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Ionic modulation of the charge transfer transitions in host–guest complexes of carbon nanorings and fullerenes
The hoop-shaped π-conjugated cycloparaphenylenes (CPPs), which constitute powerful hosts for complexation with fullerenes, were investigated by time-dependent density functional theory calculations and high-level second-order algebraic diagrammatic construction methods. For certain questions of open-shell character, complete active space self-consistent field and multireference ab initio calculations (strongly contracted N-electron valence state perturbation theory) have been performed as well. Host–guest complexes composed of [n]CPPs (n = 9, 10, 11) and pristine fullerenes (C60 and C70) were considered. Charge transfer (CT) processes between the fullerenes and the CPPs in ground state and excited states were the focus of this work. Our calculations clearly demonstrate the advantages of endohedral insertion of metal cations (Li+, Be2+, Na+, and Mg2+) into the fullerenes for tuning the CT states. The analysis of the pristine complexes shows the occurrence of local excitonic states on the CPP units as well as on the fullerenes. The latter represent the lowest excited states. Into these series on nonpolar states, CT states are embedded. Moving to the complexes with endohedral fullerene encapsulation leads to dramatic changes in the spectral composition. CT states are strongly stabilized and form extended bands of CT states that form the energetically lower end of the spectrum. Ionic modulation of CT states in these fullerene–CPP complexes offers a new insight for constructing photoactive supramolecular systems with efficient charge transfer between the donor and acceptor parts.
Three-dimensional pore collapse in shocked energetic crystals: Evaluating atomistics-consistent continuum models against molecular dynamics
The shock-induced collapse of three-dimensional (3D) pores in the energetic crystal RDX (1,3,5-trinitro-1,3,5-triazinane) is investigated using all-atom molecular dynamics (MD) and continuum simulations employing atomistics-consistent material models. We systematically investigate pore-collapse behavior by varying shock strengths and pore geometries, including spherical and ellipsoidal configurations. Transitions between strength (plasticity)-dominated and hydrodynamic collapse regimes are delineated, as well as the influence of pore orientation and length scale (nm to μm) on energy localization. By bridging atomistic and continuum descriptions, the study examines the role of three-dimensionality in hotspot formation and evaluates the accuracy of continuum predictions against MD benchmarks for inert pore collapse in RDX. We also evaluate atomistics-consistent material models for RDX, identifying aspects of pore collapse and hotspot formation that align with or deviate from MD. Differences between 3D and 2D pore collapse and hotspots are elucidated and aspects such as effects of crystalline anisotropy, orientation of elongated ellipsoidal pores, and pore size are assessed. This work points to avenues for further improvement of meso-scale models for predicting detonation initiation in RDX-based energetic materials in microstructure-aware multiscale frameworks.
Fluorescence microscopy imaging and molecular dynamics simulation studies on methylamphetamine solvation fluctuation disturbing lipid bilayer integrity and permeability
Methylamphetamine (METH) is a smaller neuronal stimulant molecule with a distinctive dipolar nature. This specific chemical structure enables it to interact and partition into both the hydrophobic and hydrophilic domains of the lipid bilayer through a process facilitated by its solvation thermodynamics in the surrounding environment of the cell membranes. Disruption of the lipid integrity at the molecular level arises from complex solvation dynamics of small drugs and alterations in the bilayer organization, which remain incompletely understood. These could be the likely underlying mechanism for METH’s permeating easily while clustering near headgroup levels inside the bilayer, interfering with the normal neuronal functions, such as forced release of neurotransmitters into the synaptic cleft and their abnormal accumulation in brain tissues. By integrating the fluorescence imaging assay techniques to detect the real time ion permeability and diffusion changes of the membrane with molecular dynamics simulations, we revealed that METH permeates readily and partitions preferentially into the lipid bilayer compared to the extracellular water level near the lipid bilayer headgroup interface, driving aggregations and assembling, causing disruptions that enhance the membrane fluidity and ion permeability, including increased calcium flux across lipid vesicles. These results provide a molecular-level insight into the mechanisms by which METH alters solvation dynamics and bilayer structure, highlighting how small amphipathic drugs compromise the membrane integrity and neuronal function, offering a framework for studying drug-induced perturbations of cell membrane integrity.
Pre-compensating curved electrode design for aberration reduction in modal control liquid crystal lenses
The nonlinear electro-optic response of liquid crystal materials poses a fundamental constraint for the performance of liquid crystal lenses. This work proposes a curved-bottom-electrode design for modal control liquid crystal lenses (MC-LCLs) to define the spacing between the high-resistance layer and the bottom electrode, thereby enabling the lens to generate a pre-compensated electric field. Through the nonlinear electro-optic response of the LC field to this pre-compensated electric field, the MC-LCL with a pre-compensating curved electrode (PCCE-MC-LCL) achieves quasi-parabolic optical path difference (OPD) profiles across the lens. Simulation results demonstrate that within the optical power range of 1.15–2.91 m−1, the PCCE-MC-LCL with a 5 mm aperture achieves an average RMS OPD error of 0.1115 λ, representing a significant 69.64% reduction compared with the conventional MC-LCL (0.3673 λ). The simulations further confirm that the curved electrode mitigates the degraded imaging performance of conventional MC-LCLs at high optical power, which originates from both their inherent lack of local electric-field modulation and the nonlinear electro-optic response of the LC.
CO2 dissociative sticking on Cu(110)
In this work, we perform quasi-classical trajectory calculations using an artificial neural network potential parameterized from ab initio calculations, to investigate the dynamics of CO2 interacting with Cu(110). The obtained dependencies of the molecular and dissociative adsorption probabilities on the initial translational energy of the molecules and surface temperature are in good (qualitative) agreement with available supersonic molecular beam experiments. We also investigate the influence of impact energy and surface temperature on the final state of the dissociation products, and we find that above ∼2.5 eV and close to or above room temperature, CO2 dissociation induces strong surface distortions, including final structures involving Cu adatoms. The creation of Cu vacancy–adatom pairs is stimulated by the presence of both COads and Oads, which interact strongly with the Cu adatoms and even give rise to unexpected (O–Cu–CO)ads linear moieties anchored to the surface by the dissociated O atom and involving a Cu adatom almost detached from the surface. These surface distortions produced by dissociation products of high-energy CO2 molecules at and above room temperature might explain recent experiments that have found saturation oxygen coverage for high energy molecules, larger than for slow molecules.
Symmetry-engineered band structure in two-dimensional multiferroic photonic crystals
In two-dimensional photonic crystals composed of the multiferroic terbium manganite (TbMnO3) crystal cylinders, we selected three-, four-, and six-fold spatial rotational symmetries to design the artificial lattice structure. Compared with two others, the six-fold symmetry opens and even widens the absolute bandgap in the far-infrared waveband at higher frequencies. When a static magnetic field is applied, it induces the broken time-reversal symmetry, which, in turn, arrows the bandgap. In all cases, the topological phase is robust. This symmetry engineering highlights an engineering strategy for photon-subclass far-infrared detectors, by magnetically manipulating the on-off state of absolute photonic bandgaps.
Quantum control of isotope-selective rotational contrast for H2O/T2O in the gas phase with nonresonant laser pulses
Isotope-selective rotational control of asymmetric-top molecules is a challenging task owing to their complex rotational dynamics. Here, we extend a simulation framework for isotope-selective rotational control to the water isotopologues H2O and T2O, and numerically identify pulse conditions that maximize isotope contrast in an equimolar gas-phase mixture driven by nonresonant, linearly polarized double pulses. We examine three characteristic rotational periods associated with ΔJ = 1 transitions from the ground state and find that TrotB+C=1/B+C provides the strongest synchronization for isotope contrast. To quantify isotope-selective rotational contrast, we define a rotational contrast metric based on the three-dimensional alignments of H2O and T2O. When the pulse delay is synchronized to TrotB+C, the metric reaches a maximum value of 1.99 at 10 K; further optimization of the pulse delay and intensity ratio increases the metric to 2.20. These results demonstrate that appreciable isotope-selective contrast can be achieved even in the H2O/T2O system, where the small polarizability anisotropy makes alignment control inherently difficult, and establish a versatile route toward isotope-selective rotational control of more complex asymmetric-top molecules.
Research on the generation mechanism of CO in low-pressure CO2 dielectric barrier discharge driven by microsecond pulse voltage
The conversion of Martian atmospheric CO2 to CO, a key propellant and organic precursor, is crucial for in situ resource utilization. Addressing CO2's high stability, this study employs a repetitive microsecond-pulsed dielectric barrier discharge to drive glow plasma for CO2-to-CO conversion. Experiments and numerical simulations reveal the kinetic mechanism of CO generation at 1 kPa. A maximum CO2 conversion rate of 31.2% is achieved under microsecond-pulse driving. Strong 483 nm emission, attributed to CO(B1Σ+–A1Π), is observed ∼0.5 mm from the instantaneous cathode (cathode fall boundary) during both discharge phases. The emission intensity is higher in the positive discharge phase, correlating with its larger discharge power. Quantitative analysis attributes 44.8% and 29.8% of CO generation to the positive and negative discharge phases, respectively. The process is dominated by electron-impact dissociation reaction (E26: e + CO2 → e + CO + O), contributing ∼90% of the CO yield. The spatiotemporal distribution of the E26 reaction rate coincides with the ionization wavefront and high-electron-temperature region, explaining the CO creation pattern. This work elucidates the dynamic coupling between discharge evolution and CO production, providing insights for plasma reactor design.
First-principles computation of electronic circular dichroism spectra of solvated molecules using RISM-SCF-cSED
We propose a practical first-principles protocol for computing electronic circular dichroism (ECD) spectra of chiral molecules in aqueous solution by combining time-dependent density functional theory (TDDFT) with the reference interaction site model self-consistent field with constrained spatial electron density (RISM-SCF-cSED), and, when necessary, molecular dynamics-based conformational sampling. After demonstrating the approach for D-lactic acid in water as a benchmark system with limited conformational variability, we apply a similar workflow to a solvated biomolecule, the terminally capped alanine tetramer (Ac-Ala4-NMe). One of the achievements of this study is that incorporating an explicit solute water hydrogen-bonding structure through RISM-SCF-cSED enables quantitative reproduction of the ECD spectrum of the rigid α-helical state. These results establish RISM-SCF-cSED/TDDFT combined as a general and computationally efficient platform for predicting ECD spectra of solvated molecules.
Enhanced bandwidth performance in Michelson interferometer modulator via a combination of micro-structured electrodes and Bragg grating reflector
The Michelson interferometer (MI) modulator is a folded-type modulator with significantly reduced dimensions because of the doubled effective interaction length between the transmitted light and modulation signal. However, the folded structure also exacerbates the velocity mismatch, which limits the bandwidth of the MI modulators. In addition, the relatively large footprint of the reflector also hinders further miniaturization of MI modulators. Herein, we propose a new type of modulator that incorporates both a microstructured electrode and a Bragg grating reflector. Based on the thin-film lithium niobate (TFLN) platform, the proposed MI modulator was successfully fabricated. Owing to the application of microstructured electrodes, the microwave loss is reduced to only 1 dB/cm at 50 GHz, indicating an enhanced modulation bandwidth. Meanwhile, the footprint of the reflection region was reduced to 36 μm using a Bragg grating reflector, which is one-tenth that of the loop mirror. Finally, the proposed MI modulator demonstrates a high 3 dB bandwidth (beyond 60 GHz), a low half-wave length product (1.45 V cm), and a significantly enhanced voltage-bandwidth performance (approximately 2.58 GHz V−1), indicating a great potential for applications in future optical interconnection modules, where lower microwave loss and higher integration are urgently needed.
Finite-size effects and energy alignment in molecular XANES under periodic boundary conditions: A systematic comparison of core-hole treatments
X-ray absorption near-edge structure (XANES) provides element-specific insights into local electronic and structural environments, but quantitative interpretation of molecular XANES under periodic boundary conditions (PBC) remains challenging due to finite-size effects and core-hole treatments. In this work, we systematically investigate how core-hole approximations and charge compensation schemes affect transition energies, energy alignment, and chemical-shift reproducibility in PBC-density functional theory-based molecular XANES calculations. Using ethane as a model system, we show that the full core-hole (FCH) approach exhibits a pronounced supercell-size dependence originating from interactions between background charge and charged molecules, with transition energies largely changed by leading-order finite-size terms. In contrast, the excited core-hole (XCH) method rapidly converges owing to its neutral final state. We further demonstrate that most finite-size effects in FCH can be removed by Makov–Payne corrections based on multipole expansion of the electrostatic energy of charged supercells under PBC. Furthermore, we propose a simple Fermi-level-based energy correction (EF/2) that provides comparable improvement using only a single supercell. Extending the analysis to an n-alkane series reveals that while intrinsic electronic-structure changes govern peak shifts for small molecules, systematic energy drifts persist in FCH for larger molecules, whereas XCH and FCH + EF/2 remain stable. Finally, for small molecules at the C and N K-edges, XCH and FCH + EF/2 accurately reproduce experimental chemical shifts, whereas uncorrected FCH fails. These results provide practical guidelines for reliable energy alignment and chemical-shift analysis in molecular XANES under PBC, supporting robust applications to molecular, adsorption, and interfacial systems.
Controlling the paramagnetic-defects response in mixed-phase layered MoS2 nanosheets with light
The paramagnetic response of mixed-phase (1T/2H) layered MoS2 nanosheets’ powder is investigated by means of electron paramagnetic resonance (EPR) in pulse and continuous regime at low temperatures (from 8 to 60 K), with external laser optical excitations. Under dark condition, the sample exhibits two distinct 1/2 spin signals corresponding to different point defects within the semiconducting phase (2H) of MoS2 layers. Spin-echo detection of the two signals demonstrates their potential use for quantum processing at low temperature. Under illumination by optical laser beams, both EPR signal intensities are substantially and simultaneously reduced in a reversible and almost instantaneous manner. The proportion of signals extinction is found to depend on the optical power P and temperature T, while being independent of the optical wavelength remaining above the electronic bandgap, from 405 to 785 nm. The fitting of EPR intensities as functions of P and T based on a simple excitation/relaxation model leads to the prediction of an almost complete and reversible signals extinction at T = 4 K and P = 324 mW, leading to a potential fully optically controlled spin switch. Investigation of the commutation time between dark and illuminated states shows that the mixed-phase (1T/2H) sample displays faster dynamics, as compared to single-phase (2H) samples.
<i>GW</i> -BSE for molecular excited states in REST: State-of-the-art methods, acceleration strategies, and the LAMB approximation
We present a comprehensive implementation of the GW-BSE approach for molecular excited states within the Rust-based electronic structure toolkit. Utilizing the resolution-of-identity approximation and contour deformation technique, our implementation achieves both numerical robustness and computational efficiency. The module encompasses a hierarchy of established GW variants, including one-shot G0W0, eigenvalue-self-consistent evGW, and the cost-effective renormalized singles rsGW, followed by full or Tamm–Dancoff approximation BSE calculations. As an original methodological contribution, we introduce the low angular momentum basis approximation for BSE, which systematically truncates the auxiliary basis to reduce computational cost while preserving accuracy. Validation against MolGW confirms meV-level agreement for both quasiparticle and excitation energies. Benchmarking on the GW100 set demonstrates that rsGW achieves a mean absolute error of 376 meV for quasiparticle HOMO energies, substantially improving upon G0W0. To address the computational demands of GW-BSE, we propose and systematically evaluate three acceleration strategies: (i) a GW extrapolation scheme that reduces explicit quasiparticle calculations by an order of magnitude while maintaining chemical accuracy (errors below 43 meV); (ii) a virtual orbital cutoff that delivers a 9× speedup for a 94-atom Au(III) complex with minimal errors (10 meV); and (iii) the LAMB-BSE approximation, which achieves 1.5× acceleration while confirming the essential role of d-type functions, with deviations below 20 meV for both singlets and triplets. All functionalities presented in this study have been made publicly available in the REST open-source repository (https://gitee.com/restgroup), accompanied by detailed documentation and usage examples to facilitate community adoption. Together, these methodological developments establish the GW-BSE implementation in REST as an efficient and reliable tool for excited-state studies and provide practical guidelines for balancing accuracy and efficiency in molecular GW-BSE calculations.
Monte Carlo calculation of electron backscattering coefficients for Fe and Ni solids
We have calculated the electron backscattering coefficients η(Ep) for elemental solids, Fe and Ni, for primary electron energies of 0.1–100 keV, by utilizing a state-of-the-art Monte Carlo simulation model. A relativistic dielectric functional approach was applied to calculate the electron inelastic cross section, incorporating various data sets of the optical energy loss function (ELF). The calculation results reveal that the backscattering coefficient is profoundly affected by the ELF, conforming to the f-sum and ps-sum rules. To evaluate uncertainties in relation to experimental data, we examined the systematic errors related to contaminated surfaces. Simulations of Fe and Ni surfaces contaminated with carbonaceous atomic layers successfully accounted for the trend of the observed experimental data. Our findings indicate that precise backscattering coefficient value should either be measured from thoroughly cleaned surfaces or calculated from the Monte Carlo simulation that utilize reliable optical constant data. These simulation data have worth in multiple scientific fields particularly for the application of scanning electron microscopy. Given recent advancements in the accurate measurement of optical constants through reflection electron energy loss spectroscopy, there is considerable promise for developing a robust theoretical database of electron backscattering coefficients for the clean surfaces of elemental solids.
Cryogenic photoelectron and photodetachment spectroscopy of complex anions
While supersonic cooling revolutionized spectroscopic studies of neutral molecules, cooling molecular ions remains far more challenging, especially for ions generated from electrospray ionization (ESI). Cryogenic cooling has been transformative, particularly for ESI-produced ions, by enabling intrinsically cold spectroscopic interrogation of solution-phase species transferred into the gas phase. This perspective focuses on cryogenic photoelectron spectroscopy (PES) and photodetachment spectroscopy (PDS) of complex anions produced by ESI and cooled in a 3D Paul trap, a platform that has been widely adopted because of its relative simplicity and robust performance. We discuss the technical evolution from the initial ESI-PES for solution species to cryogenic ESI-PES with a magnetic-bottle analyzer, and the current cryogenic PDS and high-resolution photoelectron imaging. We emphasize significant advances enabled by coupling the cryogenic 3D Paul trap first to ESI sources—highlighting studies of temperature-dependent phenomena, solution-phase chemistry in the gas phase, nonvalence excited states, vibrationally induced autodetachment, and resonant PES—and more recently to a laser-vaporization cluster source, demonstrating more effective vibrational cooling for cluster ions than supersonic expansion.
Axial and shear stress in nitrogen-doped homo-epitaxial chemical-vapor-deposition diamond films
Control of residual stress in diamond is crucial to improve the spin dephasing time (T2*) of nitrogen-vacancy centers for quantum applications. When the surface of a substrate used for homoepitaxial growth is crystallographically tilted at a slight angle away from a major crystal plane [e.g., (001)], the atomic structure of the surface at the homoepitaxial growth front changes, which in turn alters the homoepitaxial growth mode. As a result, the incorporated stress in the homoepitaxial diamond layer is also likely to vary. In this study, we investigated the effect of the substrate inclination-direction in the (001) plane, the so-called inclination-direction, on the residual stresses. The 400 μm-thick nitrogen-doped (001) diamond films were grown on the substrates with different inclination-directions, a [110] or a [100]. Mapping of the stress tensor revealed that the inclination-direction alters the nature of the residual stress: the [110] inclination-direction led to a dominant gradient in the axial stress (σxx + σyy + σzz) along the [001] direction, whereas the [100] inclination-direction led in shear stress (σxy, σyz, and σzx). Although the nature of the residual stress changed with the inclination-direction, the mean values of the measured T2* were comparable for both samples (1.25 μs for [110] and 1.26 μs for [100]). This result was consistent with the fact that the dephasing rate due to the stress in the CVD diamond film (0.25 MHz for [110] and 0.26 MHz for [100]) was comparable.
Velocity formulations for hyper-Rayleigh scattering optical activity spectroscopy: Addressing the origin-dependence problem
The theory of hyper-Rayleigh scattering optical activity (HRS-OA) spectroscopy has previously been described within the length formulation of the pure electric-dipole and mixed (electric-dipole/magnetic-dipole and electric-dipole/electric-quadrupole) first hyperpolarizabilities required for the description of this process. In this study, we provide an alternative formulation of these pure and mixed hyperpolarizabilities. This new formulation made use of the velocity form of the electric-dipole and electric-quadrupole moment operators that enter into the quadratic response functions. A one-to-one correspondence is found for the gauge-origin shifts obtained in the two formulations. These relations ensure the origin-independence of the theory also for the velocity formulation. Furthermore, even though the basis set dependence of the velocity formulation is more significant compared to the length one, the former is origin-independent by design. This property makes it particularly suitable for calculations of HRS-OA invariants using approximated (variational or not) wave functions.
Thermomagnetic instability of type-II superconducting bulks with pores based on fractal theory
The magnetic flux jump phenomenon induced by thermal disturbance easily occurs in the magnetization process of type-II superconducting bulk materials, which seriously affects their macroscopic electromagnetic properties and application stability. Traditional research studies assume that materials are homogeneous and dense, ignoring the influence of the complex pore structure formed in the actual preparation process on magnetocaloric behavior. In this paper, based on the fractal theory, we establish a magnetic–thermal coupling model considering a complex pore structure to study the thermomagnetic instability of BiSrCaCuO bulk samples under different magnetization processes. The effects of fractal dimension, iteration times, porosity and magnetization mode (zero-field cooling and field cooling) on magnetization curve, temperature evolution and flux jump behavior are studied. The results show that the pore structure significantly affects the effective specific heat and the induced current of superconductors, and changes the frequency and initial field of magnetic flux jump. When the porosity exceeds a certain threshold, the Joule heat decreases significantly and the magnetic flux jump disappears. Different fractal structures exhibit similar magnetization correspondence at the same volume fraction, which proves that volume fraction is a key variable affecting magnetization behavior. In addition, the effects of the parameters such as sample size, ambient temperature, and external magnetic field sweep rate on magnetocaloric behavior are also discussed. This study provides a new theoretical method for understanding and optimizing the thermomagnetic stability of porous superconducting materials.
Eliminating delocalization error through localized orbital scaling correction with orbital relaxation from linear response
Despite the great success that Kohn–Sham density functional theory (KS-DFT) has achieved, the delocalization error remains a major challenge for commonly used density functional approximations, resulting in systematic errors in ionization energies, electron affinities, band structures, and charge distributions. A recently developed localized orbital scaling correction (LOSC) method, namely, linear response LOSC (lrLOSC), addresses these challenges by incorporating a functional correction that includes the screening effect and orbital localization within the LOSC framework. The method has been shown to provide accurate descriptions of bulk systems and core-level binding energies in small molecular systems. In this work, we extend the applicability of lrLOSC to a broader range of molecular systems, spanning various sizes, with a focus on the corrections to valence orbital energies and total energies. To enable the calculation of large chemical systems, we developed an efficient implementation of lrLOSC with computational costs comparable with standard KS-DFT calculations. Numerical results show that while screening provides modest improvements for small molecules, it becomes critical for achieving high accuracy in larger molecules, from linear to three-dimensional systems. With the screening effect being well captured in a unified way, lrLOSC provides accurate descriptions for a wide range of chemical systems, including organic molecular systems of varying sizes and transition-metal oxide complexes, establishing it as a powerful tool for enhancing the reliability of computational simulations of chemical systems.
Effect of external circuit on the self-bias of capacitively coupled plasma driven by tailored voltage waveforms
In this work, the influences of the direct current blocking capacitor, stray capacitance, and stray resistance in the external circuit on the self-bias driven by tailored voltage waveform (TVW)-driven asymmetric capacitive discharges are investigated using a one-dimensional three-velocity particle-in-cell/Monte Carlo collision model coupled with an external circuit. Under a zero-initial-phase sinusoidal TVW drive with an amplitude ratio of 3:2:1, a dc self-bias voltage is generated and can be significantly modulated by the blocking capacitor, stray resistance, and stray capacitance. The approximate adjustment ranges of each external circuit parameter, as well as an optimized combination of circuit parameters under specific discharge conditions are presented. Based on bias control using a single external component, combined control of multiple external circuit parameters enables a wider tuning range of plasma density, ion flux, and ion energy at the boundary. In addition, the mechanisms responsible for the formation of positive and negative self-bias voltages at different pressures are discussed. These results may provide insight and a theoretical reference for the engineering design of bias control in electrical asymmetric capacitively coupled plasma systems.