The moderate synthesis conditions of CeH9 under cold compression demonstrate its remarkable chemical precompression effect, while the single occupied 4 f electron configuration of Ce contributes to the rich chemical and physical properties observed in cerium-bearing compounds. In collaboration with machine-learning-accelerated crystal structure prediction, we predicted a thermodynamically stable superconducting phase CeSc2H24at 200 GPa. With considering more accurate quantum anharmonic effects, the thermodynamically stable pressure of CeSc2H24 is further decreased to 117 GPa, at which pressure it exhibits a high superconducting critical temperature (Tc) of <^>210 K. We found a different framework of bonding theory for hydrogen-based superconductors where strong metallic bonds in hydrides originate from near-free electronic states between the highest effective energy level and the Fermi level. Specifically, the delocalization of Ce-4f orbitals in CeSc2H24 provided a number of near-free electrons, thereby greatly enhancing metallic bonds and making the system energetically much more favorable. Our theory for CeSc2H24emphasizes the non-negligible role of metallic bonding in hydrides, which paves the way for developing high-temperature superconductors under experimentally accessible pressures.

Recent advances in X-ray free-electron laser diagnostics have enabled direct probing of electronic properties under extreme pressures and temperatures, such as those encountered in stellar interiors and inertial confinement fusion experiments, challenging theoretical models for interpreting experimental data. Kohn-Sham density functional theory (KSDFT) has been successfully applied to analyze experimental X-ray scattering measurements, but its high computational cost renders routine application impractical. Orbital-free DFT (OFDFT) is a substantially more efficient alternative, with computational cost scaling linearly with system size and a weak temperature dependence, yet it often lacks the accuracy required for describing the electronic density and the electron-ion structure factor. Overcoming this limitation, we present a non-empirical KS-assisted orbital-free density functional framework for calculations under extreme conditions, which enables efficient OFDFT simulations with KSDFT-level accuracy for electron densities, electron-ion structure factors, and equations of state across a broad range of conditions. Benchmark comparisons with quantum Monte Carlo data for dense hydrogen and validation against Rayleigh weight measurements of hot dense beryllium demonstrate the reliability of the framework and speedups of up to several hundred times compared with KSDFT. We further show that even at temperatures of the order of 100 eV, quantum nonlocality remains essential for correctly describing the electron-ion structure factor in dense hydrogen.

Electrides, featuring interstitial anionic electrons (IAEs) in lattice cavities, offer a novel platform for superconductivity research, yet their electronic behavior, nature, and role of IAEs in Cooper pairing formation remain unclear due to challenges in direct observation. Here, using angle-resolved photoemission spectroscopy (ARPES), transport measurements, and first-principles calculations, we demonstrate that IAEs in electride La3In exhibit dual anionic and near-free electron characteristics. With our established effective local potential model, we trace that IAEs are located near Fermi-level states above potential barriers, forming a Fermi sea susceptible to La-derived phonon scattering, triggering superconductivity at 9.4 K. ARPES combined with high-resolution XRD measurements on oxygen-treated samples confirms the spatial distribution and energy dispersion of IAEs, aligning with our theoretical predictions. Oxygen treatment-induced reduction of near-free electrons correlates with diminished superconductivity, directly linking IAEs to electron-phonon coupling. Our study resolves the long-standing ambiguity regarding the nature of IAEs, elucidates their role in driving phonon-mediated superconductivity, and lays the foundation for exploring electride-based superconductors.

Electron accumulation in interatomic regions is a fundamental quantum phenomenon dictating chemical bonding and material properties, yet its origin remains elusive across disciplines. Here, we report a quantum accumulation effect – potential-barrier affinity (PBA) – revealed by solving the Schrödinger equation for a crystalline potential. PBA effect drives significant interatomic electron accumulation when electron energy exceeds the barrier maximum. This effect essentially enhances interatomic electron density, governing microstructures and properties of condensed matter. Our theory overturns the traditional wisdom that the interstitial electron localization in electride requires potential-well constraints or hybrid orbitals, and it serves as the fundamental mechanism underlying the formation of conventional solid bonding. This work delivers a paradigm shift in understanding electron distribution and establishes a theoretical foundation for the microscopic design of material properties.

The discovery of superconducting electrides, characterized by interstitial anionic electrons (IAEs) residing in lattice cavities, has established a distinctive platform for investigating superconductors. Yet the superconducting origin and the fundamental role of IAEs in Cooper pairing formation remain poorly understood due to the challenges in directly observing IAEs. Here, combining angle-resolved photoemission spectroscopy (ARPES), transport measurements, and first-principles calculations, we certify that the IAEs in electride La3In (Tc = 9.4 K) exhibit a dual nature as both anions and free electrons. With the finite-depth potential well model, we trace that IAEs originate from electronic states near the Fermi level located above potential barriers, forming a Fermi sea susceptible to scattering by La-derived phonons, triggering superconductivity. ARPES combined with high-resolution XRD measurements on oxygen-treated samples directly reveals IAEs' spatial distribution and energy dispersion from interstitial sites with the consistent energy value predicted by our theory model. The concomitant diminution of free electrons upon oxygen treatment, leading to a marked reduction in superconductivity, further provides compelling experimental evidence that IAEs actively participate in electron-phonon coupling. Our findings resolve the long-standing ambiguity regarding the electronic nature of IAEs, elucidate their enhancing superconductivity in the phonon-mediated mechanism, and provide a foundation for exploring advanced electride-based superconductors.

Nonlocal kinetic energy density functionals (KEDFs) with density-dependent kernels are currently the most accurate functionals available for orbital-free density functional theory (OF-DFT) calculations. However, despite advances in numerical techniques and using only (semi)local density-dependent kernels, nonlocal KEDFs still present substantial computational costs in OF-DFT, limiting their application in large-scale material simulations. To address this challenge, we propose an efficient framework for reconstructing nonlocal KEDFs by incorporating the density functional tight-binding approach, in which the energy functionals are simplified through a first-order functional expansion based on the superposition of free-atom electron densities. This strategy allows the computationally expensive nonlocal kinetic energy and potential calculations to be performed only once during the electron density optimization process, significantly reducing computational overhead while maintaining high accuracy. Benchmark tests using advanced nonlocal KEDFs, such as revHC and LDAK-MGPA, on standard structures including Li, Mg, Al, Ga, Si, III-V semiconductors, as well as Mg_50 and Si_50 clusters, demonstrate that our method achieves orders-of-magnitude improvements in efficiency, providing a cost-effective balance between accuracy and computational speed. Additionally, the reconstructed functionals exhibit improved numerical stability for both bulk and finite systems, paving the way for developing more sophisticated KEDFs for realistic material simulations using OF-DFT.

High-mobility semiconductor nanotubes have demonstrated great potential for applications in high-speed transistors, single-charge detection, and memory devices. Here we systematically investigated the electronic properties of single-walled boron antimonide (BSb) nanotubes using first-principles calculations. We observed that rolling the hexagonal boron antimonide monolayer into armchair (ANT) and zigzag (ZNT) nanotubes induces compression and wrinkling effects, significantly modifying the band structures and carrier mobilities through band folding and pi*-sigma* hybridization. As the chiral index increases, the band gap and carrier mobility of ANTs decrease monotonically, where electron mobility consistently exceeds hole mobility. In contrast, ZNTs exhibit a more complex trend: the band gap first increases and then decreases, and the carrier mobility displays oscillatory behavior. In particular, both ANTs and ZNTs could exhibit significantly higher carrier mobilities compared to hexagonal monolayer and zinc-blende BSb, reaching 103-107 cm2 & sdot;V-1 & sdot;s-1. Our findings highlight strong curvature-induced modifications in the electronic properties of single-walled BSb nanotubes, demonstrating the latter as a promising candidate for high-performance electronic devices.

The cause of the anomalous shift in the first maximum peak of radial distribution functions (RDFs) with decreasing temperature in metallic melts and glasses remains highly controversial. In this study, we show that the first RDF peak exhibits anomalous expansion as the temperature decreases during the non-equilibrium solidification (γ1 = 1 × 1010 K s-1 and γ2 = 1 × 1011 K s-1) of liquid tantalum. This behavior is primarily due to alterations in both the geometric and electronic structures of the system. In terms of geometric structure, for example, at the cooling rate of γ1, the system forms a significant number of cage-like icositetrahedral Voronoi polyhedra (0,0,12,2) and standard icosahedral Voronoi polyhedra (0,0,12,0) at low temperatures. These Voronoi polyhedra have longer bond lengths and lower binding energies compared to their high-temperature counterparts. Furthermore, these Voronoi polyhedra nest together, forming a stable Ta26-C2v atomic configuration with minimal changes in bond lengths. This unique geometric arrangement contributes fundamentally to the anomalous expansion of the first peak of the RDF. Regarding the electronic structure, the temperature influences the interactions between Ta atoms. At higher temperatures, the electronic localization functions (ELFs) and the Mulliken bond overlap populations (Qi-j) are significantly increased, leading to stronger electronic interactions and a denser arrangement of nearest-neighbor atoms with shorter bond lengths. Consequently, the combined effects of geometric and electronic structural changes during non-equilibrium solidification could explain the anomalous expansion of the first peak of the RDF.

The linking chemistry between molecular catalysts and substrates is a crucial challenge for enhancing electrocatalytic performance. Herein, we elucidate the influence of various immobilization methods of amino-substituted Ni phthalocyanine catalysts on their electrocatalytic CO2 reduction reaction (eCO(2)RR) activity. A graphite-conjugated Ni phthalocyanine, Ni(NH2)(8)Pc-GC, demonstrates remarkable electrocatalytic performance both in H-type and flow cells. In situ infrared spectroscopy and theoretical calculations reveal that the graphite conjugation, through strong electronic coupling, increases the electron density of the active site, reduces the adsorption energy barrier of *COOH, and enhances the catalytic performance. As the cathode catalyst, Ni(NH2)(8)Pc-GC also displays remarkable charge-discharge cycle stability of over 50 hours in a Zn-CO2 battery. These findings underscore the significance of immobilization methods and highlight the potential for further advancements in eCO(2)RR.

AbstractTransition metal‐nitrogen‐carbon (M‐N‐C) catalysts have emerged as promising candidates for electrocatalytic CO2 reduction reaction (CO2RR) due to their uniform active sites and high atomic utilization rate. However, poor efficiency at low overpotentials and unclear reaction mechanisms limit the application of M‐N‐C catalysts. In this study, Fe‐N‐C catalysts are developed by incorporating S atoms onto ordered hierarchical porous carbon substrates with a molecular iron thiophenoporphyrin. The well‐prepared FeSNC catalyst exhibits superior CO2RR activity and stability, attributes to an optimized electronic environment, and enhances the adsorption of reaction intermediates. It displays the highest CO selectivity of 94.0% at −0.58 V (versus the reversible hydrogen electrode (RHE)) and achieves the highest partial current density of 13.64 mA cm−2 at −0.88 V. Furthermore, when employed as the cathode in a Zn‐CO2 battery, FeSNC achieves a high‐power density of 1.19 mW cm−2 and stable charge–discharge cycles. Density functional theory calculations demonstrate that the incorporation of S atoms into the hierarchical porous carbon substrate led to the iron center becoming more electron‐rich, consequently improving the adsorption of the crucial reaction intermediate *COOH. This study underscores the significance of hierarchical porous structures and heteroatom doping for advancing electrocatalytic CO2RR and energy storage technologies.

X-ray photoelectron spectroscopy (XPS) is a powerful characterization technique that unveils subtle chemical environment differences via core-electron binding energy (CEBE) analysis. We extend the development of real-space pseudopotential methods to calculating 1s, 2s, and 2p3/2 CEBEs of third-row elements (S, P, and Si) within the framework of Kohn-Sham density-functional theory (KS-DFT). The new approach systematically prevents variational collapse and simplifies core-excited orbital selection within dense energy level distributions. However, careful error cancellation analysis is required to achieve accuracy comparable to all-electron methods and experiments. Combined with real-space KS-DFT implementation, this development enables large-scale simulations with both Dirichlet boundary conditions and periodic boundary conditions.

The recently synthesized monolayer fullerene network in a quasi-hexagonal phase (qHP-C60) exhibits superior electron mobility and optoelectronic properties compared to molecular fullerene (C60), making it highly promising for a variety of applications. However, the microscopic carrier dynamics of qHP-C60 remain unclear, particularly in realistic environments, which are of significant importance for applications in optoelectronic devices. Unfortunately, traditional ab initio methods are prohibitive for capturing the real-time carrier dynamics of such large systems due to their high computational cost. In this work, we present the first real-time electron-nuclear dynamics study of qHP-C60 using velocity-gauge density functional tight binding, which enables us to perform several picoseconds of excited-state electron-nuclear dynamics simulations for nanoscale systems with periodic boundary conditions. When applied to C60, qHP-C60, and their solvated counterparts, we demonstrate that water/moisture significantly increases the electron-hole recombination time in C60 but has little impact on qHP-C60. Our excited-state electron-nuclear dynamics calculations show that qHP-C60 is extremely unique and enable exploration of time-resolved dynamics for understanding excited-state processes of large systems in complex, solvated environments.

Finite-temperature orbital-free density functional theory (FT-OFDFT) holds significant promise for simulating warm dense matter due to its favorable scaling with both system size and temperature. However, the lack of the numerically accurate and transferable noninteracting free energy functionals results in a limit on the application of FT-OFDFT for warm dense matter simulations. Here, a nonlocal free energy functional, named XWMF, was derived by line integrals for FT-OFDFT simulations. Particularly, a designed integral path, wherein the electronic density varies from uniform to inhomogeneous, was employed to accurately describe deviations in response behavior from the uniform electron gas. The XWMF has been benchmarked by a range of warm dense matter systems including the Si, Al, H, He, and H-He mixture. The simulated results demonstrate that FT-OFDFT within XWMF achieves remarkable performance for accuracy and numerical stability. It is worth noting that XWMF exhibits a low computational cost for large-scale ab initio simulations, offering exciting opportunities for the realistic simulations of warm dense matter systems covering a broad range of temperatures and pressures.

Orbital-free density functional theory (OFDFT) stands out as a many-body electronic structure approach with a low computational cost that scales linearly with system size, making it well suitable for large-scale simulations. The past decades have witnessed impressive progress in OFDFT, which opens a new avenue to capture the complexity of realistic systems (e.g., solids, liquids, and warm dense matters) and provide a complete description of some complicated physical phenomena under realistic conditions (e.g., dislocation mobility, ductile processes, and vacancy diffusion). In this review, we first present a concise summary of the major methodological advances in OFDFT, placing particular emphasis on kinetic energy density functional and the schemes to evaluate the electron-ion interaction energy. We then give a brief overview of the current status of OFDFT developments in finite-temperature and time-dependent regimes, as well as our developed OFDFT-based software package, named by ATLAS. Finally, we highlight perspectives for further development in this fascinating field, including the major outstanding issues to be solved and forthcoming opportunities to explore large-scale materials. This article is categorized under: Electronic Structure Theory > Density Functional Theory Software > Simulation Methods Quantum Computing > Theory Development

Finite-temperature orbital-free density functional theory (FT-OFDFT) holds significant promise for simulating warm dense matter due to its favorable scaling with both system size and temperature. However, the lack of the numerically accurate and transferable noninteracting free-energy functionals results in a limit on the application of FT-OFDFT for warm dense matter simulations. Here, a nonlocal free-energy functional, named XWMF, was derived by line integrals for FT-OFDFT simulations. Particularly, a designed integral path, wherein the electronic density varies from uniform to inhomogeneous, was employed to accurately describe deviations in response behavior from the uniform electron gas. The XWMF has been benchmarked by a range of warm dense matter systems, including the Si, Al, H, He, and H-He mixture. The simulated results demonstrate that FT-OFDFT within XWMF achieves remarkable performance for accuracy and numerical stability. It is worth noting that XWMF exhibits a low computational cost for large-scale ab initio simulations, offering exciting opportunities for the realistic simulations of warm dense matter systems covering a broad range of temperatures and pressures.

Due to the linear scaling of the computational cost with system size, orbital-free density functional theory (OF-DFT) offers a promising approach for large-scale materials simulations. However, the lack of high transferability local pseudopotentials in OF-DFT has impeded its wide use for materials simulations. Recently, the nonlocal pseudopotential energy density functional (NLPPF) method [Nat. Commun. 13, 1385 (2022)] has been proposed to enable OF-DFT to directly use nonlocal pseudopotentials and successfully applied to simple metallic systems formed by sp-block metallic elements. Here, we extend the NLPPF scheme for applications to the semiconducting systems by employment of the revised Huang-Carter kinetic-energy density functional. Applications of typical semiconductors including Si, Ge, and GaAs have systematically benchmarked the scheme. The results demonstrate that the NLPPF scheme combined with the revised Huang-Carter kinetic-energy density functional can significantly improve the accuracy of OF-DFT for simulating the semiconductors without extensive requirements of computational budget, which opens up new opportunities for OF-DFT applications to large-scale semiconducting systems.

In recent decades, the real-space finite-difference implementations of Kohn-Sham density functional theory have exhibited substantial improvements in computational efficiency for large-scale systems. However, the substantial memory consumption arising from the numerous grid points has begun to limit the widespread adoption of this method. In this study, a general method is presented-applicable to both periodic and Dirichlet boundary conditions-to reduce the number of real-space grids. This approach introduces a truncation of the real-space grids based on atomic positions, which reduces memory requirements and enables a more efficient real-space scheme tailored for simulating low-dimensional and porous materials with uneven spatial distributions. By testing the method on zero-dimensional clusters, one-dimensional tubes, two-dimensional clusters adsorbed on graphene, and three-dimensional metal-organic framework materials, a 30-73% reduction in grid points and a 36-71% reduction in computational time per step are observed for simulations with a 2 meV/atom energy difference.

We present a new velocity-gauge real-time, time-dependent density functional tight-binding (VG-rtTDDFTB) implementation in the open-source DFTB+ software package (https://dftbplus.org) for probing electronic excitations in large, condensed matter systems. Our VG-rtTDDFTB approach enables real-time electron dynamics simulations of large, periodic, condensed matter systems containing thousands of atoms with a favorable computational scaling as a function of system size. We provide computational details and benchmark calculations to demonstrate its accuracy and computational parallelizability on a variety of large material systems. As a representative example, we calculate laser-induced electron dynamics in a 512-atom amorphous silicon supercell to highlight the large periodic systems that can be examined with our implementation. Taken together, our VG-rtTDDFTB approach enables new electron dynamics simulations of complex systems that require large periodic supercells, such as crystal defects, complex surfaces, nanowires, and amorphous materials.

Interfaces, the boundary that separates two or more chemical compositions and/or phases of matter, alters basic chemical and physical properties including the thermodynamics of selectivity, transition states, and pathways of chemical reactions, nucleation events and phase growth, and kinetic barriers and mechanisms for mass transport and heat transport. While progress has been made in advancing more interface‐sensitive experimental approaches, their interpretation requires new theoretical methods and models that in turn can further elaborate on the microscopic physics that make interfacial chemistry so unique compared to the bulk phase. In this review, we describe some of the most recent theoretical efforts in modeling interfaces, and what has been learned about the transport and chemical transformations that occur at the air–liquid and solid–liquid interfaces.