- 标题
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- 实验方案
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The effect of grain-size on fracture of polycrystalline silicon carbide: A multiscale analysis using a molecular dynamics-peridynamics framework
摘要： A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructure-property-performance interplay in solid-state materials.
关键词： Peridynamics,Polycrystalline,Multiscale modeling,3C-SiC,Grain boundaries,Molecular dynamics
更新于2025-09-23 15:22:29
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Run-to-run control of PECVD systems: Application to a multiscale three-dimensional CFD model of silicon thin film deposition
摘要： Deposition of amorphous silicon thin films via plasma-enhanced chemical vapor deposition (PECVD) and batch-to-batch operation under run-to-run control of the associated chambered reactor are presented in this work using a recently developed multiscale, three-dimensional in space, computational fluid dynamics model. Macroscopic reactor scale behaviors are linked to the microscopic growth of amorphous silicon thin films using a dynamic boundary which is updated at each time step of the transient in-batch simulations. This novel workflow is distributed across 64 parallel computation nodes in order to reduce the significant computational demands of batch-to-batch operation and to allow for the application and evaluation in both radial and azimuthal directions across the wafer of a benchmark, run-to-run based control strategy. Using 10 successive batch deposition cycles, the exponentially weighted moving average algorithm, an industrial standard, is demonstrated to drive all wafer regions to within 1% of the desired thickness set-point in both radial and azimuthal directions across the wafer surface. This is the first demonstration of run-to-run control in reducing azimuthal film nonuniformity. Additionally, thin film uniformity is shown to be improved for poorly optimized PECVD geometries by manipulating the substrate temperature alone, without the need for re-tooling of the equipment.
关键词： thin film silicon solar cells,parallel computing,multiscale modeling,computational fluid dynamics,run-to-run control,thin film growth
更新于2025-09-23 15:21:21
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Multiscale Simulation of Photoluminescence Quenching in Phosphorescent OLED Materials
摘要： A multiscale simulation protocol to treat triplet–triplet annihilation (TTA) in phosphorescent organic light-emitting diodes (PhOLEDs), in which microscopic parameters are computed with ab initio electronic structure methods, is presented. Virtual photoluminescence experiments are performed on a prototypical PhOLED emission material consisting of 4,4?,4?-tris(N-carbazolyl)triphenylamine and fac-tris(2-phenylpyridine)iridium. The obtained TTA quenching rate is comparable to experimental results in the low-intensity limit.
关键词： multiscale modeling,organic light-emitting diodes,exciton quenching,triplet–triplet annihilation
更新于2025-09-23 15:19:57
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A multiscale materials-to-systems modeling of polycrystalline PbSe photodetectors
摘要： We present a physics based multiscale materials-to-systems model for polycrystalline PbSe photodetectors that connects fundamental material properties to circuit level performance metrics. From experimentally observed ?lm structures and electrical characterization, we ?rst develop a band structure model that explains carrier-type inversion and large carrier lifetimes in sensitized ?lms. The unique band structure of the photosensitive ?lm causes separation of generated carriers with holes migrating to the inverted PbSejPbI2 interface, while electrons are trapped in the bulk of the ?lm intergrain regions. These ?ows together form the 2-current theory of photoconduction that quantitatively captures the I(cid:2)V relationship in these ?lms. To capture the e?ect of pixel scaling and trapped carrier blocking, we develop a model for the metallic contacts with the detector ?lms based on the relative workfunction di?erences. We also develop detailed models for various physical parameters such as mobility, lifetime, quantum e?ciency, noise, etc. that connect the detector performance metrics such as responsivity R and speci?c detectivity D* intimately with material properties and operating conditions. A compact Verilog-A based SPICE model is developed which can be directly combined with advanced digital Read-Out Integrated Circuit cell designs to simulate and optimize high performance Focal Plane Arrays which form a critical component in the rapidly expanding market of self-driven automotive, internet of things security, and embedded applications.
关键词： polycrystalline materials,PbSe photodetectors,carrier-type inversion,multiscale modeling,quantum efficiency,band structure,SPICE model
更新于2025-09-19 17:13:59
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Oxychalcogenide Perovskite Solar Cells: A Multiscale Design Approach
摘要： Herein, a multiscale approach is used to design solar cells with oxychalcogenide perovskite absorbers by combining atomistic calculations and macroscale device simulations and optimization. The method involves the computation of charge carrier recombination time as well as the carriers’ scattering time where lattice dynamics and multiple carrier scattering mechanisms are taken into account. Based on microscopically calculated parameters for the oxychalcogenide perovskites, a multiproperty optimization is performed to maximize the power conversion efficiency of the full device. This approach allows identifying optimal designs of some potential oxychalcogenide perovskite solar cells comprehensively. Herein, the methodology opens opportunities to accelerate lab realization and fabrication of solar cells with oxychalcogenide perovskite absorbers. Furthermore, the presented approach combines several general methods, and it should be highly beneficial in saving time and cost of device fabrication and optimization.
关键词： density functional theory,multiscale modeling,photovoltaics,oxychalcogenide perovskites,charge transport
更新于2025-09-19 17:13:59
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Electronic–Electromagnetic Multiphysics Modeling for Terahertz Plasmonics: A Review
摘要： In this article, we review numerical and analytical methods of electronic–electromagnetic multiphysics modeling for terahertz plasmonic applications. Approaches within semiclassical regime of electronic transport are considered, as these are appropriate for examining plasma-wave phenomenology in 2-D electron gas systems, commonly found in high-electron-mobility transistors (HEMTs) and graphene sheets. In modeling of such electronic–plasmonic devices, coupling of incident electromagnetic wave to the device or emission from the device needs to be modeled. Therefore, electronic–electromagnetic coupled multiphysics multiscale models are required. In such modeling problems, the domain consists of large regions where electrodynamic equations are to be solved. Therefore, overall time efficiency relies on the speed of solution of electrodynamic equations. Nevertheless, the electrodynamic solution’s speed is limited by the smallest grid sizes, which are a function of electronic transport equations. To address these issues, unconditionally stable finite-difference time-domain (FDTD) and iterative alternating directional implicit (ADI)-FDTD methods, coupled with hydrodynamic equations, are reviewed. Advantages and compromises between FDTD, ADI-FDTD, and iterative ADI-FDTD-based global modeling are discussed and conclusions are summarized.
关键词： electronic,numerical modeling,electron transport,terahertz (THz),FDTD,multiphysics,plasmonic,Alternating directional implicit finite-difference time-domain (ADI-FDTD),multiscale modeling,hydrodynamic (HD),plasma wave,electromagnetic
更新于2025-09-16 10:30:52
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The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling
摘要： The light-harvesting in photosynthetic purple bacteria can be tuned in response to the light conditions during cell growth. One of the used strategies is to change the energy of the excitons in the major light-harvesting complex, commonly known as LH2. In the present study we report the first systematic investigation of the microscopic origin of the exciton tuning using three complexes, namely the common (high-light) and the low-light forms of LH2 from Rps. acidophila plus a third complex analogous to the PucD complex from Rps. palustris. The study is based on the combination of classical molecular dynamics of each complex in a lipid membrane and excitonic calculations based on a multiscale quantum mechanics/molecular mechanics approach including a polarizable embedding. From the comparative analysis, it comes out that the mechanisms that govern the adaptation of the light conditions use the different H-bonding environment around the bacteriochlorophyll pigments to dynamically control both internal and inter-pigment degrees of freedom. While the former have a large effect on the site energies, the latter significantly change the electronic couplings, but only the combination of the two effects can fully reproduce the tuning of the final excitons and explain the observed spectroscopic differences.
关键词： purple bacteria,H-bonding environment,multiscale modeling,light-harvesting complexes,excitonic tuning
更新于2025-09-16 10:30:52
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Electron Transport in Nanoporous Graphene: Probing the Talbot Effect
摘要： Electrons in graphene can show diffraction and interference phenomena fully analogous to light thanks to their Dirac-like energy dispersion. However, it is not clear how this optical analogy persists in nanostructured graphene, for example, with pores. Nanoporous graphene (NPG) consisting of linked graphene nanoribbons has recently been fabricated using molecular precursors and bottom-up assembly (Moreno et al. Science 2018, 360, 199). We predict that electrons propagating in NPG exhibit the interference Talbot effect, analogous to photons in coupled waveguides. Our results are obtained by parameter-free atomistic calculations of real-sized NPG samples based on seamlessly integrated density functional theory and tight-binding regions. We link the origins of this interference phenomenon to the band structure of the NPG. Most importantly, we demonstrate how the Talbot effect may be detected experimentally using dual-probe scanning tunneling microscopy. Talbot interference of electron waves in NPG or other related materials may open up new opportunities for future quantum electronics, computing, or sensing.
关键词： multiscale modeling,electron transport,Nanoporous graphene,scanning probe microscopy,Talbot interference
更新于2025-09-04 15:30:14