Abstract Dynamic fracture (spallation) in metals under high strain-rate loading is critical in impact and shock environments. We present a multiscale modeling framework to predict the spall strength of single-crystal iron by integrating atomistic-scale void evolution with continuum hydrodynamics. Molecular dynamics simulations are performed to simulate the tension along <100>, <110>, and <111> directions under multiaxial loading conditions, and the fracture parameters are extracted via a void-volume-based optimization strategy. These atomistically derived parameters are integrated into hydrodynamic models through an Average Void Growth in Fluid Element homogenization scheme, enabling accurate representation of atomic-scale mechanisms at the macroscopic level. The resulting model reproduces key free surface velocity features and closely matches the experimental power law σ = 0.0835 • ε0.2942 with an RMS error of 0.27 GPA. This approach offers a rigorous and transferable description of dynamic fracture under extreme conditions.

Abstract Transient grating spectroscopy (TGS) is a material characterization technique based on laser-induced thermoelastic excitation of thermal and acoustic gratings. On opaque samples, these gratings are dynamic surface displacements that reflect the sample’s elastic and thermal properties, enabling both types of parameters to be determined from a single experiment. Here, we develop a detailed finite element model (FEM) of the TGS experiment that fully captures the coupling between the thermal and mechanical fields, as well as the optical detection of surface displacement using a heterodyning approach. Using custom-designed two-dimensional elements, the model is particularly suitable for analyzing TGS measurements on anisotropic media, for which analytical theory is insufficient. The simulation captures not only the anisotropic relaxation of the thermoelastic field but also several acoustic features that arise at very short (ultra-transient) timescales and provide additional information about the elastic properties of the examined material. The model offers new opportunities for the in silico testing of various modifications of TGS experiments and their applications to a broad class of materials.

Abstract A comprehensive first-principles investigation of the structural, electronic, and optical properties of the 2D Cu 2 WSe 4 slab is presented using three-dimensional density functional theory calculations as implemented in the SIESTA code. The optimized crystal structure is analysed in terms of its electronic band structure and orbital-resolved density of states, revealing an indirect band gap with the valence-band maximum along the M –Γ direction and the conduction-band minimum located at the Γ point. Detailed crystal orbital overlap population/crystal orbital Hamiltonian population analysis is employed to elucidate the nature of Cu–Se and W–Se bonding interactions and their influence on the formation of valence and conduction states. Optical properties are examined within the independent-particle approximation, where the absence of low-energy absorption is shown to originate from the indirect nature of the band gap, while prominent absorption features at higher photon energies arise from direct interband transitions involving Se- p and W- d states. By correlating electronic structure, chemical bonding, and optical response, this work provides a unified microscopic understanding of the optical behaviour of Cu 2 WSe 4 and highlights the importance of bonding-driven electronic transitions beyond simple band-gap considerations. The present results offer valuable insight for the rational design and optimization of Cu-based chalcogenide materials for optoelectronic and photovoltaic applications.

Abstract CCu is a common alloying element in medium and high-entropy alloys (M/HEAs), and its tendency to segregate over time has a notable impact on their properties. In this study, we investigate the effect of Cu segregation on evolution of irradiation-induced defects in FeNiCu, a model MEA, using hybrid molecular dynamics (MD) and Monte Carlo (MC) simulations. Thermodynamically driven hybrid MC/MD annealing at low temperature resulted in a partially decomposed Cu-segregated structure (CSS) and was compared with a random solid solution (RSS) and pure Ni. Results through cumulative displacement cascades reveal that Cu-rich domains in CSS act as defect traps, accelerating point defect recombination and suppressing defect cluster growth. The complex potential energy landscape (PEL) in CSS disrupts dislocation propagation, leading to spatially dispersed networks. Notably, CSS exhibits reduced stair-rod dislocation density compared to RSS, highlighting its superior resistance to irradiation swelling under the simulated high-dose-rate conditions. Localized shear strain causes dislocations to preferentially nucleate in/near Cu-rich regions though their growth is hindered by chemical heterogeneity of the alloy. Notably, prolonged irradiation induces slow Cu segregation in the RSS structure, while slowly annihilating pre-existing Cu clusters in CSS simultaneously. These findings provide atomic-scale insight into the interplay between Cu segregation and irradiation-induced defect evolution in MEAs, with implications for the design of radiation-tolerant structural materials in nuclear and fusion energy systems.

Abstract The elastic tensor provides valuable insight into the mechanical behavior of a material with lattice strain, such as disordered binary alloys. Traditional stress–strain methods have made it possible to compute elastic constants for high-throughput databases of ordered structures, as well as individually tailored alloy compositions. However, this approach depends on predetermined or iteratively-chosen strain tensors. This poses a significant challenge for systematic, composition-dependent studies of disordered materials requiring structural models with randomized atomic positions and possessing low symmetry. Density functional perturbation theory (DFPT) based on density functional theory provides a compelling alternative to stress–strain methods: it allows for an unbiased determination of the elastic tensor, as well as access to local field data derived from the underlying general response function framework. Despite its intrinsic flexibility and efficiency, DFPT has seen limited application to the study of disordered systems. At the same time, there is a growing need for expanded quantum mechanical data to improve predictive modeling of complex disordered material properties. Here we present results for the rigid-ion and relaxed-ion elastic tensors computed using DFPT, for a comprehensive set of disordered structural refractory body-centered cubic binary alloys of molybdenum (Mo), niobium (Nb), tantalum (Ta), and tungsten (W). For the first time, we have mapped the quantum-driven heterogeneity in elastic constants and derived mechanical properties—bulk modulus ( B ), shear modulus ( G ), Young’s modulus ( E ), and Poisson’s ratio ( ν )—and associated nuclear-relaxation fields at each disordered structure lattice site. The derived properties, together with Pugh’s ratio ( B / G ), Cauchy pressure and elastic anisotropy, are reported as a function of composition for all refractory binaries. The DFPT-computed elastic constant results for the refractory binary alloys at systematically-varied Mo, Nb, Ta, and W compositions are in excellent agreement with available experimental data.

Abstract Highly regular porous armchair graphene nanoribbons having a width of 12 atoms were synthesized recently. A model for investigating the quantum transport properties in such nanoribbons is developed by using a tight-binding lattice. The mode propagation in the nanoribbons is examined by analyzing the equations of motion. The lattice-Green-function technique is employed in calculating the quantum transmission coefficients of the Bloch modes. The calculation method of the lattice Green functions is adjusted to be suitable for the porous geometry of the nanoribbons for the situations where the conventional method is inapplicable due to the presence of the pores. The quantum transport exhibits a Fabry–Pérot interference when the porous nanoribbon is sandwiched by pristine nanoribbons. The lower envelop of the interference oscillation agrees with the prediction derived from the scattering properties at a single porous-pristine junction in the single-mode transport regime. While the oscillation envelop cannot be predicted in general in the multi-mode transport regime due to the random superposition of the oscillation components associated with the individual modes, the transmission is found to become even less than the predicted lower bound occasionally. In addition, the modes are not always independent from each other in the superposition. The comparison of the envelop form is made also for the quantum interference properties in a porous-pristine-porous junction. The violation of the lower bound is extensive including the single-mode regime when the coexisting Fano resonance states appear to fuse with the Fabry–Pérot interference states.

Abstract This study presents an integrated phase field-crystal plasticity modeling framework for predicting the microstructure evolution during aging heat treatment and the subsequent mechanical properties for single crystal Ni-based superalloys. The phase field model, based on the Kim-Kim-Suzuki model, accounts for the anisotropic growth and coarsening of precipitates during aging. Specifically, the interfacial anisotropy in the phase field model is used to simulate the morphological evolution of precipitates from an initial spherical/circular shape to a cuboidal/square shape, which is a characteristic feature of the γ ′ precipitate growth in superalloys. Application of the model has been demonstrated in the form of three different case studies. The first case study simulates the two stage aging of a commercial single crystal superalloy, CMSX-4, followed by the prediction of the temperature-dependent tensioncompression asymmetry of the aged microstructures. These results highlight the capability of the model to predict processing-microstructure-mechanical property correlations. The second case study simulates the microstructure evolution during long-term aging of CMSX-4 for relatively larger microstructures, highlighting the capability of the model to predict precipitate coarsening. Further, the effect of varying the cooling rate on the microstructure evolution is also demonstrated. The third case study simulates the microstructure evolution during aging at relatively lower temperatures for Ni-Al alloys with different compositions. These results highlight the capability of the model to predict the change in precipitate morphology from circular to square shape during the initial stages of aging. Model predictions of the precipitate size, volume fraction and mechanical properties have been compared with relevant literature data. Overall, this integrated phase field-crystal plasticity framework offers a powerful tool for the computational design of single crystal superalloys.

Abstract In the context of the development of solar photovoltaics for global energy production, it remains essential to clearly identify performance limitations. The present article revisits the interpretations of photovoltaic cell performance by introducing a path-integral formulation of the current. The case of a single p–n junction cell operating in low injection conditions is examined as a proof of concept. The total current is calculated by implementing two different algorithms, which exhibit two viewpoints for analyzing the physics involved. The first one describes random walks on a reverse path space, back to the source of charge carriers. The second one describes random walks on a direct path space, starting from the source. Both algorithms are validated against an analytical solution. A Monte Carlo (MC) algorithm is also proposed for directly determining the voltage at the maximum power point without requiring the entire current–voltage curve. The calculation of a spectral-spatial internal quantum efficiency, combined with a statistical analysis of the random paths, demonstrates the relevance of this approach for interpreting the involved physics. Numerous benefits are anticipated from our advancements in MC techniques: enhanced physics representations, insensitivity of computation time to the dimension of the integration domain, and to the geometrical complexity at all scales.

Abstract This study employs atomistic molecular dynamics simulations to investigate the anisotropic mechanical behavior of pristine and vacancy-induced Nb2C MXene under varying temperatures (300–1500 K), strain rates (0.003–0.025 ps−1), and point vacancy concentrations (1%–5%). Using a modified embedded-atom method potential, the study reveals significant directional dependence in elastic modulus and tensile strength, with the [100] direction exhibiting a Young’s modulus of 282.54 GPa and tensile strength of 23.10 GPa—both substantially higher than in the [010] direction. This indicates that the tensile strength along the [100] direction is 35.36% higher than the [010] direction, suggesting an anisotropic mechanical behavior. The mechanical performance degrades with increasing temperature, as evidenced by reductions in Young’s modulus and ultimate tensile strength, supported by partial radial distribution function analysis. Furthermore, higher strain rates enhance tensile strength, indicating strain-rate sensitivity. The introduction of Nb and C point vacancies significantly diminishes mechanical integrity, with effects more pronounced under elevated thermal conditions. These findings provide critical insights into the mechanical resilience and design considerations of Nb2C-based nanodevices for applications in energy storage, flexible electronics, and sensing platforms.