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Site-decorated model for unconventional frustrated magnets: Ultranarrow phase crossover and two-dimensional spin reversal transition
Here, the site-decorated Ising model is introduced to advance the understanding and experimental realization of the recently discovered one-dimensional (1D) finite-temperature ultranarrow phase crossover in an external magnetic field, while mitigating the geometric complexities of traditional bond-decorated models. The unconventional frustration and physics are clarified by exactly mapping the 1D site-decorated Ising model in a magnetic field onto a zero-field bond-decorated 𝐽 1 −𝐽 2 Ising model with conventional geometrical frustration. Furthermore, although higher-dimensional Ising models in an external field remain unsolved exactly, an exact solution for a spin-reversal transition—driven by an exotic, hidden half-ice, half-fire state induced by site decoration—is derived. This transition, triggered by a slight variation in temperature or magnetic field—without changing its direction—even in the weak-field limit, offers a promising route toward energy-efficient applications such as data storage and processing. The results suggest that site decoration offers an avenue for materials and device design, particularly in systems such as mixed 𝑑−𝑓 compounds, optical lattices, and neural networks, calling for further studies with site-decorated Heisenberg models. In addition, the site-decorated model offers a rigorous test ground for artificial intelligence (AI) in science, as the analytic derivation of the present results was not only validated but also improved by a general-purpose large language model, inspiring the use of AI as scientific discoverer.
Enhanced flexibility and thermal conductivity of HfC decorated carbon nanofiber mats
Future-generation spacecraft components allude discovery of novel materials that can withstand extreme environments (>2000 °C). The combined effect of ultra-high temperature ceramics (UHTCs) and carbon fibers (C f ) can satisfy the demanding requirements of aerospace applications. A novel, hybrid, and flexible hafnium carbide (HfC)-decorated carbon nanofiber (C nf ) mat was fabricated via electrospinning. Enhanced thermal stability of the flexible HfC decorated C nf over C nf can be elucidated from the 20-fold increment in thermal conductivity and the onset of degradation at higher temperatures (840 °C). Successful integration of multi-layered sandwich lattice using in-housed fabricated HfC decorated C nf showed retention of the fibrous structure even after extreme spark plasma sintering (SPS) process at 1850 °C. Fabricating a similar multi-layered structure using procured C f was unsuccessful due to bundled agglomeration and micron-sized fibers. High-load indentation suggests that HfC decorated C nf interlayer is stronger (~2.3 times) than the parent UHTC with no cracking at the interface. Compared with the HfC matrix, the indentation-damaged area at the interface reduced up to ~56% due to toughening mechanisms such as C nf , fiber pull-out and bridging. The synthesized HfC decorated Cnf mat is proposed as an ultra-thin filler material for joining similar or dissimilar UHTCs while maintaining similar chemistry and better mechanical integrity at the interface. Furthermore, the findings insinuate a new paradigm in designing hybrid and flexible ceramic-containing materials for thermal protection systems (TPS) of future-generation spacecraft components that can mitigate failure in extreme environments (>2000 °C).
Effective optimization of atomic decoration in giant and superstructurally ordered crystals with machine learning
Crystals with complicated geometry are often observed with mixed chemical occupancy among Wyckoff sites, presenting a unique challenge for accurate atomic modeling. Similar systems possessing exact occupancy on all the sites can exhibit superstructural ordering, dramatically inflating the unit cell size. In this work, a crystal graph convolutional neural network (CGCNN) is used to predict optimal atomic decorations on fixed crystalline geometries. This is achieved with a site permutation search (SPS) optimization algorithm based on Monte Carlo moves combined with simulated annealing and basin-hopping techniques. Our approach relies on the evidence that, for a given chemical composition, a CGCNN estimates the correct energetic ordering of different atomic decorations, as predicted by electronic structure calculations. This provides a suitable energy landscape that can be optimized according to site occupation, allowing the prediction of chemical decoration in crystals exhibiting mixed or disordered occupancy, or superstructural ordering. Verification of the procedure is carried out on several known compounds, including the superstructurally ordered clathrate compound Rb8Ga27Sb16 and vacancy-ordered perovskite Cs2SnI6, neither of which was previously seen during the neural network training. In addition, the critical temperature of an order–disorder phase transition in solid solution CuZn is probed with our SPS routines by sampling site configuration trajectories in the canonical ensemble. This strategy provides an accurate method for determining favorable decoration in complex crystals and analyzing site occupation at unprecedented speed and scale.
Controlling the Ru Island Decoration on Ni Nanoparticles to Tune the Activity for 5-Hydroxylmethylfurfural (HMF) Oxidation
Controlling the island decoration on metal nanoparticle supports is a major opportunity for improving the catalytic activity and an attractive synthetic challenge. The structure of the decorating metal determines how it interacts with the metal support and how it effectively catalyzes the reactants and the intermediates. In this work, we demonstrate that a slow-growth method maximizes the formation of Ru islands on faceted, branched Ni nanoparticles, thereby controlling the number of Ru–Ni atomic interactions and improving the catalytic activity. The Ru islands on branched Ni nanoparticles with the highest loading of Ru (9%) exhibited the highest activity for the electro-oxidation of biomass-derived 5-hydroxymethylfurfural (HMF). In conclusion, these results demonstrate the ability to synthetically control the second metal decoration to tune metal–support interactions, thereby enhancing the catalytic activity.
Single-particle detection of enhanced polarizability in Au-decorated semiconducting nanorods via scanning dielectric microscopy
Hybrid nanostructures that combine semiconducting and metallic components offer great potential for photothermal therapy, optoelectronics, and sensing, by integrating tunable optical properties with enhanced light absorption and charge transport. Boosting the integrated performance of these hybrid systems demands techniques capable of probing local variations of the physical properties inaccessible to bulk analysis. Here, we report the single-particle dielectric characterization of hybrid, semiconducting bismuth sulfide (Bi 2 S 3 ) nanorods (NR) decorated with metallic Au nanoparticles (NP), employing scanning dielectric microscopy, which uses electrostatic force microscopy in combination with finite-element numerical simulations. We reveal a pronounced enhancement in the local dielectric response of Bi2S3 upon Au decoration, attributed to interfacial polarization and electron transfer from Au to the Bi 2 S 3 matrix, thus suggesting a enhanced metallic-like polarizability at the single-particle level. Numerical simulations show that the response is dominated by the vertical component of the permittivity and that the decorating metallic Au NP produce only moderate shielding of the semiconductor Bi 2 S 3 NR core, indicating that the large increase in the dielectric response originates primarily from intrinsic modifications within the NR. Overall, these findings provide direct insight into structure–property relationships at the single-particle level, supporting the rational design of advanced hybrid nanostructures with tailored electronic functionalities.
Unraveling H2 chemisorption and physisorption on metal decorated graphene using quantum Monte Carlo
Molecular hydrogen has the potential to significantly reduce the use of carbon dioxide emitting energy processes. However, hydrogen gas storage is a major bottleneck for its large-scale use as current storage methods are energy intensive. Among different storage methods, physisorbing molecular hydrogen at ambient pressure and temperatures is a promising alternative—particularly in light of the advancements in tunable lightweight nanomaterials and high throughput screening methods. Nonetheless, understanding hydrogen adsorption in well-defined nanomaterials remains experimentally challenging and reference information is scarce despite the proliferation of works predicting hydrogen adsorption. We focus on Li, Na, Ca, and K, decorated graphene sheets as substrates for molecular hydrogen adsorption, and compute the most accurate adsorption energies available to date using quantum diffusion Monte Carlo (DMC). Building on our previous insights at the density functional theory (DFT) level, we find that a weak covalent chemisorption of molecular hydrogen, known as Kubas interaction, is feasible on Ca decorated graphene according to DMC, in agreement with DFT. This finding is in contrast to previous DMC predictions of the 4H2/Ca+ gas cluster (without graphene) where chemisorption is not favored. However, we find that the adsorption energy of hydrogen on metal decorated graphene according to a widely used DFT method is not fully consistent with DMC. The reference adsorption energies reported herein can be used to find better work-horse methods for application in large-scale modeling of hydrogen adsorption. Furthermore, the implications of this work affect strategies for finding suitable hydrogen storage materials and high-throughput methods.
Half-ice, half-fire-driven ultranarrow phase crossover in one-dimensional decorated 𝑞-state Potts ferrimagnets: An AI-co-led exploration
OpenAI’s reasoning model o3-mini-high was used to carry out an exact analytic study of one-dimensional ferrimagnetic site- and bond-decorated 𝑞-state Potts models. We demonstrate that the finite-temperature ultranarrow phase crossover (UNPC), driven by a hidden “half-ice, half-fire” state recently discovered in the 𝑞=2 case (Ising model), persists for 𝑞>2. Moreover, we identify unique features for 𝑞>2, including the dome structure in the field-temperature phase diagram, and for large 𝑞 a secondary high-temperature UNPC to the fully disordered paramagnetic state. As the UNPC quickly approaches a genuine transition by enhancing 𝐽, the interaction between the backbone spins, two distinct behaviors emerge: In the site-decorated Potts model, 𝑇 0 is independent of 𝐽 and thus remains unchanged (Type-I UNPC), and in the bond-decorated Potts model with 𝑞>2, 𝑇 0 depends on 𝐽 and quickly shifts toward a finite temperature as 𝐽 increases (Type-II UNPC). These results establish a versatile framework for engineering controlled fast state-flipping switches in low-dimensional systems. Our nine-dan artificial intelligence (AI)-contribution framework assigns AI the meritorious status of AI-co-led discovery in this work.
Mechanisms of adsorbing hydrogen gas on metal decorated graphene
Hydrogen is a key player in global strategies to reduce greenhouse gas emissions. In order to make hydrogen a widely used fuel, we require more efficient methods of storing it than the current standard of pressurized cylinders. An alternative method is to adsorb H 2 in a material and avoid the use of high pressures. Among many potential materials, layered materials such as graphene present a practical advantage as they are lightweight. However, graphene and other 2D materials typically bind H 2 too weakly to store it at the typical operating conditions of a hydrogen fuel cell, meaning that high pressure would still be required. Modifying the material, for example by decorating graphene with adatoms, can strengthen the adsorption energy of H 2 molecules, but the underlying mechanisms are still not well understood. In this work, we systematically screen alkali and alkaline-earth metal decorated graphene sheets for the static thermodynamic adsorption of hydrogen gas from first principles and focus on the mechanisms of binding. We show that there are three mechanisms of adsorption on metal decorated graphene and each leads to distinctly different hydrogen adsorption structures. The three mechanisms can be described as weak van der Waals physisorption, metal adatom facilitated polarization, and Kubas adsorption. Among these mechanisms, we find that Kubas adsorption is easily perturbed by an external electric field, providing a way to tune H 2 adsorption. In conclusion, this work is foundational and builds our understanding of H 2 adsorption under idealized conditions.
A Structure-Preserving Decorated Particle Method for the Vlasov-Poisson System
We revisit the Scovel-Weinstein framework (Scovel & Weinstein, CPAM 1994) for reducing the Vlasov-Poisson system while preserving its Hamiltonian structure. Standard particle-in-cell (PIC) algorithms approximate the distribution function by macro-particles with position and velocity. In contrast, Scovel-Weinstein decorated particles involve additional shape degrees of freedom, while maintaining a finite-dimensional reduction with Hamiltonian structure inherited from the continuum model. Although the original work established this structure three decades ago, its computational potential has remained largely unexplored. We present a practical implementation of the Scovel-Weinstein model and compare it with a standard PIC algorithm. Numerical experiments demonstrate that macro-particles in standard PIC can be replaced by far fewer decorated particles while retaining comparable accuracy. This decorated particle approach offers a new structure-preserving paradigm for kinetic plasma simulation.
Synthesis of Metal Nanoparticle-decorated Carbon Nanotubes under Ambient Conditions
This viewgraph presentation reviews the production of Metal Nanoparticle-decorated carbon Nanotubes. Multi-walled carbon nanotubes (MWCNTs) were efficiently decorated with metal nanoparticles (e.g. Ag, Pt, etc.) using the corresponding metal acetate in a simple mixing process without the need of chemical reagents or further processing. The conversion of acetate compounds to the corresponding metal reached over 90%, forming nanoparticles with average diameters less than 10 nm under certain conditions. The process was readily scalable allowing for the convenient preparation of multi-gram quantities of metal nanoparticle-decorated MWCNTs in a matter of a few minutes. These materials are under evaluation for a variety of electrical and catalytic applications. The preparation and characterization of these materials will be presented. The microscopic views of the processed MWCNTs are shown
Decorated TQFTs and their Hilbert spaces
We discuss topological quantum field theories that compute topological invariants which depend on additional structures (or decorations) on three-manifolds. The q-series invariant $\hat{Z}$(q) proposed by Gukov, Pei, Putrov, and Vafa is an example of such an invariant. We describe how to obtain these decorated invariants by cutting and gluing and make a proposal for Hilbert spaces that are assigned to two-dimensional surfaces in the $\hat{Z}$-TQFT.
Solvent-free synthesis of Co single atom and nanocluster decorated N-doped carbon for efficient oxygen reduction
The advancement of efficient, cheap, and durable catalysts for oxygen reduction reaction (ORR) to substitute Pt/C in metal-air batteries is of paramount importance. However, traditional solvent-based methods fall short in terms of environmental benign and scalability. Herein, a solvent-free organic-inorganic self-assembly approach is explored to construct cobalt single atom and cobalt nanocluster decorated nitrogen-doped porous carbon spheres (Co-SA/NC@NCS). The solvent-free synthesis demonstrates an impressively high yield (282 g/L) and the resultant Co-SA/NC@NCS possesses a high N content (6.9 wt%). Density functional theory calculations disclose that the Co-SAs and Co-NCs are able to optimize the surface oxygen adsorption capability and enhance the conductivity of the NCS, thereby facilitating the ORR performance. Here, the solvent-free synthesis is also feasible for the synthesis of other non-noble metal element (Fe, Ni, and Zn) decorated nitrogen-doped porous carbon spheres.
Near-IR Luminescence Tuning in a Series of Chalcogenophene Carboxylate-Decorated Neodymium Dimers
Here, the solvothermal synthesis of a series of Nd dimers decorated with various chalcogenophene carboxylates and 2,2':6',2"-terpyridine of the general formula, [Nd 2 (µ-XC 5 H 3 O 2 ) 2 (XC 5 H 3 O 2 ) 4 (N 3 C 15 H 11 ) 2 (H 2 O) 2 ] where X = O, S, Se, and Te, is reported. The solid-state structures were characterized using single-crystal X-ray diffraction (scXRD) and all the complexes are isomorphous, despite substitution of the heterocyclic chalcogen; phase purity was confirmed via powder X-ray diffraction (pXRD). Vibrational spectroscopy was collected and correlations between chalcogen identity and the binding strength of the carboxylate groups of the chalcogenophene ligands with each metal center were shown to be independent of chalcogen identity. All four complexes displayed Nd(III)-based near-IR luminescence and exhibited ligand-sensitized emission. Varying the chalcogenophene chromophore enabled tuning of the sensitizing triplet state energy level, as evidenced by an 8-fold increase in the sensitization of the TeCA-decorated dimer relative to the other chalcogenophene congeners. This behavior was rationalized by comparing the Nd(III) acceptor and ligand donor states across the series. The donor triplet state of each ligand was estimated via low-temperature (77 K) phosphorescence measurements from 1:1 mixtures with Gd(III); these were found to be 24,631 cm –1 for furan-2-carboxylic acid (FCA), 23,764 cm –1 for thiophene-2-carboxylic acid (TCA), 22,548 cm –1 for selenophene-2-carboxylic acid (SeCA), and 21,186 cm –1 for tellurophene-2-carboxylic acid (TeCA). The greater sensitization efficiency of TeCA is the result of well-matched ligand donor and metal acceptor levels and thus suppression of nonradiative back-energy transfer. More broadly, triplet energy level information for these ligands serves as a guide for future application to other target metals based on the electronic properties necessary to effect efficient sensitization.
Solution-Phase Synthesis of Platinum-Decorated Hydrogen Tungsten Bronzes for Hydrogen Atom Transfer from Oxides to Molecules
Hydrogen bronzes can be used as hydrogen donors for the broad class of reactions involving proton-coupled electron transfer (PCET). Here, in this work, we describe a method to prepare platinum-decorated hydrogen tungsten bronzes, Pt@H x WO 3 · n H 2 O with n = 0, 1, and 2, by reacting the pristine oxides at modest temperatures with a mild reducing agent, H 3 PO 2 , and H 2 PtCl 6 in an aqueous solution. We explored the tunability and kinetics of this reaction and compared it with that of archetypal gas–solid hydrogen spillover. We demonstrate that the identity of the noble metal affects the extent of bronze reduction. This suggests that the mechanism proceeds via the adsorption of a hydrogen-atom species on the noble metal. Finally, we explored the ability of the Pt-decorated hydrogen tungsten bronzes to hydrogenate a model H + /e – acceptor, 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO). The bronze phases return to their fully oxidized states along with the subsequent reduction of TEMPO to TEMPOH. Overall, this work demonstrates a solution-phase method to obtain hydrogen bronzes, which can then be used to perform hydrogen transfer reactions, providing a pathway for the use of extended transition metal oxides as stoichiometric reagents for broad classes of hydrogenation reactions.
Electrochemically Assisted Single Crystal Growth of Reduced Preyssler Polyoxometalates Decorated with M 2+ ( M = Co, Ni) and Cubane–Like Ni 4 O 4 Units
Polyoxometalates (POMs) are of great interest to the scientific community, and their reduction and nucleation have been well–established by multi–step techniques. The present study develops an electrochemical approach for simultaneous reduction and nucleation of polyoxometalate–containing solids. Herein we report crystal growth of reduced Preyssler polyoxotungstate–based (anionic formula [NaP 5 W 30 O 110 ] 14– ) new crystalline solids made of Preyssler anions interlinked by Co 2+ and Ni 2+ ions. Crystal nucleation and in situ reduction were achieved at room temperature using a two silver wire electrode setup in various aqueous solutions under constant applied potentials. The POM material was deposited on the cathode, and its structure was characterized by X–ray diffraction techniques. The primary structure type observed involves POMs decorated by disordered Co 2+ /Ni 2+ octahedra and fused into 1–D pillars by additional Co 2+ /Ni 2+ octahedra. Additionally, a secondary phase was observed in the Ni–based reactions, where reduced Preyssler anions are decorated by Ni 4 O 4 cubane–like units. To understand the electrochemical process, polarization curves of the electrolyte solutions are presented, suggesting an applied potential best suited for crystal growth. The work highlights the effectiveness of an electrochemical pathway where nucleation and simultaneous reduction of POMs can make novel reduced POM solids.
Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors
The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electrical material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver(Ag), platinum(Pt) and palladium(Pd) with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The present study is focused on silver decorated MWCNTs dispersed in a polyimide matrix. The Ag-containing MWCNTs were melt mixed into Ultem(TradeMark) and the mixture extruded as ribbons. The extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electrical and electromagnetic properties at 8-12 GHz. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity (epsilon ) and loss factor (epsilon") indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offers a new class of materials with potential applications in electronics, microwave engineering and optics.
Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors
The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electric material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver, platinum and palladium with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The metal-containing MWCNTs were then melt mixed into a polymer matrix and the mixture extruded as ribbons. These extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electromagnetic properties at 8-12 GHz. The present study is focused on silver decorated MWCNTs dispersed in an Ultem polyimide matrix. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity and loss factor (?? and ??) indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offer a new class of materials with potential applications in electronics, microwave engineering and optics.