Browse Articles

Surrogate functionals for machine-learned orbital-free density functional theory

We introduce surrogate functionals: machine-learned energy functionals for orbital-free density functional theory (OF-DFT) which are defined not by universal fidelity to a physical reference, but merely by the requirement that density optimization with a fixed procedure yields the true ground-state density. Helpfully, training surrogate functionals requires only ground-state densities as labels, no energies or gradients away from the ground state. We here propose a gradient-descent-improvement loss that guarantees exponential convergence of the density to the ground state, and combine it with an adaptive sampling scheme that concentrates learning around the optimization trajectories actually visited during inference. On the QM9 and QMugs benchmarks, surrogate functionals achieve density errors competitive with or improving upon the state of the art for fully supervised machine-learned OF-DFT, while eliminating the need for the O(N3) orthonormalization step required by prior work, yielding improved runtime scaling for larger systems.

Decoding vibrational energy transfer in CO–O2 collisions: Vibrational state-to-state rate coefficient datasets on a new potential energy surface

Energy exchanges in collisions between carbon monoxide (CO) and molecular oxygen (O2) are investigated in this paper, and comprehensive datasets of state-to-state rate coefficients for vibration-to-vibration (V–V) and vibration-to-translation/rotation (V–T/R) energy transfer processes are obtained. The data are generated using a mixed quantum–classical (MQC) dynamical method on a newly developed potential energy surface, which is optimized against available experimental data and high-level ab initio calculations. The MQC dataset covers a broad temperature range from 100 to 5000 K, with additional extension through a Gaussian process regression technique to incorporate key V–T/R and near-resonant V–V processes, which include vibrational states of vCO up to 30, as well as the full vibrational ladder of O2 up to its dissociation limit. The results reveal the dominance of V–V kinetics at lower temperatures and the increasing importance of V–T/R processes at higher temperatures. The present dataset addresses a critical gap in the kinetic modeling of CO + O2 collisions in high-temperature gaseous environments.

Single chain expulsion from diblock copolymer micelles with dense corona

We use self-consistent field theory to investigate the free energy landscape for single-chain expulsion from a diblock copolymer micelle with a dense corona. Using the distance from the micelle center-of-mass to the hydrophilic–hydrophobic junction of the chain as the reaction coordinate, we compute the free energy landscape for chain exchange. Our results show that the expulsion free energy barrier scales linearly with both the hydrophobic block length and the solvent selectivity, consistent with recent experiments. To accurately resolve the chain conformation, we introduce a second reaction coordinate: the distance between the junction and the free end of the hydrophobic block, and construct a two-dimensional free energy surface. Using the string method to identify the minimum energy path, we find that all pathways converge to a nearly degenerate reaction channel, irrespective of the initial path. Within this channel, the end-to-end distance of the hydrophobic block exhibits a broad distribution, yet the corresponding expulsion barriers remain nearly indistinguishable. Together, these findings establish a continuum-level theoretical foundation for understanding the hyperstretching mechanism and the transition state ensemble in micellar chain exchange.

Non-equilibrium conformations of dilute star polymers in shear flow

Polymer topology influences the structural and dynamic behavior of macromolecules, particularly under non-equilibrium conditions such as shear flow. As a result, conventional Gaussian chain models fail to capture the complex deformation and relaxation dynamics of polymers with branched architectures. In this study, we present a combination of Brownian dynamics simulations with Gram–Charlier (G–C) expansion analysis to quantify non-Gaussian features using two cumulant-based metrics: the standard deviation σ of the one-dimensional projected configurational distribution, where larger values indicate greater deformation, and the normalized fourth cumulant κ4/σ4, where larger values indicate stronger non-Gaussianity. Focusing on linear and star polymers in dilute solution, we systematically investigate how molecular architecture, finite extensibility, and hydrodynamic interactions (HI) influence their deformation and conformational response in shear flow. Our findings reveal that star polymers exhibit constrained global extension but enhanced local stretching near the core, resulting in reduced deviations from Gaussian behavior compared to linear chains. Finite extensibility imposes an upper limit on bond extension, which suppresses configurational deformation at high shear rates and leads to a non-monotonic trend in κ4/σ4. By contrast, hydrodynamic interactions introduce long-range segmental coupling that enhances coordinated motion and amplifies non-Gaussian character, resulting in higher values of κ4/σ4 under strong shear flow. Together, these results establish a robust framework for characterizing the influence of polymer topology on non-equilibrium conformations, offering new insights into the mechanics of branched polymer systems under flow.

A sensitive method for determining dehydrogenation probabilities at a metal surface

We report a sensitive new approach for tracking surface hydrogen coverage using the novel high-repetition rate implementation of velocity-resolved kinetics in an investigation of methanol-d4 dehydrogenation on Pt(111) to CO and D2. The reactant beam of methanol-d4 had an incidence kinetic energy of 0.46 eV, and the reaction was studied over a surface temperature range of 700–950 K. The reaction probability of methanol dehydrogenation was determined by probing the second-order reaction kinetics of D2 and HD formation, which is directly correlated to the surface hydrogen coverage. Under the conditions of our study, the methanol dehydrogenation probability was found to be low (∼10−3), and the lack of strong temperature dependence is consistent with dehydrogenation via a direct mechanism. Under conditions that favored methanol clustering in the incident methanol beam, the dehydrogenation probability increases significantly at low surface temperatures, which suggests a precursor-mediated mechanism. The possible role of cluster formation in enhancing the trapping probability of methanol is discussed.

Tree tensor networks methods for efficient calculation of molecular vibrational spectra

We develop and employ general tree tensor networks to compute the vibrational spectra for two model systems: a set of 64-dimensional coupled oscillators and acetonitrile. We explore various tree architectures, ranging from the simple linear structure of Matrix Product States (MPS), to trees where only the leaf nodes carry a physical leg—as commonly seen in the underlying ansatz of the multilayer multiconfiguration time-dependent hartree method—and further to more general trees in which all nodes are allowed to possess a physical leg. In addition, we implement locally optimal block preconditioned conjugate gradient methods and inverse iteration methods as eigensolvers. Benchmarking runtime and accuracy shows that all tested topologies can reach high accuracy. For acetonitrile, inverse-iteration refinement brings all 84 computed states below 1 cm−1 error, while the fork-4 tree, a comb-like tree with four backbone nodes, provides the best overall balance between accuracy and cost. MPS remains computationally attractive, whereas more connected trees generally improve accuracy at fixed bond dimension. All numerical simulations were performed using PyTreeNet, a Python package designed for flexible tensor network computations.

Interpretation of permittivity values in vapor deposited thin films of organic glasses

Permittivity values of thin glassy films obtained by physical vapor deposition onto interdigitated electrode cells have been reported to increase considerably after annealing the sample above its glass transition temperature, which cannot be explained by effects of density. While such a change might be interpreted as a transformation to a different structure or altered dynamics, we employ a nonpolar molecular liquid to demonstrate that the apparent permittivity derived from impedance experiments can increase without changes in properties inherent in the sample material. More specifically, it is shown that annealing induces surface flattening that leads to material relocating from on top of the metallic electrode digits to between these digits. For films of thicknesses below 10% of the digit spacing, we demonstrate that the impedance measurement senses predominantly the material located between electrode digits, while being blind to the part of the sample deposited onto the digits. This implies that the apparent permittivity can increase without a change in material properties. A relation that determines film height and deposition rate from the observed capacitance increment is provided.

From full dynamic to pure static: A family of <i>GW</i> -based approximations

We introduce a systematic hierarchy of one-body Green’s function methods derived from the GW approximation, constructed by progressively reducing the dynamical content of the self-energy. Starting from the fully dynamical Dyson formulation, we generate a family of approximations that interpolates between the standard GW approximation and purely static effective single-particle Hamiltonians. This framework enables a controlled investigation of the role of dynamical effects and particle–hole coupling in the description of ionization potentials. Within this unified formalism, the hole and particle branches can be selectively decoupled through downfolding strategies into reduced one-particle spaces. By benchmarking the different members of this hierarchy on molecular ionization energies, we assess their accuracy, numerical robustness, and algorithmic complexity. We demonstrate that consistently derived partially static schemes can yield reliable quasiparticle energies while significantly simplifying the underlying eigenvalue problem. We further introduce a novel static Hermitian self-energy obtained as the static limit of this hierarchy. Despite its conceptually distinct origin, it produces results remarkably close to those of qsGW, thereby providing an alternative static route toward partial self-consistency.

Host–Guest Mismatch Enables Selective Hydrogen Atom Transfer

ABSTRACT Endogenous binding of molecular guests inside cavities of their hosts has been routinely utilized in enzymatic and supramolecular catalysis. In contrast, exogenous binding‐where a guest selectively associates with the exterior surface, rather than the cavity, of its host owing to their size mismatch‐remains a largely unexplored paradigm for controlling the selectivity of chemical reactions. Here, we report that the exogenous binding between natural cyclodextrins (CDs) and a polyoxometalate catalyst leads to high site‐selectivity in hydrogen atom transfer between them. The decatungstate anion (W 10 O 32 4– ), a photoactive polyoxometalate capable of abstracting hydrogen atoms from C–H bonds on organic molecules, was found to associate noncovalently with CDs in aqueous solution. The large size of W 10 O 32 4– , however, precludes the formation of deep inclusion complexes and confines its interactions with the narrow rim of CDs, as evidenced by 1 H NMR titration and x‐ray crystallography. This exogenous association increases the effective local concentration of W 10 O 32 4– near the C6–H bonds, accelerating HAT at these positions upon photoexcitation and rendering C6 functionalization kinetically dominant over slower, less selective background pathways. The host‐guest mismatch approach offers a general platform for the selective, one‐step ligations of CDs onto natural products, drugs, fluorescent probes as well as “click” compatible molecular scaffolds.

(SOS1-)PBE-DH-INVEST double hybrid functionals for INVEST systems: Validation for azaphenalene compounds

INVEST systems (INVErted Singlet–Triplet excited-state energies) have attracted increasing interest due to their potential relevance in organic light-emitting diodes and photocatalytic applications. However, their accurate theoretical description remains challenging because the singlet–triplet energy gap, ΔEST, is strongly governed by electron-correlation effects and double-excitation contributions, which are not properly captured by conventional time-dependent density functional theory approaches. In this work, the recently developed double-hybrid density functional PBE-DH-INVEST, together with its spin-opposite-scaled variant SOS1-PBE-DH-INVEST, is assessed for the AP117 benchmark set of azaphenalene derivatives. Excitation energies for the S1 ← S0 and T1 ← S0 transitions, as well as the corresponding ΔEST values, were computed using the aug-cc-pVDZ basis set within the Tamm–Dancoff approximation and compared against CC2 reference data. The results show that PBE-DH-INVEST provides a robust description of both excitation energies and singlet–triplet gaps, with low deviations relative to the reference values and a marked improvement over the corresponding self-consistent hybrid treatment lacking double-excitation corrections. In particular, the inclusion of the Δ(D) contribution for double excitations is shown to be essential for reproducing the inverted energetic ordering characteristic of INVEST systems. The SOS1-PBE-DH-INVEST variant also yields competitive results at a reduced formal computational cost, although with slightly larger errors.

Electride Formation of (Ca _1– <i> _x </i> Sr <i> _x </i> ) ₃ CrN ₃ Induced by Negative Chemical Pressure

ABSTRACT Electrides are materials in which electrons occupy interstitial sites and act as anions. Conventional strategies for stabilizing electrides have relied on either anion removal or the application of high pressure. Here, we show that in (Ca 1– x Sr x ) 3 CrN 3 , negative chemical pressure induces electride formation together with a reconstruction of the crystal framework. Structural analyses reveal that overbonded Cr undergoes oxidation, releasing electrons while driving a redistribution of nitrogen within the framework, which reconstructs the Ca sublattice into one‐dimensional (1D) octahedral chains that host interstitial electrons. High‐pressure experiments and first‐principles calculations further demonstrate that external pressure destabilizes the electride phase, whereas negative chemical pressure stabilizes it. Moreover, (Ca 0.35 Sr 0.65 ) 3 CrN 3 exhibits metallic‐like conduction, providing the first evidence for itinerant anionic electrons in a 1D electride. The enhanced itinerancy is attributed to the short interstitial‐electron separation and the resulting increase in electride‐band bandwidth. These findings establish negative chemical pressure as a new design principle for electrides and identify interstitial‐electron separation as a key parameter governing electron itinerancy in low‐dimensional electrides.

Effect of pre-shear and dispersity on crystallization of a model polymer with soft pair interactions using molecular dynamics simulations

Polymer crystallization is a process of great interest in both fundamental theory and industrial settings, particularly in polymer processing and applications involving semi-crystalline materials. The effect of processing on the initial stages of crystallization is not fully understood. Our study investigates the influence of pre-shear on monodisperse melts and bidisperse blends of a generic, segmentally coarse-grained polymer model. Through molecular dynamics simulations, we explore how polydispersity affects crystallization, where we found that the addition of short chains to a melt of longer chains increased the end-of-simulation crystallinity by about 10% and increased the initial growth rate by roughly a factor of two. In contrast, however, pre-shearing the hot melt before quenching only showed a minor increase in both growth rates and final crystallinity, except in monodisperse melts of short chains. Crystal grain shapes were most influenced by pre-shearing monodisperse melts, where both asphericity and prolateness decreased. In addition, we determined topological connectivity of crystal grains through tie- and loop-chain analysis. Again, only monodisperse melts showed a significant increase of tie chain fractions with pre-shear, while all other systems showed only modest increases. Our findings provide insight into the changes of crystallinity and cluster morphologies that emerge when pre-sheared, offering a deeper understanding of the initial crystallization processes in polymer melts when subjected to pre-shear.

Tailoring Photochromism Beyond Human Eye Visibility: On/Off Switchable NIR Absorption in an Aluminosilicate

ABSTRACT Photochromic materials are able to change reversibly between two colors. The color change is triggered by ultraviolet radiation and reversed by white light and/or heating. Inorganic photochromes have been thought to operate with fixed wavelengths only, and because of this, their usage has been considered less convenient than that of their organic counterparts, even if the inorganic ones would show a much higher durability in applications. High‐tunability within the whole visible wavelength range was recently demonstrated by some of us for hackmanites, a family of inorganic aluminosilicates. Here, we demonstrate that a davyne‐type structure constitutes the first photochromic material exhibiting absorption exclusively in the near‐infrared region, without accompanying visible color changes, thereby enabling fully invisible photochromism beyond human perception. Furthermore, we show that the invisible photochromic changes can be detected with a simple camera setup. This is the first material that exhibits invisible near‐infrared reversible photochromism, and we discuss its potential for tagging applications.

Tribological universality in compressed polymer brushes

Compressed polymer brushes exhibit mutual interpenetration that is linked to the tribological properties of brush-coated surfaces. Interpenetration is quantified by the overlap function, defined as the product of the density profiles of two opposing brushes. Using numerical self-consistent field calculations, we show that the shape of the overlap function is remarkably invariant across a broad class of symmetric and asymmetric brush pairs. The brush parameters that varied include chain length, grafting density, chain stiffness, and degree of branching. In the non-draining approximation and at low shearing rates, the overlap integral defines the sliding friction force. We find that normalizing the friction force vs external pressure curves by their values at a fixed reference pressure collapses the data onto a universal master curve for all brush pairs sharing the same equation of state, regardless of all the other parameters, which should simplify the design of lubricating coatings.

Long-term cultural continuity across the Neanderthal–modern human sequence at Üçağızlı II Cave, northern Levant

We present evidence from Üçağızlı II Cave in the northern Levant, Türkiye, documenting the sequential occupation by Neanderthals ( Homo neanderthalensis ; 77–59 ka) and modern humans ( Homo sapiens ; 59–47 ka). The combined evidence of human fossils, faunal and floral remains, lithics, and manuports demonstrates significant behavioral and technological continuity across this taxonomic sequence, characterized by consistent subsistence strategies and the persistent selection and transport of specific nondietary mollusk shells. The lithic assemblages largely align with late Middle Paleolithic traditions, exhibiting characteristic Mousterian variants. The association of diagnostic human fossils with these archaeological remains demonstrates that the shift from Neanderthals to modern humans occurred within a cultural continuum. Our findings suggest shared behaviors between Neanderthals and modern humans that extended beyond subsistence to include nonutilitarian behaviors within the specific geographic and temporal context studied here.

Triadic Sites Drive Tandem CO ₂ ‐to‐Ethanol Conversion by Steering *CO Coverage and *COH Intermediate Formation

ABSTRACT Single metal‐coordinated nitrogen‐doped carbon (M 1 ‐NC) materials hold great promise for electrocatalytic CO 2 reduction, yet the precise modulation of their nitrogen configurations to steer ethanol selectivity remains a formidable challenge. Here, we designed Cu 1 ‐NC anchored on a carbon support featured with a high pyrrolic‐N to pyridinic‐N ratio (CuN 4 /pr‐h‐NC), which enables an exceptional Faradaic efficiency (FE) of 79.6% for ethanol. Experimental and theoretical studies reveal that pyrrolic‐N and pyridinic‐N synergize with Cu sites to form novel triadic sites, which regulate the potential‐determining step (PDS) from the traditional C–C coupling step to the protonation step of *CO to *COH. Pyrrolic N boosts *CO surface coverage, after which *CO migrates to neighboring pyridinic N sites for hydrogenation to *COH. The resulting *COH readily couples with another *CO at the single Cu site, driving selective ethanol formation. Due to the single‐metal‐surface‐independence of PDS, this mechanism extends to metals traditionally considered inactive for C–C coupling (M = Fe, Co, Ni, Zn). A positive correlation is observed between the ethanol FE and the pyrrolic N/pyridinic N ratio across the series, with ZnN 4 /pr‐h‐NC reaching 71.8% at –0.5 V versus RHE. This work establishes an ensemble site engineering strategy to rationally steer CO 2 to ethanol pathways for M 1 ‐NC electrocatalysts.

On the role of symmetry in quenching OH tunneling in 2,6-dimethylphenol

We model the spectroscopy of the two methyl torsional degrees of freedom coupled to the OH torsional motion in 2,6-dimethylphenol. Recent gas-phase rotational transitions [Welsh et al., J. Phys. Chem. Lett. 17, 3749–3758 (2026)] have been interpreted to be the result of certain symmetry states of the methyl groups leading to the quenching of the OH torsional motion. Both a three-dimensional model and an adiabatic model, in which the OH torsion is treated as the slow mode, are developed to test these conjectures. Good agreement is found between the exact and approximate adiabatic models. The adiabatic model is developed to interpret and elucidate the key couplings leading to the quenching of the tunneling splitting.

Enantioselective Hydrosilylation of Diverse Allenes via Nickel Catalysis

ABSTRACT Enantioselective hydrosilylation of allenes remains a significant challenge with a limited scope due to the difficulties in controlling both regioselectivities and enantioselectivities, despite it representing one of the most efficient manners for the preparation of optically pure allylsilanes. Here, we report a general platform for the efficient and modular preparation of diverse allylsilanes via nickel‐catalyzed hydrosilylation of various allene derivatives, including mono‐substituted allenes and 1,3‐disubstituted allenes. Enabled by a newly developed SPSiOL‐derived diphosphinite ligand (SPSiOP), hydrosilylation of mono‐substituted allenes has been realized with excellent regioselectivity and enantioselectivity. Moreover, the first kinetic resolution of racemic 1,3‐disubstituted allenes has been disclosed using a commercially available chiral QuinoxP* ligand, affording a series of secondary allylsilanes with high stereo induction ( S factor up to 133). The resulting enantioenriched allylsilanes are highly synthetically useful, which has been demonstrated by a variety of transformations of the silyl and alkene functional groups, culminating in efficient synthesis of silacycles and formal synthesis of several bioactive molecules.

Extraction of slip velocity in NEMD Couette flow systems using frictional dissipation

Velocity slip at the solid–fluid (SF) interface plays a key role in fluid transport at the nanoscale, and the SF friction coefficient has been extensively studied because it indicates the degree of slippage. Owing to the scale of this phenomenon, molecular dynamics (MD) simulations are commonly employed using two major approaches: the Green–Kubo integral method in equilibrium MD (EMD) and the direct calculation of friction force and slip velocity in non-equilibrium MD (NEMD) systems under shear. Regarding the latter, a strict definition of the slip velocity is missing due to the nonzero thickness of the boundary at the microscale, and the average velocity of the first adsorption layer or the velocity at the boundary obtained by extrapolation or interpolation is often used. In this study, we propose an alternative description of the slip velocity based on a thermal perspective from the two different scales, i.e., at the macroscale, frictional heat is defined as the product of the friction force and slip velocity, whereas at the microscale, it can be expressed as the sum of the works exerted on the fluid and solid by each other. By combining the two different scales, we defined the slip velocity based on the dissipation induced at the SF interface under shear, which avoids the arbitrariness in the slip velocity at the microscale.

Correction to “Concerted Harnessing of Interfacial Concentration Field and Electronic Field for Boosting Electrocatalytic Semi‐Hydrogenation of Alkynol”