Materials Science
RIXS Identification of Optical Phonon-Spin Coupling Effects in CrSBr
Jayajeewana N. Ranhili, Chamini S. Pathiraja, Brody Brogdon et al. (+10 more)
Resonant inelastic x-ray scattering provides experimental signatures of
spin-
phonon coupling in CrSBr through temperature-dependent Cr $L$-edge spectra. Low-energy excitations are observed exclusively in the low-temperature
antiferromagnetic phase as energy-loss features. A quasi-elastic peak at approximately 42 meV is observed under $\pi$-polarization. Density functional theory
phonon-mode calculations identify these RIXS features as occurring within the same energy range as bond-bending optical
phonon modes associated with distortions of the Cr–S–Cr network. The pronounced suppression of these low-energy excitations upon warming into the paramagnetic phase, together with their polarization dependence, the calculated
phonon spectrum, and a
spin-renormalized electron-
phonon RIXS framework, indicates a strong interplay between
magnetic correlations and
lattice dynamics. While the loss features appear at energies characteristic of optical
phonons, the significant overlap of the optical-
phonon and
magnon bands suggests that the temperature-dependent behavior should not be regarded as purely
lattice-derived excitations. Instead, the room-temperature suppression of the low-energy RIXS peaks is explained in terms of a
spin-
phonon coupling effect on the $L$-edge electron-
phonon RIXS mechanism. The interpretation is supported by the combined experimental observations,
phonon calculations, and theoretical modeling, rather than by temperature contrast alone. These results support
spin-
phonon coupling as a plausible and consistent interpretation of the observed temperature-dependent RIXS response and demonstrate that
magnetic order can strongly influence
phonon-related spectral weight in the RIXS spectrum.
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All authors Jayajeewana N. Ranhili, Chamini S. Pathiraja, Brody Brogdon, John Cenker, Xiaodong Xu, Daniel Chica, Xavier Roy, Stefano Agrestini, Mirian Garcia-Fernandez, Ke-Jin Zhou, Yi-De Chuang, Trinanjan Datta, Byron Freelon
Materials Science
Composition design of refractory compositionally complex alloys using machine learning models
Tao Liang, Eric A. Lass, Haochen Zhu et al. (+5 more)
Refractory compositionally complex
alloys (RCCAs) are considered the next generation high-temperature materials. However, their high-dimensional composition spaces are too large to explore by traditional density functional theory or experimental means, making new RCCA discovery slow and cumbersome. This work has addressed these challenges with an integrated composition design framework that can efficiently and exhaustively explore the relationship between the compositions and two fundamental aspects: 1) the phase stability, including the target body-centered cubic (BCC) phase and its competing phases (hexagonal closed-pack (HCP) structures, Laves and B2 intermetallic phases), and 2) the mechanical properties. This framework is demonstrated with RCCAs within nine refractory metals (Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). Theory-guided machine learning (ML) models were employed to find the composition-mechanical property relationship of RCCAs, where the established theory is used to supplement the yield strength data at ultra-high temperature, and a forward sequential feature selection (SFS) is used to determine feature selection. The resulting ML model for temperature-dependent yield strength was found to have an R_squared value of 0.98 over the entire temperature range (from 0 to 2000 K). The impact of each constituent element on the six key properties is evaluated. The addition of Nb tends to stabilize the BCC phase and the addition of Ti improves the ductility of RCCAs. Combined with all methods involved in this framework, the on-demand designer allows the
alloy designers to have all properties for any RCCA compositions and narrow down the composition space by applying custom screening criteria. The output from the predictor and screener provides valuable guidance for our experimental study of RCCAs and accelerates the pace of materials discovery.
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All authors Tao Liang, Eric A. Lass, Haochen Zhu, Carla Joyce C. Nocheseda, Philip D. Rack, Stephen Puplampu, Dayakar Penumadu, Haixuan Xu
Materials Science
Lattice location of ion-implanted 6He in diamond
U. Wahl, J.G. Correia, A. Costa et al. (+7 more)
The properties of He in diamond are of interest with respect to geological dating and the creation of color centers with possible
quantum applications. We report on the
lattice location of the short-lived ion implanted
nuclear probe 6He (t1/2=807 ms) in diamond, which was performed using the beta emission channeling method at CERN's ISOLDE facility. 6He was implanted with 30 keV into a single-crystalline artificial diamond sample kept at a temperature ranging from 30 deg C up to 800 deg C. By means of comparing the measured emission channeling patterns along different crystallographic directions with simulated yields for a variety of possible sites, we conclude that the implanted 6He occupies tetrahedral (T) interstitial sites, in agreement with theoretical predictions that T sites should be the preferred position of He in diamond. Implantation at 800 deg C resulted in a drop in the tetrahedral interstitial fraction by 20%, which we interpret as the onset of
diffusion, 6He thus being able to change to
lattice sites of low crystallographic
symmetry, or reach the surface of the sample or escape to the bulk during its lifetime. We estimate the activation energy for interstitial migration of He to be around 1.63-2.89 eV, which agrees with theoretical predictions of 1.41-2.36 eV from the literature. Activation energies around 2 eV would mean that simple interstitial He cannot be stable in diamond on geological time scales, thus to remain inside, it should be bound to some defect in the material or exist in another form such as within inclusions of other minerals or
liquids, or possibly small He bubbles.
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All authors U. Wahl, J.G. Correia, A. Costa, B. Biesmans, G. Magchiels, S.M. Tunhuma, A. Lamelas, A. Vantomme, L.M.C. Pereira, the ISOLDE Collaboration
Materials Science · Cross-listed from physics.chem-ph
Reference Energies for Non-Relativistic Core Ionization Potentials
Antoine Marie, Loris Burth and Pierre-François Loos
Deep-lying core electrons carry highly localized, site-specific information that forms the basis of X-ray photoelectron spectroscopy. Accurately predicting their associated core ionization potentials (IPs) is a demanding theoretical task, requiring a balanced treatment of strong orbital relaxation, electron correlation, and relativistic effects. Over the years, a variety of approaches have been developed, ranging from state-specific wave function methods to linear-response formalisms and Green's function techniques. However, their assessment has often relied on comparisons with experiment, where multiple sources of error (basis set incompleteness, relativistic corrections, and vibrational effects) are entangled, making it difficult to isolate the performance of correlation treatments. In the present work, we establish a consistent, theory-based
benchmark for core IPs by computing 84 non-relativistic values (73 second-row and 11 third-row IPs) at the full configuration interaction level within the core-valence separation approximation, using large correlation-consistent basis sets augmented with tight-core and diffuse functions (aug-cc-pCVXZ). These results define theoretical best estimates within a fixed finite basis set, providing a chemically accurate reference for method development and validation. Importantly, our
dataset allows for systematic, theory-versus-theory comparisons that disentangle correlation and relaxation effects from other physical contributions. On this basis, we assess the performance of widely used approximate methods, including equation-of-motion coupled-cluster approaches up to the inclusion of quadruple excitations, the one-shot $G_0W_0$ scheme, as well as state-specific methods.
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Materials Science
ALD Zinc Tin Oxide Buffers for Chalcopyrite Solar Cells: Electrical Barriers and Conduction Band Cliffs
Boaz Koren, Francesco Lodola, Zhuangyi Zhou et al. (+5 more)
Sulfide chalcopyrite, Cu(In,Ga)S2, having wide bandgap (larger than 1.5 eV), favorable optoelectronic properties, and high stability, is a promising top-
cell absorber for tandem applications. Adapting device structures optimized for 1.0 - 1.2 eV absorbers to wide bandgap absorbers requires modification of the buffer layer. This work investigates atomic layer deposition of ZnSnO as an alternative buffer layer to conventional CdS. A critical parameter for bufferperformance is the conduction band offsets on both sides of the buffer. To investigate these buffers we electrically characterize
solar cells utilizing different compositions of ZnSnO. The Sn/(Sn+Zn) atomic ratio is controlled by the ratio of ZnO to SnO cycles during atomic layer deposition.
Solar cells were fabricated utilizing CuInSe2, Cu(In,Ga)Se2, and Cu(In,Ga)S2 absorbers, allowing cross-comparison with a variety of conduction band minimum energies. Buffer variation has two primary effects on
cell performance: 1. Low tin buffers decrease the activation energy of interface recombination, reducing open
circuit voltage. These observations indicates a cliff, a decrease of the conduction band minimum from absorber to buffer. 2. High tin buffers reduce the fill factor for all measured
cells, and reduce the short
circuit current under certain conditions. This observation indicates an electron transport barrier, conduction band offsets which limit the transport of electrons across the buffer, in either direction. We conclude that tin content correlates positively with the conduction band minimum of these buffers. Comparing different absorbers, cliffs occurs at lower Sn contents and the effects of barriers are more dramatic for absorbers with lower conduction band minima.
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All authors Boaz Koren, Francesco Lodola, Zhuangyi Zhou, Trong Tien Le, Kulwinder Kaur, Simon Backes, Michele Melchiorre, Susanne Siebentritt
Materials Science
Additive-Induced Stabilization of the Energetic Landscape of PM6:Y12 Organic Solar Cells
Bekcy Joseph, Shivam Singh, Nathaniel P. Gallop et al. (+7 more)
Solvent additive engineering is a common strategy in organic photovoltaic (OPV) fabrication to improve film morphology and enhance device performance by controlling phase-separation kinetics and crystallinity. However, its effect on photostability, particularly with respect to the
evolution of the energetic landscape under operational stress, remains unclear. This study investigates the impact of the additive 1-chloronaphthalene (1-CN) on the
evolution of the device's energetic landscape in PM6:Y12 bulk heterojunction organic
solar cells upon photoaging. Ultraviolet photoemission spectroscopy combined with argon gas cluster ion beam depth profiling is employed to probe the depth-resolved
evolution of donor (PM6) and acceptor (Y12) energy levels before and after photodegradation. Our findings show that in additive-free devices, photodegradation leads to a significant 200 meV downward shift in the PM6 highest occupied molecular orbital (HOMO) level, reducing the donor-acceptor HOMO offset and impairing the driving force for hole transfer. As a consequence, the device experiences substantial efficiency loss. On the other hand, the incorporation of 1-CN effectively stabilizes the PM6 HOMO level, preserving adequate driving force for efficient
exciton dissociation. Advanced X-ray diffraction characterization reveals more pronounced nanostructural degradation in blends without 1-CN than those with 1-CN upon photoaging. Collectively, these findings identify PM6 as the primary degradation pathway in PM6:Y12 blends and demonstrate that 1-CN enhances device stability by stabilizing PM6 energetics and preserving the nanostructural integrity upon photoaging.
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All authors Bekcy Joseph, Shivam Singh, Nathaniel P. Gallop, Fabian Eller, Alexander Ehm, Julius Brunner, Dietrich R. T. Zahn, Eva Herzig, Boris Rivkin, Yana Vaynzof
Materials Science
Loss analysis of Low Bandgap (Ag,Cu)(In,Ga)Se2 Solar Cells for Tandem Applications
Francesco Lodola, Sevan Gharabeiki, Maximilian Krause et al. (+3 more)
Tandem
solar cells can better harness the energy of the
solar spectrum. Chalcopyrite
solar cells have drawn
attention, being the only highly efficient devices with bandgap around 1.0 eV, suitable for bottom
cells. In the quest for better efficiencies, we conduct a complete loss analysis of 1.0 eV bandgap (Ag,Cu)(In,Ga)Se2
cells with efficiencies around 18.5%. We perform absolute photoluminescence, electroluminescence, JV and EQE measurements on the absorber and the finished
cells to analyze losses of short-
circuit current, open-
circuit voltage and fill factor. The relevant losses in current are due to absorption losses in the absorber and could only be mitigated by light management structures. But the most significant losses are found in the voltage, due to non-radiative recombination in the absorber, and the fill factor, due to a high diode factor. The diode factor of the
cells is significantly higher than in the absorber alone, indicating a strong influence of recombination in the space charge region.
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All authors Francesco Lodola, Sevan Gharabeiki, Maximilian Krause, Shiro Nishiwaki, Romain Carron, Susanne Siebentritt
Materials Science
Near 13% efficient semitransparent Cu(In,Ga)S2 solar cells with band gap of 1.6 eV on transparent back contact
Kulwinder Kaur, Arivazhagan Valluvar Oli, Michele Melchiorre et al. (+4 more)
Wide-gap Cu(In,Ga)S2
solar cells with In2O3:Sn (ITO) as transparent back contact are evaluated for the application as top
cells in tandem devices. The effect of Na on the
solar cell performance is investigated by supplying additional Na by NaF co-evaporation or exclusively by Na
diffusion from glass. An efficiency of 12.7% is achieved for a semitransparent
solar cell with a band gap of 1.6 eV, with sufficient Na
diffusion from glass only, allowed by a thin ITO layer. Absorber grown with additional NaF co-evaporation during Cu(In,Ga)S2 growth on thicker ITO show a comparable efficiency of 12%. High temperature growth at Tsub = 630{\deg}C enhances overall absorber quality and results in wide-gap absorbers, with photoluminescence
quantum yield improved to 1.5 x 10-5, two orders of magnitude higher than absorber grown at low temperature. NaF co-evaporation is effective in suppressing deep defects, thereby reducing non-radiative recombination and enhancing photoluminescence
quantum yield further. A GaOx interfacial layer is formed at the rear contact, likely contributing to the passivation of the back contact. With the presence of thick GaOx layer, current blocking effects are visible in the current-voltage curves. On the contrary, a thinner ITO tends to result in thinner GaOx layer and no current blocking is observed.
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All authors Kulwinder Kaur, Arivazhagan Valluvar Oli, Michele Melchiorre, Wolfram Hempel, Wolfram Witte, Jan Keller, Susanne Siebentritt