Inspired by the recent discovery of metallic spin supersolidity and its giant magnetocaloric effect in the rare-earth alloy EuCo2Al9, we perform a combined study through electronic structure analysis, effective spin model construction, and Monte Carlo simulations on a stacked triangular lattice (STL), and reveal a novel mechanism for the emergence of 3D spin supersolid in a metallic antiferromagnet. From first-principles inputs, we derive a minimal spin model on a STL, which arises from the interplay between Ruderman-Kittel-Kasuya-Yosida and dipolar interactions and accurately reproduces the experimental thermodynamics. Based on the STL model, we identify a ground state that simultaneously breaks discrete lattice translational symmetry and continuous spin-rotational symmetry-the hallmark of a spin supersolid. Furthermore, we present the field-temperature phase diagram of the 3D STL model and discuss the various magnetic phases and associated phase transitions. Under zero field, the spin supersolid Y order establishes in two steps: an upper transition at TN1, where an emergent U(1) symmetry appears and the system enters a fluctuating collinear regime, followed by a lower transition at TN2 into the spin supersolid Y phase. In contrast, the supersolid V phase undergoes a single phase transition at TNV . Our results not only provide a comprehensive theoretical understanding of the metallic spin supersolid reported for EuCo2Al9 but also pave the way for further experimental investigations into its supersolid transitions and universality class.

Near a quantum critical point (QCP), the low-temperature thermodynamics follows universal scaling laws. Using copper sulfate pentahydrate-a canonical spin-1/2 antiferromagnetic Heisenberg chain compound-we report the observation of a universal magnetocaloric effect (MCE) near a field-driven QCP. Remarkably, in the 1D quantum-critical regime, we obtain the universal magnetocaloric scaling function via adiabatic demagnetization measurements, which agrees with the analytical solutionof the critical 1D Fermi gas. This establishes the copper sulfate crystal as an ideal platform for studying quantum criticality and universal phenomena. Upon further cooling, our MCE and nuclear magnetic resonance measurements reveal a dimensional crossover to a 3D quantum-critical regime of the Bose-Einstein condensation (BEC) universality class, characterized by the scaling lawand a clear data collapse of the magnetic Grüneisen ratio with the 3D Bose-gas scaling function. Practically, this quantum-critical MCE enables cooling to 68.7 mK near the QCP and achieves a lowest temperature of 12.8 mK at zero field without the need for helium-3. Our work identifies a universal MCE in a common compound, establishing this magnon BEC system as a prototype quantum-critical coolant and a platform for next-generation millikelvin refrigeration.

The discovery of spin supersolid and its giant magnetocaloric effect has opened a new arena in frustrated quantum magnets and cutting-edge cryogenics.The intermetallic EuCo2Al9(ECA),for the first time,extends this intriguing phase from Mott insulators to a highly conductive metal.In this work,we systematically study the electrical transport properties of EC A,where itinerant electrons serve as a sensitive probe of the spin su-persolid state.We observe anomalies both in the temperature-dependent resistivity and in the field-dependent magnetoresistance and Hall signals,which are attributed to the response of electrons to the Eu2+spins and their fluctuations.Moreover,Shubnikov-de Haas quantum oscillations at high magnetic fields reveal pronounced band splitting in the spin-polarized state.Our results reveal an intimate correspondence between electrical transport and magnetic transitions in ECA,deepening the understanding of this metallic spin supersolid.

A combination of biomedical imaging and photodynamic therapy (PDT) in a single nanomaterial would be a breakthrough in nanomedicine. However, devising a single photosensitizer capable of efficient PDT without requiring an external oxygen source under typically hypoxic tumor conditions, combined with high photostability, biocompatibility, and renal clearance, remains a challenge. Atomically precise ultrasmall (<2 nm) gold nanoclusters (AuNCs) are emerging as potential multifunctional biomedicines, encompassing imaging, diagnosis, and therapy in a single nanoplatform. Herein, we report bioderived cellulose nanocrystal-supported gold nanoclusters (CNC-AuNCs) with selective mono or multiheteroatom (Ag, Pd, and Pt) substitution at the core of the nanoclusters. The replacement of one or more gold atoms significantly modulates their emission wavelengths, photoluminescence quantum yields, as well as excited-state relaxation kinetics. These materials can easily penetrate the cells, accumulating in the cytoplasm and emitting bright luminescence. While the nanocomposites are highly biocompatible, they can produce reactive oxygen species (ROS) through the formation of free radicals (O2-· and ·OH) upon exposure of light. The synergistic effect of the light absorption by the matrix and the diverse excited-state relaxation pathways of the nanoclusters results in the efficient generation of ROS in variable concentrations, ultimately leading to the complete destruction of targeted cancer cells via Type-I photodynamic effect. The optimal ROS efficacy combined with minimal cytotoxicity suggests a universal strategy for developing strong PDT-I agents, paving the way for versatile nanomaterials in theranostic applications.

Constructing accessible active sites on the surface of catalysts at the atomic precision remains challenging in heterogeneous single-nanocluster catalysis. Leveraging the differences in coordination preferences between various metals and ligands, a heterometallic coordination hybridization (HCH) protocol was proposed to manipulate the stable and accessible active sites on the surface of single-nanocluster catalysts. A homoleptic superatomic nanocluster [(AuCu)71(m-MBT)46](CF3SO3)3 (short as (AuCu)71 and m-MBT = 3-methylbenzenethiol) was synthesized in high yield, and its structure was determined by single-crystal X-ray diffraction. Benefiting from the HCH strategy, (AuCu)71 features four open, accessible, and stable dual-Au sites on its surface. Notably, heterogeneous single-nanocluster catalyst (AuCu)71/XC-72 (XC-72 is carbon support) exhibited excellent catalytic performance for denitrative C-O coupling under mild conditions (60 °C, atmosphere). The turnover numbers and turnover frequencies reached record high values of 2.88 × 106 and 3.48 × 105 h-1, respectively, which are four orders of magnitude higher than those observed for the well-established Pd/C system. The remarkable catalytic performance of (AuCu)71 was attributed to the exposed dual-Au sites, which facilitated the adsorption of deprotonated phenol and its derivatives via Au-O interactions, guided the proximity of nitroarenes rather than being commonly absorbed simultaneously on active sites, and exhibited exceptional durability of the catalyst. The HCH protocol provides new idea for the rational design and construction of heterogeneous metal catalysts with well-defined accessible active sites.

Syngas conversion into higher alcohols represents a promising avenue for transforming coal or biomass into liquid fuels. However, the commercialization of this process has been hindered by the high cost, low activity, and inadequate C2+OH selectivity of the catalysts. Herein, we have developed Cu/Co carbon wood catalysts, offering a cost-effective and stable alternative with superior selectivity for catalytic conversion. The formation of Cu/Co nanoparticles was found, influenced by water-1,2-propylene glycol ratios in the solution, resulting in bidisperse nanoparticles. The Cu/Co-CW-W1P1 catalyst (the ratio between water and 1,2-propanediol is 0.5:0.5) exhibited a remarkable CO conversion rate of 74.8% and a selectivity of 58.7% for C2+OH, primarily comprising linear primary alcohols. This catalyst demonstrated enduring stability and selectivity under industrial conditions, maintaining its efficacy for up to 350 h of operation. We also employed density functional theory (DFT) to analyze selectivity, particularly focusing on the binding strength of CO, a crucial intermediate for subsequent reactions leading to the formation of alcohols. DFT identified the pathway of CH x and CO coupling, ultimately yielding C2H5OH. This computational understanding, coupled with the high performance of the Cu/Co-carbon wood catalyst, paves the way to develop catalytically selective materials tailored for higher alcohol production from a nature-based source.

First principles-based computational and theoretical methods are constantly evolving trying to overcome the many obstacles towards a comprehensive understanding of electrochemical processes on an atomistic level. One of the major challenges has been the determination of reaction energetics under a constant applied potential. Here, a theoretical framework was proposed applying standard electronic structure methods and extrapolating to the infinite-cell size limit where reactions do not alter the potential. More recently, grand-canonical modifications to electronic structure methods which hold the potential constant by varying the number of electrons in a finite simulation cell have gotten increasingly popular. In this perspective, we show that these two schemes are thermodynamically equivalent. Further, we link these methods to ones based on capacitive models of the interface, in the limit that the capacitance of the charging components (whether continuum or atomistic) are equal and invariant along the reaction pathway. We further benchmark the three approaches with an example of alkali cation adsorption on Pt(111) proving that all three approaches converge in the cases of Li, Na and K. For Cs, however, strong deviation from the ideal conditions leads to a spread in the respective results. We discuss the latter by highlighting the cases of broken equivalence and assumptions among the approaches.

Energy- and resource-efficient electrocatalytic water splitting is of paramount importance to enable sustainable hydrogen production. The best bulk catalyst for the hydrogen evolution reaction (HER), i.e., platinum, is one of the scarcest elements on Earth. The use of raw material for HER can be dramatically reduced by utilizing nanoclusters. In addition, nanoalloying can further improve the performance of these nanoclusters. In this paper, we present results for HER on nanometer-sized ligand-free AuPt nanoclusters grafted on carbon nanotubes. These results demonstrate excellent monodispersity and a significant reduction of the overpotential for the electrocatalytic HER. We utilize atomistic machine learning techniques to elucidate the atomic-scale origin of the synergistic effect between Pt and Au. We show that the presence of surface Au atoms, known to be poor HER catalysts, in a Pt(core)/AuPt(shell) nanocluster structure, drives an anomalous enhancement of the inherently high catalytic activity of Pt atoms.

The development of bifunctional catalysts to diminish the kinetic barriers associated with the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is regarded as a viable approach to augmenting the efficacy of zinc-air batteries (ZABs). This research presents a methodology that integrates metal clusters and single atoms, employing ZIF-7-NH2 as the foundational material to affix metals onto derivatives, resulting in the creation of g-SAFe-Cun. Aberration-corrected transmission electron microscopy (AC-TEM) revealed discrete bright spots corresponding to iron atoms and copper cluster sites, with their bonding interactions substantiated by extended X-ray absorption fine structure (EXAFS) analysis. Electrochemical assessments indicated that g-SAFe-Cun possesses outstanding bifunctional catalytic capabilities, as evidenced by a ΔE value of 0.578 V. When integrated into a liquid-phase zinc-air battery with g-SAFe-Cun serving as the air cathode, the system exhibited remarkable long-term stability, enduring over 2100 cycles at a current density of 10 mA·cm-2, which equates to an operational duration surpassing 350 h. Density functional theory (DFT) computations elucidated that the incorporation of Cu clusters induces substantial spin polarization of the Fe 3d orbitals, thereby increasing the quantity of unpaired electrons and facilitating the transition of Fe to a high-spin state, which aids in the activation of triplet O2 to generate active intermediates. Furthermore, the robust orbital coupling between the Cu clusters and Fe atom leads to a reduction in orbital energy levels, which in turn diminishes the adsorption of *OH and enhances catalytic activity. The economic and accessibility benefits of employing non-noble-metal materials are substantial, markedly reducing costs and offering promising prospects for widespread commercial deployment.

First principles-based computational and theoretical methods are constantly evolving trying to overcome the many obstacles towards a comprehensive understanding of electrochemical processes on an atomistic level. One of the major challenges has been the determination of reaction energetics under a constant potential. Here, a theoretical framework was proposed applying standard electronic structure methods and extrapolating to the infinite-cell size limit where reactions do not alter the potential. Today, electronically grand canonical modifications to electronic structure methods, holding the potential constant by varying the number of electrons in a finite simulation cell, become increasingly popular. In this perspective, we show that these two schemes are thermodynamically equivalent. Further, we link these methods to capacitive models of the interface, in the limit that the capacitance of the charging components (whether continuum or atomistic) are equal and invariant along the reaction pathway. We benchmark the three approaches with an example of alkali cation adsorption on Pt(111) showing that all three approaches converge in the cases of Li, Na and K. For Cs, however, strong deviation from the ideal conditions leads to a spread in the respective results. We discuss the latter by highlighting the cases of broken equivalence and assumptions among the approaches.

Finding low-energy structures of ligand-protected clusters is challenging due to the enormous conformational space and the high computational cost of accurate quantum chemical methods for determining the structures and energies of conformers. Here, we adopted and utilized a kernel rigid regression based machine learning method to accelerate the search for low-energy structures of ligand-protected clusters. We chose the Au25(Cys)18 (Cys: cysteine) cluster as a model system to test and demonstrate our method. We found that the low-energy structures of the cluster are characterized by a specific hydrogen bond type in the cysteine. The different configurations of the ligand layer influence the structural and electronic properties of clusters.

We review the GPAW open-source Python package for electronic structure calculations. GPAW is based on the projector-augmented wave method and can solve the self-consistent density functional theory (DFT) equations using three different wave-function representations, namely real-space grids, plane waves, and numerical atomic orbitals. The three representations are complementary and mutually independent and can be connected by transformations via the real-space grid. This multi-basis feature renders GPAW highly versatile and unique among similar codes. By virtue of its modular structure, the GPAW code constitutes an ideal platform for implementation of new features and methodologies. Moreover, it is well integrated with the Atomic Simulation Environment (ASE) providing a flexible and dynamic user interface. In addition to ground-state DFT calculations, GPAW supports many-body GW band structures, optical excitations from the Bethe-Salpeter Equation (BSE), variational calculations of excited states in molecules and solids via direct optimization, and real-time propagation of the Kohn-Sham equations within time-dependent DFT. A range of more advanced methods to describe magnetic excitations and non-collinear magnetism in solids are also now available. In addition, GPAW can calculate non-linear optical tensors of solids, charged crystal point defects, and much more. Recently, support of GPU acceleration has been achieved with minor modifications of the GPAW code thanks to the CuPy library. We end the review with an outlook describing some future plans for GPAW.

Plasmon resonances in metal nanoparticles provide a powerful way to amplify molecular circular dichroism (CD). In this paper, we use time-dependent density-functional theory to systematically investigate the CD enhancement of a molecule on a silver nanoparticle or sandwiched between two silver nanoparticles. We find that in both systems the enhancement increases roughly as the square root of the number of Ag atoms up to the considered 923-atom Ag particle. The enhancement in dimers is more significant. In addition, we analyze the influences of the molecular orientation, molecule-nanoparticle distance, and the molecular coverage on the CD enhancement.

A strategy is presented for the machine-learning emulation of electronic structure calculations carried out in the electronically grand-canonical ensemble. The approach relies upon a dual-learning scheme, where both the system charge and the system energy are predicted for each image. The scheme is shown to be capable of emulating basic electrochemical reactions at a range of potentials, and coupling it with a bootstrap-ensemble approach gives reasonable estimates of the prediction uncertainty. The method is also demonstrated to accelerate saddle-point searches, and to extrapolate to systems with one to five water layers. We anticipate that this method will allow for larger length- and time-scale simulations necessary for electrochemical simulations.

Finding low-energy conformers of organic molecules is a complex problem due to the flexibilities of the molecules and the high dimensionality of the search space. When such molecules are on nanoclusters, the search complexity is exacerbated by constraints imposed by the presence of the cluster and other surrounding molecules. To address this challenge, we modified our previously developed active learning molecular conformer search method based on Bayesian optimization and density functional theory. Especially, we have developed and tested strategies to avoid steric clashes between a molecule and a cluster. In this work, we chose a cysteine molecule on a well-studied gold-thiolate cluster as a model system to test and demonstrate our method. We found that cysteine conformers in a cluster inherit the hydrogen bond types from isolated conformers. However, the energy rankings and spacings between the conformers are reordered.

Ultra-small luminescent gold nanoclusters (AuNCs) have gained substantial interest owing to their low photobleaching and high biocompatibility. While the substitution of silver for gold at the central core of AuNCs has shown significant augmentation of photoluminescence with enhanced photostability, selective replacement of the central atom by silver is, however, energetically inhibited. Herein, a new strategy for in situ site-selective Ag-doping exclusively at the central core of AuNCs using sulphated colloidal surfaces as the templates is presented. This approach exceedingly improves the photoluminescence quantum efficiency of AuNCs by eliminating nonradiative losses in the multi-step relaxation cascade populating the emissive state. Density functional theory predicts the mechanism of specific doping at the central core, endorsing the preferential bonding between Ag+ ions and sulphates in water. Finally, the generic nature of the templating concept to allow core-specific doping of nanoclusters is unraveled.

An atomically precise ultrasmall Au(I) 6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6‐(dibutylamino)‐1,3,5‐triazine‐2,4‐dithiol (TRZ) with HAuCl 4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I) 6 TRZ 3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH 4 and NaBH 3 CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I) 6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand‐to‐metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron‐accepting ground state properties allow p ‐doping of 2D field‐effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown.

We find that ion creation/destruction dominates the behavior of electrochemical reaction barriers, through grand-canonical electronic structure calculations of proton-deposition on transition metal surfaces. We show that barriers respond to potential in a nonlinear manner and trace this to the continuous degree of electron transfer as an ion is created or destroyed. This explains both Marcus-like curvature and Hammond-like shifts. Across materials, we find the barrier energy to be driven primarily by the charge presented on the surface, which in turn is dictated by the native work function, a fundamentally different driving force than non-electrochemical systems.

Identifying low-energy conformers with quantum mechanical accuracy for molecules with many degrees of freedom is challenging. In this work, we use the molecular dihedral angles as features and explore the possibility of performing molecular conformer search in a latent space with a generative model named variational auto-encoder (VAE). We bias the VAE towards low-energy molecular configurations to generate more informative data. In this way, we can effectively build a reliable energy model for the low-energy potential energy surface. After the energy model has been built, we extract local-minimum conformations and refine them with structure optimization. We have tested and benchmarked our low-energy latent-space (LOLS) structure search method on organic molecules with $5-9$ searching dimensions. Our results agree with previous studies.