Pub Date : 2024-07-18DOI: 10.1088/1361-651x/ad64f4
Wyatt A. Witzen, James D. Lamb, Mariyappan Arul Kumar, M. Echlin, T.M. Pollock, Irene Beyerlein
Geometrically necessary dislocation (GND) content is measured from mm3-scaled Ti7Al three-dimensional (3D) microstructural data using a theory extended for hexagonal close packed crystals, which accounts for basal, prismatic and pyramidal ⟨ c + a ⟩ type dislocation content. The Ti7Al samples have been mechanically pre-strained to two different strain levels, and will then be strained along the same axis in uniaxial tension during simulation. Both inter- and intragranular GNDs across the microstructures have been characterized, with a large contribution of pyramidal ⟨ c + a ⟩ GNDs, consistent with the relative slip activity involved in pre-straining. The spatially resolved crystallographic GND distributions within the 3D microstructures are used to instantiate a microstructure model for forward modeling deformation simulations by a dislocation density hardening elasto-viscoplastic fast Fourier transform (DD-EVPFFT) framework. Coarsening the voxel resolution during the initial microstructure construction procedure is shown to strongly impact both the magnitude and spatial distribution of the GNDs and in turn the forward deformation response of the pre-strained material. This study indicates that the voxel resolution desired when transferring from measured to model microstructures need not only be proportionally scaled with the microstructure but also sufficiently fine to capture the subgranular orientation gradients that may already be present in the material.
几何必备位错（GND）含量是通过按 mm3 缩放的 Ti7Al 三维（3D）微结构数据测量得出的，使用的是针对六方紧密堆积晶体扩展的理论，该理论考虑了基底、棱柱和金字塔⟨ c + a ⟩型位错含量。Ti7Al 样品经过机械预应变，达到两种不同的应变水平，然后在模拟过程中沿同一轴线进行单轴拉伸。整个微结构的晶间和晶内 GND 均已表征，其中金字塔形⟨ c + a ⟩ GND 的贡献较大，这与预应变中涉及的相对滑移活动相一致。三维微结构中空间分辨的晶体学 GND 分布被用于实例化微结构模型，通过位错密度硬化弹塑性-粘弹性快速傅立叶变换（DD-EVPFFT）框架进行前向建模变形模拟。研究表明，在初始微结构构建过程中粗化体素分辨率会对 GND 的大小和空间分布产生强烈影响，进而影响预应变材料的正向变形响应。这项研究表明，从测量结果到模型微观结构的转换过程中所需的体素分辨率不仅需要与微观结构成比例，还需要足够精细，以捕捉材料中可能已经存在的晶下取向梯度。
{"title":"Resolving crystallographic geometrically necessary dislocations in three dimensions in a hexagonal close packed titanium alloy","authors":"Wyatt A. Witzen, James D. Lamb, Mariyappan Arul Kumar, M. Echlin, T.M. Pollock, Irene Beyerlein","doi":"10.1088/1361-651x/ad64f4","DOIUrl":"https://doi.org/10.1088/1361-651x/ad64f4","url":null,"abstract":"\u0000 Geometrically necessary dislocation (GND) content is measured from mm3-scaled Ti7Al three-dimensional (3D) microstructural data using a theory extended for hexagonal close packed crystals, which accounts for basal, prismatic and pyramidal ⟨ c + a ⟩ type dislocation content. The Ti7Al samples have been mechanically pre-strained to two different strain levels, and will then be strained along the same axis in uniaxial tension during simulation. Both inter- and intragranular GNDs across the microstructures have been characterized, with a large contribution of pyramidal ⟨ c + a ⟩ GNDs, consistent with the relative slip activity involved in pre-straining. The spatially resolved crystallographic GND distributions within the 3D microstructures are used to instantiate a microstructure model for forward modeling deformation simulations by a dislocation density hardening elasto-viscoplastic fast Fourier transform (DD-EVPFFT) framework. Coarsening the voxel resolution during the initial microstructure construction procedure is shown to strongly impact both the magnitude and spatial distribution of the GNDs and in turn the forward deformation response of the pre-strained material. This study indicates that the voxel resolution desired when transferring from measured to model microstructures need not only be proportionally scaled with the microstructure but also sufficiently fine to capture the subgranular orientation gradients that may already be present in the material.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141824101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-14DOI: 10.1088/1361-651x/ad5b7b
Haris Mehmood and Hisham Nasser
Molybdenum Oxide (MoOx) has been used as a hole-extraction film for photovoltaic (PV) applications; however, its interaction with Germanium (Ge)-based solar cells is less understood. For the first time, this paper aims to physically model the Ge solar cell that incorporates MoOx for hole transportation at the front side of the PV device facing the sunlight. However, the charge transportation process within the PV device is influenced by several design parameters that need optimization. A higher work function of MoOx increases the barrier height against minority carriers of electrons which is beneficial for extricating holes at the front interface of MoOx/Ge. A progressive reduction in the recombination of charge carriers has been observed by including a passivation layer of amorphous silicon (i-a-Si:H). Similarly, inserting a passivation and back surface field (BSF) stack of i-a-Si:H strengthens the electric field and likewise reduces the recombination at the rear side of the device. An enhanced doping concentration of BSF assists in the favorable alignment of energy bands for improved charge transportation within the solar cell as the rear passivation maintains the field strength for accelerated movement of charge carriers. However, optimizing the thickness of the front-passivation film is challenging due to the parasitic absorption of light at larger thicknesses. A comparative study with the reference device revealed that the proposed device exhibited a step-increase in the conversion efficiency (η) from 4.23% to 13.10%, with a higher Jsc of 46.4 mA cm−2, Voc of 383 mV, and FF of 74%. The proposed study is anticipated to meet the research gap in the physical device modelling of Ge-based solar cells employing high work function MoOx as a carrier-selective layer that could be conducive to the development of highly efficient multijunction solar cells.
氧化钼（MoOx）已被用作光伏（PV）应用中的空穴萃取薄膜；然而，人们对它与基于锗（Ge）的太阳能电池之间的相互作用了解较少。本文首次旨在建立 Ge 太阳能电池的物理模型，该模型在光伏设备面向阳光的前端加入了用于空穴传输的 MoOx。然而，光伏器件内的电荷传输过程受到多个设计参数的影响，需要进行优化。氧化钼的功函数越高，对电子少数载流子的阻挡高度就越高，这有利于在氧化钼/锗的前端界面挤出空穴。加入非晶硅（i-a-Si:H）钝化层后，电荷载流子的重组逐渐减少。同样，插入 i-a-Si:H的钝化和背表面场（BSF）堆栈可增强电场，并同样减少器件后侧的重组。提高 BSF 的掺杂浓度有助于能带的良好排列，从而改善太阳能电池内部的电荷传输，因为背面钝化可保持电场强度，加速电荷载流子的移动。然而，由于前钝化膜厚度较大时会产生寄生光吸收，因此优化前钝化膜的厚度具有挑战性。与参考器件的比较研究表明，拟议器件的转换效率 (η)从 4.23% 逐步提高到 13.10%，Jsc 为 46.4 mA cm-2，Voc 为 383 mV，FF 为 74%。预计该研究将填补采用高功函数 MoOx 作为载流子选择层的 Ge 基太阳能电池物理器件建模方面的研究空白，有利于开发高效多结太阳能电池。
{"title":"TCAD simulation of germanium-based heterostructure solar cell employing molybdenum oxide as a hole-selective layer","authors":"Haris Mehmood and Hisham Nasser","doi":"10.1088/1361-651x/ad5b7b","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5b7b","url":null,"abstract":"Molybdenum Oxide (MoOx) has been used as a hole-extraction film for photovoltaic (PV) applications; however, its interaction with Germanium (Ge)-based solar cells is less understood. For the first time, this paper aims to physically model the Ge solar cell that incorporates MoOx for hole transportation at the front side of the PV device facing the sunlight. However, the charge transportation process within the PV device is influenced by several design parameters that need optimization. A higher work function of MoOx increases the barrier height against minority carriers of electrons which is beneficial for extricating holes at the front interface of MoOx/Ge. A progressive reduction in the recombination of charge carriers has been observed by including a passivation layer of amorphous silicon (i-a-Si:H). Similarly, inserting a passivation and back surface field (BSF) stack of i-a-Si:H strengthens the electric field and likewise reduces the recombination at the rear side of the device. An enhanced doping concentration of BSF assists in the favorable alignment of energy bands for improved charge transportation within the solar cell as the rear passivation maintains the field strength for accelerated movement of charge carriers. However, optimizing the thickness of the front-passivation film is challenging due to the parasitic absorption of light at larger thicknesses. A comparative study with the reference device revealed that the proposed device exhibited a step-increase in the conversion efficiency (η) from 4.23% to 13.10%, with a higher Jsc of 46.4 mA cm−2, Voc of 383 mV, and FF of 74%. The proposed study is anticipated to meet the research gap in the physical device modelling of Ge-based solar cells employing high work function MoOx as a carrier-selective layer that could be conducive to the development of highly efficient multijunction solar cells.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141717739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-12DOI: 10.1088/1361-651x/ad627e
W. Verdier, A. Cartalade, M. Plapp
A methodology is built to model and simulate the dynamics of domain coarsening of a two-phase ternary liquid with an arbitrary phase diagram. High numerical performance is obtained through the use of the phase field-method for interface capturing, a lattice Boltzmann method numerical scheme for all the model equations, and a portable, parallel simulation code running on multiple GPUs. The model is benchmarked against an analytic solution for a ternary diffusion couple. It also reproduces the well-known power law for droplet coarsening during Ostwald ripening without fluid flow. Large-scale simulations with flow illustrate the effects of momentum transport and buoyancy, as well as droplet coalescence and sedimentation.
{"title":"Grand-potential phase field simulations of droplet growth and sedimentation in a two-phase ternary fluid","authors":"W. Verdier, A. Cartalade, M. Plapp","doi":"10.1088/1361-651x/ad627e","DOIUrl":"https://doi.org/10.1088/1361-651x/ad627e","url":null,"abstract":"\u0000 A methodology is built to model and simulate the dynamics of domain coarsening of a two-phase ternary liquid with an arbitrary phase diagram. High numerical performance is obtained through the use of the phase field-method for interface capturing, a lattice Boltzmann method numerical scheme for all the model equations, and a portable, parallel simulation code running on multiple GPUs. The model is benchmarked against an analytic solution for a ternary diffusion couple. It also reproduces the well-known power law for droplet coarsening during Ostwald ripening without fluid flow. Large-scale simulations with flow illustrate the effects of momentum transport and buoyancy, as well as droplet coalescence and sedimentation.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141652160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study primarily concentrates on the layer optimization and structural refinement of carbon fiber composite B-pillars. In the initial phase, an initial layer configuration for the carbon fiber composite material B-pillar was devised, followed by comprehensive finite element numerical simulations. The weight of the B-pillar was effectively diminished by 44.9% compared to its metal counterpart, while maintaining consistent performance across diverse operational conditions. Subsequently, an advanced layer thickness optimization model was formulated, incorporating the innovative "super layer" concept. Integration of simulation software, such as ISIGHT and ABAQUS, facilitated the determination of optimal layer thickness and ratio for the composite material. The layer order was systematically optimized through the application of a discrete particle swarm optimization algorithm based on exchange order, adeptly addressing issues related to discontinuous design variables and potential combinations. The incorporation of a ply drop-off structure laying scheme was derived, resulting in an impressive weight reduction of 57.5%. In the final phase, adherence to NCAP side collision testing standards enabled a comprehensive evaluation, wherein various indicators including deformation mode, intrusion amount, and intrusion speed were employed. The results substantiate that the composite B-pillar exhibits equivalent side impact resistance to the original metal B-pillar, ensuring robust passenger protection.
本研究主要集中于碳纤维复合材料 B 柱的层优化和结构细化。在初始阶段，设计了碳纤维复合材料 B 柱的初始层配置，随后进行了全面的有限元数值模拟。与金属材料相比，B 柱的重量有效减轻了 44.9%，同时在各种运行条件下保持了稳定的性能。随后，结合创新的 "超级层 "概念，制定了先进的层厚度优化模型。ISIGHT 和 ABAQUS 等仿真软件的集成有助于确定复合材料的最佳层厚度和比率。通过应用基于交换顺序的离散粒子群优化算法，对层序进行了系统优化，巧妙地解决了与不连续设计变量和潜在组合相关的问题。通过采用层间距结构铺设方案，重量减轻了 57.5%，令人印象深刻。在最后阶段，按照 NCAP 侧面碰撞测试标准进行了全面评估，采用了包括变形模式、侵入量和侵入速度在内的各种指标。结果证明，复合材料 B 柱的侧面抗冲击性能与原来的金属 B 柱相当，确保了对乘客的有力保护。
{"title":"Mechanical performance simulation and optimal design of carbon fiber composite B-pillar","authors":"Jianhui Zhang, Yaopeng Hu, Qingchun Li, changcheng yin","doi":"10.1088/1361-651x/ad6202","DOIUrl":"https://doi.org/10.1088/1361-651x/ad6202","url":null,"abstract":"\u0000 This study primarily concentrates on the layer optimization and structural refinement of carbon fiber composite B-pillars. In the initial phase, an initial layer configuration for the carbon fiber composite material B-pillar was devised, followed by comprehensive finite element numerical simulations. The weight of the B-pillar was effectively diminished by 44.9% compared to its metal counterpart, while maintaining consistent performance across diverse operational conditions. Subsequently, an advanced layer thickness optimization model was formulated, incorporating the innovative \"super layer\" concept. Integration of simulation software, such as ISIGHT and ABAQUS, facilitated the determination of optimal layer thickness and ratio for the composite material. The layer order was systematically optimized through the application of a discrete particle swarm optimization algorithm based on exchange order, adeptly addressing issues related to discontinuous design variables and potential combinations. The incorporation of a ply drop-off structure laying scheme was derived, resulting in an impressive weight reduction of 57.5%. In the final phase, adherence to NCAP side collision testing standards enabled a comprehensive evaluation, wherein various indicators including deformation mode, intrusion amount, and intrusion speed were employed. The results substantiate that the composite B-pillar exhibits equivalent side impact resistance to the original metal B-pillar, ensuring robust passenger protection.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141656243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-10DOI: 10.1088/1361-651x/ad5dd4
Atsuo Hirano, Yosuke Tsunemoto and Akiyuki Takahashi
Classical molecular dynamics (MD) is extensively employed to explore the properties, deformations, and fractures of materials at the atomic scale. Identifying local structures is crucial for understanding the mechanisms behind material deformation and fracture. Nevertheless, analyzing the local lattice structure at high temperatures poses challenges due to atomic thermal fluctuations, which act as noise and potentially lead to misjudgment of the local lattice structure. To date, various strategies have been implemented to circumvent this issue. However, they cannot be a solution because it is unable to reproduce phenomena unique to high temperatures, whereas others require significant computational resources. This paper introduces an innovative method to reduce atomic thermal fluctuations using a straightforward algorithm, thereby facilitating accurate identification of local lattice structures even at high temperatures. Our approach incorporates novel degrees of freedom, termed ‘Markers,’ that are linked to atoms. By reducing the thermal fluctuation of these Markers, precise analysis of the local lattice structure becomes feasible. The efficacy of this method is validated through its thermal reducibility and Markers trackabilities to atoms. Utilizing common neighbor analysis, the error rate for structure identification with our method is nearly 0% at temperatures up to 1200 K in Fe, in contrast to approximately 5% without it. Furthermore, the average distance between atoms and Markers remains below 0.1 Å. Applying our method to phase transformations, we successfully observed the transition from face-centered cubic to body-centered cubic structure in Fe at 1200 K. This method holds promise for expanding the capabilities of MD simulations at high temperatures.
经典分子动力学（MD）被广泛用于探索材料在原子尺度上的特性、变形和断裂。识别局部结构对于理解材料变形和断裂背后的机理至关重要。然而，在高温条件下分析局部晶格结构是一项挑战，因为原子热波动是一种噪声，有可能导致对局部晶格结构的误判。迄今为止，人们已经实施了各种策略来规避这一问题。然而，这些方法都无法解决这一问题，因为它们无法再现高温下的特有现象，而其他方法则需要大量的计算资源。本文介绍了一种创新方法，利用一种简单的算法来减少原子热波动，从而即使在高温下也能准确识别局部晶格结构。我们的方法包含了与原子相连的新自由度，称为 "标记"。通过减少这些标记的热波动，就可以对局部晶格结构进行精确分析。这种方法的有效性通过其热还原性和标记与原子的可跟踪性得到了验证。利用共邻分析，在温度高达 1200 K 的铁元素中，使用我们的方法进行结构识别的错误率几乎为 0%，而不使用这种方法的错误率约为 5%。此外，原子与 Markers 之间的平均距离保持在 0.1 Å 以下。将我们的方法应用于相变，我们成功观测到铁在 1200 K 时从面心立方结构向体心立方结构的转变。
{"title":"Atomic thermal fluctuation reduction method for robust local lattice structure identification in finite-temperature molecular dynamics","authors":"Atsuo Hirano, Yosuke Tsunemoto and Akiyuki Takahashi","doi":"10.1088/1361-651x/ad5dd4","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5dd4","url":null,"abstract":"Classical molecular dynamics (MD) is extensively employed to explore the properties, deformations, and fractures of materials at the atomic scale. Identifying local structures is crucial for understanding the mechanisms behind material deformation and fracture. Nevertheless, analyzing the local lattice structure at high temperatures poses challenges due to atomic thermal fluctuations, which act as noise and potentially lead to misjudgment of the local lattice structure. To date, various strategies have been implemented to circumvent this issue. However, they cannot be a solution because it is unable to reproduce phenomena unique to high temperatures, whereas others require significant computational resources. This paper introduces an innovative method to reduce atomic thermal fluctuations using a straightforward algorithm, thereby facilitating accurate identification of local lattice structures even at high temperatures. Our approach incorporates novel degrees of freedom, termed ‘Markers,’ that are linked to atoms. By reducing the thermal fluctuation of these Markers, precise analysis of the local lattice structure becomes feasible. The efficacy of this method is validated through its thermal reducibility and Markers trackabilities to atoms. Utilizing common neighbor analysis, the error rate for structure identification with our method is nearly 0% at temperatures up to 1200 K in Fe, in contrast to approximately 5% without it. Furthermore, the average distance between atoms and Markers remains below 0.1 Å. Applying our method to phase transformations, we successfully observed the transition from face-centered cubic to body-centered cubic structure in Fe at 1200 K. This method holds promise for expanding the capabilities of MD simulations at high temperatures.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/1361-651x/ad60e7
R. AL-Hamadany, J. Goss, P. Briddon
Using density functional theory calculations, the interaction between oxygen vacancies and carbon in bi-axially strained SrTiO3 has been investigated. CTi-Vo binding energy and reorientation of CTi have been examined for ±1%, ±2%, ±3% and ±4% compressive and tensile strains. The results show that compressive strain is an effective route to restrict the diffusion of electrically active VO in the presence of CTidopants. According to our results the reorientation barrier volumetric and bi-axial strain dependences differ in the compression and tension regimes and is expected to affect dielectric characteristics of SrTiO3 under an alternating electric field.
{"title":"A Route for Tunable C-Vo Doped Perovskite SrTiO3Functionalities Through Epitaxial Strain Engineering","authors":"R. AL-Hamadany, J. Goss, P. Briddon","doi":"10.1088/1361-651x/ad60e7","DOIUrl":"https://doi.org/10.1088/1361-651x/ad60e7","url":null,"abstract":"\u0000 Using density functional theory calculations, the interaction between oxygen vacancies and carbon in bi-axially strained SrTiO3 has been investigated. CTi-Vo binding energy and reorientation of CTi have been examined for ±1%, ±2%, ±3% and ±4% compressive and tensile strains. The results show that compressive strain is an effective route to restrict the diffusion of electrically active VO in the presence of CTidopants. According to our results the reorientation barrier volumetric and bi-axial strain dependences differ in the compression and tension regimes and is expected to affect dielectric characteristics of SrTiO3 under an alternating electric field.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141664616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-09DOI: 10.1088/1361-651x/ad60e8
J. Bonneville, Christophe Coupeau, J. Douin, R. Gröger
We recently developed an experimental device that allows us to observe the slip traces under stress at the atomic scale. Here, we report experimental results obtained at the latter scale on Nb single crystals making it possible to observe dislocation dipoles, which are evidenced by two slip traces formed by emerging moving dislocations of opposite Burgers vectors ending very close to each other. The geometry and stability of the dislocation dipoles were fully characterized in the framework of linear anisotropic elasticity theory and by atomistic simulations. This allows us to calculate a local opposite stress impeding dislocation motion of the dislocations of the dipole.
{"title":"Screw dislocation dipoles in niobium: combination of STM observations and atomistic simulations","authors":"J. Bonneville, Christophe Coupeau, J. Douin, R. Gröger","doi":"10.1088/1361-651x/ad60e8","DOIUrl":"https://doi.org/10.1088/1361-651x/ad60e8","url":null,"abstract":"\u0000 We recently developed an experimental device that allows us to observe the slip traces under stress at the atomic scale. Here, we report experimental results obtained at the latter scale on Nb single crystals making it possible to observe dislocation dipoles, which are evidenced by two slip traces formed by emerging moving dislocations of opposite Burgers vectors ending very close to each other. The geometry and stability of the dislocation dipoles were fully characterized in the framework of linear anisotropic elasticity theory and by atomistic simulations. This allows us to calculate a local opposite stress impeding dislocation motion of the dislocations of the dipole.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141663777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-651x/ad5f4a
R. Dingreville, Andreas E Robertson, Vahid Attari, Michael Greenwood, N. Ofori-Opoku, Mythreyi Ramesh, Peter W. Voorhees, Qian Zhang
We present a comprehensive benchmarking framework for evaluating machine-learning approaches applied to phase-field problems. This framework focuses on four key analysis areas crucial for assessing the performance of such approaches in a systematic and structured way. Firstly, interpolation tasks are examined to identify trends in prediction accuracy and accumulation of error over simulation time. Secondly, extrapolation tasks are also evaluated according to the same metrics. Thirdly, the relationship between model performance and data requirements is investigated to understand the impact on predictions and robustness of these approaches. Finally, systematic errors are analyzed to identify specific events or inadvertent rare events triggering high errors. Quantitative metrics evaluating the local and global description of the microstructure evolution, along with other scalar metrics representative of phase-field problems, are used across these four analysis areas. This benchmarking framework provides a path to evaluate the effectiveness and limitations of machine-learning strategies applied to phase-field problems, ultimately facilitating their practical application.
{"title":"Benchmarking machine learning strategies for phase-field problems","authors":"R. Dingreville, Andreas E Robertson, Vahid Attari, Michael Greenwood, N. Ofori-Opoku, Mythreyi Ramesh, Peter W. Voorhees, Qian Zhang","doi":"10.1088/1361-651x/ad5f4a","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5f4a","url":null,"abstract":"\u0000 We present a comprehensive benchmarking framework for evaluating machine-learning approaches applied to phase-field problems. This framework focuses on four key analysis areas crucial for assessing the performance of such approaches in a systematic and structured way. Firstly, interpolation tasks are examined to identify trends in prediction accuracy and accumulation of error over simulation time. Secondly, extrapolation tasks are also evaluated according to the same metrics. Thirdly, the relationship between model performance and data requirements is investigated to understand the impact on predictions and robustness of these approaches. Finally, systematic errors are analyzed to identify specific events or inadvertent rare events triggering high errors. Quantitative metrics evaluating the local and global description of the microstructure evolution, along with other scalar metrics representative of phase-field problems, are used across these four analysis areas. This benchmarking framework provides a path to evaluate the effectiveness and limitations of machine-learning strategies applied to phase-field problems, ultimately facilitating their practical application.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141680436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-651x/ad5f49
A. S. Mitra, Abraham Anapolsky, Edwin Garcia
A physics-based analytical methodology is presented to describe the debonding of a statistically representative electrochemically active particle from the surrounding binder-electrolyte matrix in a porous electrode. The proposed framework enables to determine the space of C-Rates and electrode particle radii that suppresses or enhances debonding and is graphically summarized into maps where four debonding mechanisms were identified: a) the spontaneous debonding mechanism, which occurs when the electrode particle spontaneously detaches from the matrix; b) the continuous debonding mechanism, which occurs when the electrode particle gradually loses contact with the surrounding matrix; c) the electrochemical cycling fatigue mechanism, which causes gradual growth of the flaw due to electrochemical cycling; and d) the microstructural debonding mechanism, which is a result of the microstructural stochastics of the electrode and is embodied in terms of the debonding probability of particles. The critical C-Rates for debonding demonstrate a mechanism-dependent power-law relation with respect to the particle radius, which enables the experimental identification of the failure mechanism thereby providing a context to formulate design strategies to minimize debonding and provide robust, physics-based, phenomenological, and statistics-based estimates for electrochemically driven failure.
本文提出了一种基于物理学的分析方法，用于描述多孔电极中具有统计代表性的电化学活性粒子与周围粘结剂-电解质基质的脱粘现象。所提出的框架能够确定抑制或增强脱落的 C 速率和电极颗粒半径空间，并以图形方式总结成地图，其中确定了四种脱落机制：a) 自发脱粘机制，即电极颗粒自发脱离基体；b) 连续脱粘机制，即电极颗粒逐渐失去与周围基体的接触；c) 电化学循环疲劳机制，即电化学循环导致缺陷逐渐增大；d) 微结构脱粘机制，即电极微结构随机性的结果，体现为颗粒的脱粘概率。脱粘的临界 C-Rates（C-速率）显示了与颗粒半径相关的幂律关系，这使得失效机制的实验鉴定成为可能，从而为制定设计策略提供了背景，以最大限度地减少脱粘，并为电化学驱动的失效提供可靠的、基于物理学、现象学和统计学的估计。
{"title":"Analytical Design of Electrode Particle Debonding for Battery Applications","authors":"A. S. Mitra, Abraham Anapolsky, Edwin Garcia","doi":"10.1088/1361-651x/ad5f49","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5f49","url":null,"abstract":"\u0000 A physics-based analytical methodology is presented to describe the debonding of a statistically representative electrochemically active particle from the surrounding binder-electrolyte matrix in a porous electrode. The proposed framework enables to determine the space of C-Rates and electrode particle radii that suppresses or enhances debonding and is graphically summarized into maps where four debonding mechanisms were identified: a) the spontaneous debonding mechanism, which occurs when the electrode particle spontaneously detaches from the matrix; b) the continuous debonding mechanism, which occurs when the electrode particle gradually loses contact with the surrounding matrix; c) the electrochemical cycling fatigue mechanism, which causes gradual growth of the flaw due to electrochemical cycling; and d) the microstructural debonding mechanism, which is a result of the microstructural stochastics of the electrode and is embodied in terms of the debonding probability of particles. The critical C-Rates for debonding demonstrate a mechanism-dependent power-law relation with respect to the particle radius, which enables the experimental identification of the failure mechanism thereby providing a context to formulate design strategies to minimize debonding and provide robust, physics-based, phenomenological, and statistics-based estimates for electrochemically driven failure.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141679878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1361-651x/ad5dd2
Mikael Santonen, A. Lahti, Z. Rad, M. Miettinen, Masoud ebrahimzadeh, J. Lehtiö, P. Laukkanen, M. Punkkinen, P. Paturi, K. Kokko, Antti Kuronen, Wei Li, L. Vitos, Katja Parkkinen, Markus Eklund
Polycrystalline silicon (poly-Si) significantly expands the properties of the ICT miracle material, silicon (Si). Depending on the grain size and shape as well as the grain boundary structure, the properties of poly-Si exceed what single crystal (c-Si) and amorphous (a-Si) silicon can offer, especially for radio frequency (RF) applications in microelectronics. Due to its wide range of applications and, on the one hand, its theoretically and technologically challenging microstructure, poly-Si research is the most timely. In this report, we describe how we simulate and analyse the phenomena and mechanisms that control the effect of poly-Si deposition parameters on the structure of the deposited poly-Si films using classical molecular dynamics simulations. The grain shape and size, degree of crystallinity, grain boundary structure and the stress of poly-Si films are determined depending on the growth temperature, temperature distribution in the growing film, deposition flux, flux variation and the energy transferred to the film surface due to the deposition flux. The main results include: (i) the dependence of the crystallinity profile of the deposited poly-Si films on the stress, temperature and the different parameters of the deposition flux, (ii) growth modes at the early stages of the deposition, (iii) interaction and stability of seed crystallites at the early stage of the deposition of poly-Si films and the transition from the isolated crystallite growth to the poly-Si growth, (iv) interplay of the temperature, crystallinity, crystal shape and heath conductivity of different Si phases, (v) four different stages of crystallite growth are described: nucleation, growth, disappearance and retardation.
{"title":"Polycrystalline silicon, a molecular dynamics study: Part I --- Deposition and growth modes","authors":"Mikael Santonen, A. Lahti, Z. Rad, M. Miettinen, Masoud ebrahimzadeh, J. Lehtiö, P. Laukkanen, M. Punkkinen, P. Paturi, K. Kokko, Antti Kuronen, Wei Li, L. Vitos, Katja Parkkinen, Markus Eklund","doi":"10.1088/1361-651x/ad5dd2","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5dd2","url":null,"abstract":"\u0000 Polycrystalline silicon (poly-Si) significantly expands the properties of the ICT miracle material, silicon (Si). Depending on the grain size and shape as well as the grain boundary structure, the properties of poly-Si exceed what single crystal (c-Si) and amorphous (a-Si) silicon can offer, especially for radio frequency (RF) applications in microelectronics. Due to its wide range of applications and, on the one hand, its theoretically and technologically challenging microstructure, poly-Si research is the most timely. In this report, we describe how we simulate and analyse the phenomena and mechanisms that control the effect of poly-Si deposition parameters on the structure of the deposited poly-Si films using classical molecular dynamics simulations. The grain shape and size, degree of crystallinity, grain boundary structure and the stress of poly-Si films are determined depending on the growth temperature, temperature distribution in the growing film, deposition flux, flux variation and the energy transferred to the film surface due to the deposition flux. The main results include: (i) the dependence of the crystallinity profile of the deposited poly-Si films on the stress, temperature and the different parameters of the deposition flux, (ii) growth modes at the early stages of the deposition, (iii) interaction and stability of seed crystallites at the early stage of the deposition of poly-Si films and the transition from the isolated crystallite growth to the poly-Si growth, (iv) interplay of the temperature, crystallinity, crystal shape and heath conductivity of different Si phases, (v) four different stages of crystallite growth are described: nucleation, growth, disappearance and retardation.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141687848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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