The fracture response of body-centered-cubic tungsten is governed by competition between crack-tip instability and dislocation-mediated plastic accommodation. Molecular dynamics (MD) simulations are used to examine edge-cracked polycrystalline W and W-Re under displacement-controlled Mode-I tension from 300-1800 K at a strain rate of 5 x 10^8 s^-1. Heating pure W reduces the instability stress, effective specimen stiffness, and pre-instability volumetric work density, while the instability strain remains comparatively scattered. A normalized work-loss metric derived from the pre-instability work gives a broad sigmoid crossover marker, T*_MD ~ 870 K, characteristic of the simulated geometry and high-rate loading conditions. Among the available W-Re compositions, W-10Re shows greater pre-instability deformation and work accumulation than pure W across most temperatures, while the maximum-stress response remains strongly temperature- and composition-dependent. Changes in retained dislocation character and near-tip activity indicate that Re modifies the crack-tip plastic-accommodation pathway rather than producing a simple strength increase. Common-state analysis further shows that Re alters the retained 1/2<111>line character and the temporal distribution of near-tip dislocation activity without uniformly increasing the local dislocation population. These coupled mechanical and defect-structure changes provide atomistic indicators of a high-rate ductile-to-brittle transition (DBT), but not a direct prediction of experimental DBTT. A separate OpenDiS/pydis calculation demonstrates source-like bow-out and heterogeneous dislocation-network development in crack-free polycrystalline W, providing mesoscale context without implying direct quantitative MD-DDD coupling.
: Semiconductor quantum dot platforms require rapid recognition of charge states during automated device tuning, especially when labeled data are scarce and device-to-device variation is strong. This study evaluated state recognition from 100 by 100 two-gate current maps using 30 by 30 labeled patches under a strict device-level split. Patch features were transformed with a signed logarithmic scale, standardized, compressed to four principal components, and scaled to the interval from zero to two pi. A fidelity quantum kernel support vector machine implemented in IBM Qiskit with a four-qubit ZZFeatureMap was compared against linear and radial basis function support vector machines across few-shot budgets of 10, 20, 40, and 80 samples per class. At 80 samples per class, the quantum kernel model achieved accuracy and macro F1 near 0.947 on held-out devices, outperforming the classical baselines in the evaluated setting. Noise-injection experiments showed stable macro F1 under perturbation. These findings support fidelity-based quantum kernels as practical components for automated quantum dot tuning pipelines requiring few-shot generalization.
M. Ashakin, Rubayat Khan, A. Mahata et al.· Proceedings of the 15th Inte...· 0 citations
Controlling elemental mixing in nanoparticles composed of immiscible elements remains a central challenge in high-entropy materials design. Here, we demonstrate a kinetic pathway that enables a transition from elementally segregated to high-entropy AgNiCoCr nanoparticles using nanosecond laser-induced dewetting of metallic thin films. During this nonequilibrium process, nanoparticles form through a sequence of morphological transformations and ultimately evolve into near-spherical structures with thickness-dependent sizes. In the chosen model system, Ag is thermodynamically immiscible with Ni and Co, whereas Ni, Co, and Cr are mutually miscible at equiatomic compositions. By varying the thickness and configuration of the metallic thin-film layers, the liquid-phase lifetime during laser irradiation is systematically tuned, thereby regulating mass transport and solidification dynamics. Ultrathin film stacks produce smaller nanoparticles (up to ∼40 nm) that rapidly solidify on nanosecond time scales, kinetically trapping metal atoms into a chemically disordered high-entropy phase. In contrast, thicker films remain molten for longer durations during dewetting, leading to the formation of larger nanoparticles with pronounced elemental segregation into AgNiCoCr core–shell or Janus structures. Supported by atomistic simulations, this work demonstrates that solidification kinetics, rather than thermodynamic immiscibility, governs chemical order in laser-processed nanoparticles, providing a versatile strategy for engineering high-entropy nanoparticles from immiscible elements.
Soumya Mandal, A. Mahata, Annaliese Colwell et al.· ACS Applied Nano Materials· 0 citations
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