Pub Date : 2023-11-13DOI: 10.1088/1361-651x/ad084c
Monika Vsianska, Martin Friák, Mojmir Sob
Abstract Quantum-mechanical calculations have become an indispensable tool for computational materials science due to their unprecedented versatility and reliability. Focusing specifically on the Density Functional Theory (DFT), the reliability of its numerous implementations was tested and verified mostly for pure elements. An extensive testing of binaries, ternaries and more-component phases is still rather rare due to a vast configurational space that is nearly infinite already for binaries. Importantly, there are well known cases of theoretical predictions contradicting experiments. In this paper, we analyze the failure of theory to reproduce correctly the ground state of the Fe 3 Al intermetallic compound. Namely, most exchange-correlation (xc) energies within the generalized gradient approximation (GGA) predict this material in the L1 2 structure instead of the experimentally found D0 3 structure. We test the performance of 36 combinations of 6 different GGA parametrizations and 6 different Fe and Al potentials. These combinations are evaluated employing a multi-dimensional multi-criteria descriptor { ΔE , a , { μFe }, { C ij }} consisting of fundamental thermodynamic properties (energy difference ΔE between the D0 3 and L1 2 structures), a structural aspect (lattice parameter a ), electronic-structure related magnetic properties (local magnetic moments of Fe atoms { μFe }) and elastic properties (a complete set of second-order elastic constants { C ij }). Considering the thermodynamic stability as the most critical aspect, we identify the Perdew–Wang (1991) GGA xc-functional parametrization as the optimum for describing the electronic structure of the Fe 3 Al compound.
摘要量子力学计算以其前所未有的通用性和可靠性，已成为计算材料科学不可缺少的工具。特别关注密度泛函理论(DFT)，其众多实现的可靠性主要是针对纯元素进行了测试和验证。对二进制、三元和多组件阶段的广泛测试仍然相当罕见，因为对于二进制来说，巨大的配置空间几乎已经是无限的。重要的是，有一些众所周知的理论预测与实验相矛盾的案例。本文分析了理论不能正确再现铁铝金属间化合物基态的缺陷。也就是说，在广义梯度近似(GGA)中，大多数交换相关(xc)能量预测该材料为L1 2结构，而不是实验发现的D0 3结构。我们测试了6种不同的GGA参数和6种不同的Fe和Al电位的36种组合的性能。这些组合评估采用多维多标准描述符{ΔE, a,{μF E }, { C ij}}组成的基本热力学性质(能量差ΔE L1 D0 3和2之间的结构),结构方面(晶格参数),电子结构相关的磁性(本地铁原子的磁矩{μF E})和弹性属性(一套完整的二阶弹性常数C ij{})。考虑到热力学稳定性是最关键的方面，我们确定Perdew-Wang (1991) GGA xc功能参数化是描述fe3al化合物电子结构的最佳方法。
{"title":"A critical comparative review of generalized gradient approximation: the ground state of Fe3Al as a test case","authors":"Monika Vsianska, Martin Friák, Mojmir Sob","doi":"10.1088/1361-651x/ad084c","DOIUrl":"https://doi.org/10.1088/1361-651x/ad084c","url":null,"abstract":"Abstract Quantum-mechanical calculations have become an indispensable tool for computational materials science due to their unprecedented versatility and reliability. Focusing specifically on the Density Functional Theory (DFT), the reliability of its numerous implementations was tested and verified mostly for pure elements. An extensive testing of binaries, ternaries and more-component phases is still rather rare due to a vast configurational space that is nearly infinite already for binaries. Importantly, there are well known cases of theoretical predictions contradicting experiments. In this paper, we analyze the failure of theory to reproduce correctly the ground state of the Fe 3 Al intermetallic compound. Namely, most exchange-correlation (xc) energies within the generalized gradient approximation (GGA) predict this material in the L1 2 structure instead of the experimentally found D0 3 structure. We test the performance of 36 combinations of 6 different GGA parametrizations and 6 different Fe and Al potentials. These combinations are evaluated employing a multi-dimensional multi-criteria descriptor { <?CDATA $Delta E$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi mathvariant=\"normal\">Δ</mml:mi> <mml:mi>E</mml:mi> </mml:math> , a , { <?CDATA $mu^{mathrm{Fe}}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msup> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">F</mml:mi> <mml:mi mathvariant=\"normal\">e</mml:mi> </mml:mrow> </mml:mrow> </mml:msup> </mml:math> }, { C ij }} consisting of fundamental thermodynamic properties (energy difference <?CDATA $Delta E$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi mathvariant=\"normal\">Δ</mml:mi> <mml:mi>E</mml:mi> </mml:math> between the D0 3 and L1 2 structures), a structural aspect (lattice parameter a ), electronic-structure related magnetic properties (local magnetic moments of Fe atoms { <?CDATA $mu^{mathrm{Fe}}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msup> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">F</mml:mi> <mml:mi mathvariant=\"normal\">e</mml:mi> </mml:mrow> </mml:mrow> </mml:msup> </mml:math> }) and elastic properties (a complete set of second-order elastic constants { C ij }). Considering the thermodynamic stability as the most critical aspect, we identify the Perdew–Wang (1991) GGA xc-functional parametrization as the optimum for describing the electronic structure of the Fe 3 Al compound.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"59 21","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134993325","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 : 2023-11-10DOI: 10.1088/1361-651x/ad0b8b
Mikhail Khenner
Abstract Using a recent continuum model of a single-crystal nanowire morphological evolution in the applied axial electric field, an axisymmetric evolution of a microscopically rough nanowire surface is computed. Morphological evolution results in a wire breakup into a cylindrical segments (particles). Breakup time and the number of particles are characterized for various levels of the radial and axial surface roughness. It is shown that electromigration and larger surface roughness lead to a shorter breakup time and the increased number of particles.
{"title":"Nanowire Breakup via a Morphological Instability Enhanced by Surface Electromigration","authors":"Mikhail Khenner","doi":"10.1088/1361-651x/ad0b8b","DOIUrl":"https://doi.org/10.1088/1361-651x/ad0b8b","url":null,"abstract":"Abstract Using a recent continuum model of a single-crystal nanowire morphological evolution in the applied axial electric field, an axisymmetric evolution of a microscopically rough nanowire surface is computed. Morphological evolution results in a wire breakup into a cylindrical segments (particles). Breakup time and the number of particles are characterized for various levels of the radial and axial surface roughness. It is shown that electromigration and larger surface roughness lead to a shorter breakup time and the increased number of particles.&#xD;","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"86 21","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135092579","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 : 2023-11-10DOI: 10.1088/1361-651x/ad084d
Xiang Chen, Lei Liu, Rongjian Gao, Sheng Lu, Tao Fu
Abstract There have been numerous experimental studies conducted on the CoCrFeMnNi high entropy alloys (HEAs) at the macroscopic level. However, it is challenging to quantitatively analyze the shock behavior of the HEAs from a microscopic level through experiments. In this study, we construct single-crystal, twin-crystal, multilayer, hole, and two-phase structures of the CoCrFeMnNi HEAs using the molecular dynamics method. The effects of impact loading on the microscopic level are investigated for CoCrFeMnNi HEAs with different structures. By analyzing the evolution of their microstructure and the changes in physical parameters, the response laws and propagation characteristics of shock waves in various heterogeneous of CoCrFeMnNi HEAs are revealed at the atomic scale.
{"title":"Molecular dynamics simulation of the heterostructure of the CoCrFeMnNi high entropy alloy under an impact load","authors":"Xiang Chen, Lei Liu, Rongjian Gao, Sheng Lu, Tao Fu","doi":"10.1088/1361-651x/ad084d","DOIUrl":"https://doi.org/10.1088/1361-651x/ad084d","url":null,"abstract":"Abstract There have been numerous experimental studies conducted on the CoCrFeMnNi high entropy alloys (HEAs) at the macroscopic level. However, it is challenging to quantitatively analyze the shock behavior of the HEAs from a microscopic level through experiments. In this study, we construct single-crystal, twin-crystal, multilayer, hole, and two-phase structures of the CoCrFeMnNi HEAs using the molecular dynamics method. The effects of impact loading on the microscopic level are investigated for CoCrFeMnNi HEAs with different structures. By analyzing the evolution of their microstructure and the changes in physical parameters, the response laws and propagation characteristics of shock waves in various heterogeneous of CoCrFeMnNi HEAs are revealed at the atomic scale.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"68 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135087737","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 : 2023-11-10DOI: 10.1088/1361-651x/ad02b0
Baptiste Joste, Benoit Devincre, Riccardo Gatti, Henry Proudhon
Abstract Strain localization mechanisms taking place in polycrystal grains are investigated using Discrete Dislocation Dynamics (DDDs) simulations. First, elastic Finite Element Method simulations are used to calculate the intragranular stress distribution linked to strain incompatibilities between grains. Many configurations are tested to evaluate the stress heterogeneity and constitute a database for DDD simulations. From the analysis of these microstructures, a criterion is proposed to identify the grains where the emergence of the localization of the deformation is the most likely. Then, DDD simulations are used to explore the plastic strain localization phenomenon at the grain scale. Those simulations show that stress concentrations close to a polycrystal quadruple node can play a fundamental role in plastic strain localization. This work paves the way for future investigations to be made thanks to DDD simulations regarding slip band initiation and strain relaxation phenomena.
{"title":"Simulation of intragranular plastic deformation localization in FCC polycrystals by Discrete Dislocation Dynamics","authors":"Baptiste Joste, Benoit Devincre, Riccardo Gatti, Henry Proudhon","doi":"10.1088/1361-651x/ad02b0","DOIUrl":"https://doi.org/10.1088/1361-651x/ad02b0","url":null,"abstract":"Abstract Strain localization mechanisms taking place in polycrystal grains are investigated using Discrete Dislocation Dynamics (DDDs) simulations. First, elastic Finite Element Method simulations are used to calculate the intragranular stress distribution linked to strain incompatibilities between grains. Many configurations are tested to evaluate the stress heterogeneity and constitute a database for DDD simulations. From the analysis of these microstructures, a criterion is proposed to identify the grains where the emergence of the localization of the deformation is the most likely. Then, DDD simulations are used to explore the plastic strain localization phenomenon at the grain scale. Those simulations show that stress concentrations close to a polycrystal quadruple node can play a fundamental role in plastic strain localization. This work paves the way for future investigations to be made thanks to DDD simulations regarding slip band initiation and strain relaxation phenomena.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"74 17","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088357","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}
Abstract The effects of cutting crystal direction and speed on edge morphology, defects and electron transport characteristics were studied by molecular dynamics from the distribution state of defect atoms, the number of defect atoms, radial distribution function and anisotropy factor. The edge defects of zigzag graphene nanoribbons were extracted, and the difficulty of forming different kinds of defects and the influence of different defects on band gap were studied by density functional theory. The results indicate that cutting graphene along the [010] (zigzag) direction has a smaller anisotropy factor and smoother cutting. The obtained graphene nanoribbons have fewer defects and good edge quality. And the higher the cutting speed, the fewer defects and the smaller the anisotropy factor of the graphene nanoribbons formed, resulting in smaller damage. The typical defects at the edges include 5-8-5 defect (double-vacancy defect), 5-9SV defect (single-vacancy defect), SW (stone wales) defect, chain defect, crack defect and hole defect. Relationship between forming energy of different types of defects: crack defect > chain defect > SW defect > 5-9SV defect > 5-8-5 defect > hole defect. Hole defect is the most difficult to form. The band gap width of the cut edge containing defects is smaller than that of the perfect graphene nanoribbon, resulting in the increase of the conductivity of the graphene nanoribbon in the direction of metal characteristics. The presence of defects can open the band gap with of intrinsic graphene.
{"title":"Investigation on edge defect characteristics and electronic transport characteristics of graphene nano cutting","authors":"Meiling Tang, Zewei Yuan, Jingting Sun, Xiaohan Sun, Yan He, Xinbo Zhou","doi":"10.1088/1361-651x/ad0a41","DOIUrl":"https://doi.org/10.1088/1361-651x/ad0a41","url":null,"abstract":"Abstract The effects of cutting crystal direction and speed on edge morphology, defects and electron transport characteristics were studied by molecular dynamics from the distribution state of defect atoms, the number of defect atoms, radial distribution function and anisotropy factor. The edge defects of zigzag graphene nanoribbons were extracted, and the difficulty of forming different kinds of defects and the influence of different defects on band gap were studied by density functional theory. The results indicate that cutting graphene along the [010] (zigzag) direction has a smaller anisotropy factor and smoother cutting. The obtained graphene nanoribbons have fewer defects and good edge quality. And the higher the cutting speed, the fewer defects and the smaller the anisotropy factor of the graphene nanoribbons formed, resulting in smaller damage. The typical defects at the edges include 5-8-5 defect (double-vacancy defect), 5-9SV defect (single-vacancy defect), SW (stone wales) defect, chain defect, crack defect and hole defect. Relationship between forming energy of different types of defects: crack defect > chain defect > SW defect > 5-9SV defect > 5-8-5 defect > hole defect. Hole defect is the most difficult to form. The band gap width of the cut edge containing defects is smaller than that of the perfect graphene nanoribbon, resulting in the increase of the conductivity of the graphene nanoribbon in the direction of metal characteristics. The presence of defects can open the band gap with of intrinsic graphene.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135480017","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 : 2023-11-07DOI: 10.1088/1361-651x/ad0a42
Timmo Weidner, Vincent Taupin, Sylvie Demouchy, Karine Gouriet, Antoine Guitton, Patrick Cordier, Alexandre MUSSI
Abstract We propose a new procedure to extract information from electron tomography and use them as an input in a field dislocation mechanics. Dislocation electron tomography is an experimental technique that provides three-dimensional information on dislocation lines and Burgers vectors within a thin foil. The characterized 3D dislocation lines are used to construct the spatial distribution of the equivalent Nye dislocation density tensor. The model dislocation lattice incompatibility equation and stress balance equation are solved with a spectral code based on fast Fourier transform algorithms. As an output of the model, one obtains the three-dimensional distribution of mechanical fields, such as strains, rotations, stresses, resolved shear stresses and energy, inside the material. To assess the potential of the method, we consider two regions from a previously compressed olivine sample. Our results reveal significant local variations in local stress fields and resolved shear stresses in various slip systems, which can impact the strong plastic anisotropy of olivine and the activation of different dislocation slip systems. It also evidences the built-up of kinematic hardening down to the nanometre scale.
{"title":"From Electron Tomography of Dislocations to Field Dislocation Mechanics: Application to Olivine","authors":"Timmo Weidner, Vincent Taupin, Sylvie Demouchy, Karine Gouriet, Antoine Guitton, Patrick Cordier, Alexandre MUSSI","doi":"10.1088/1361-651x/ad0a42","DOIUrl":"https://doi.org/10.1088/1361-651x/ad0a42","url":null,"abstract":"Abstract We propose a new procedure to extract information from electron tomography and use them as an input in a field dislocation mechanics. Dislocation electron tomography is an experimental technique that provides three-dimensional information on dislocation lines and Burgers vectors within a thin foil. The characterized 3D dislocation lines are used to construct the spatial distribution of the equivalent Nye dislocation density tensor. The model dislocation lattice incompatibility equation and stress balance equation are solved with a spectral code based on fast Fourier transform algorithms. As an output of the model, one obtains the three-dimensional distribution of mechanical fields, such as strains, rotations, stresses, resolved shear stresses and energy, inside the material. To assess the potential of the method, we consider two regions from a previously compressed olivine sample. Our results reveal significant local variations in local stress fields and resolved shear stresses in various slip systems, which can impact the strong plastic anisotropy of olivine and the activation of different dislocation slip systems. It also evidences the built-up of kinematic hardening down to the nanometre scale.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"315 7","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135474923","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 : 2023-11-06DOI: 10.1088/1361-651x/ad09ea
MOHAMMAD A ALABDULLAH, Nasr M Ghoniem
Abstract We develop a computational method to determine the failure probability of brittle materials under general mechanical loading conditions. The method is a combination of two parts: (1) numerical simulations of materials with multiple cracks using phase field theory, where the complete fracture process is viewed as ”damage percolation” along critical paths or clusters of cracks, rather than the traditional weak-link failure mechanism of Weibull, and (2) an extension of the Batdorf statistical theory of fracture to finite domains, where it is implemented within the Finite Element (FE) framework. The results of phase-field simulations at the ”percolation threshold” are used as failure data in the Batdorf theory to determine the overall probability of failure. The input to this approach is the size distribution of cracks in a pristine material. An example is shown, where alumina samples that were previously tested by Abe and coworkers [1] in four-point loading are compared to the results of our numerical simulations. The approach developed here has the advantage of being extendable to more complex thermomechanical loading.
{"title":"A Probabilistic-Phase Field Model for the Fracture of Brittle Materials","authors":"MOHAMMAD A ALABDULLAH, Nasr M Ghoniem","doi":"10.1088/1361-651x/ad09ea","DOIUrl":"https://doi.org/10.1088/1361-651x/ad09ea","url":null,"abstract":"Abstract We develop a computational method to determine the failure probability of brittle materials under general mechanical loading conditions. The method is a combination of two parts: (1) numerical simulations of materials with multiple cracks using phase field theory, where the complete fracture process is viewed as ”damage percolation” along critical paths or clusters of cracks, rather than the traditional weak-link failure mechanism of Weibull, and (2) an extension of the Batdorf statistical theory of fracture to finite domains, where it is implemented within the Finite Element (FE) framework. The results of phase-field simulations at the ”percolation threshold” are used as failure data in the Batdorf theory to determine the overall probability of failure. The input to this approach is the size distribution of cracks in a pristine material. An example is shown, where alumina samples that were previously tested by Abe and coworkers [1] in four-point loading are compared to the results of our numerical simulations. The approach developed here has the advantage of being extendable to more complex thermomechanical loading.&#xD;","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"15 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135589250","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}
Abstract The fabrication of high-quality GaAs crystals is essential to approach optimal performance in optoelectronic and microelectronic devices. In this study, a molecular dynamics simulation study was conducted for the solidification of liquid GaAs at three cooling rates (10 10 K s −1 , 10 11 K s −1 , and 10 12 K s −1 ) at 300 K. The structural evolution in terms of crystal structure and defect formation in GaAs was thoroughly investigated using pair distribution function, average atomic energy, the largest standard cluster analysis, and visualization techniques. The results showed that the cooling rate of 10 10 K s −1 led to the development of the best crystal quality with ease of eutectic twin grain boundary coherent twin boundary formation. Increasing the cooling rates to 10 11 K s −1 and 10 12 K s −1 resulted in the amorphous structure. Both high and low cooling rates profoundly affected the formation of As 8 structure, but a maximum amount of 2.2% of As 8 crystal structure was formed at a cooling rate of 10 11 K s −1 . The reduction in cooling rate to 10 10 K s −1 induced the formation of numerous Schottky and Frenkel types of partial dislocations in the GaAs system. Results of this study can serve as potential guidelines to the theory of crystal growth and may be implemented in the fabrication of high-quality GaAs crystals for optimal device performance.
制备高质量的砷化镓晶体对于实现光电和微电子器件的最佳性能至关重要。在本研究中，对300 K下三种冷却速率(10 10 K s−1、10 11 K s−1和10 12 K s−1)下液态砷化镓的凝固进行了分子动力学模拟研究。利用对分布函数、平均原子能量、最大标准聚类分析和可视化技术深入研究了砷化镓晶体结构和缺陷形成方面的结构演变。结果表明，在10 ~ 10 K s−1的冷却速率下，晶体质量最好，易于形成共晶孪晶界。将冷却速率提高到10 11 K s−1和10 12 K s−1，形成非晶结构。高冷却速率和低冷却速率对As - 8结构的形成都有较大影响，但在冷却速率为10 11 K s−1时，As - 8晶体结构的形成量最大，为2.2%。当冷却速率降低到1010ks−1时，砷化镓体系中形成了许多Schottky和Frenkel类型的部分位错。本研究结果可作为晶体生长理论的潜在指导，并可用于制造高质量的GaAs晶体以获得最佳器件性能。
{"title":"Influence of cooling rate on microstructure and defect evolution in GaAs during solidification","authors":"Siyuan Wang, Qian Chen, Yongkai Yuan, Tinghong Gao, Yongchao Liang, Zean Tian, Anqi Yang","doi":"10.1088/1361-651x/ad041b","DOIUrl":"https://doi.org/10.1088/1361-651x/ad041b","url":null,"abstract":"Abstract The fabrication of high-quality GaAs crystals is essential to approach optimal performance in optoelectronic and microelectronic devices. In this study, a molecular dynamics simulation study was conducted for the solidification of liquid GaAs at three cooling rates (10 10 K s −1 , 10 11 K s −1 , and 10 12 K s −1 ) at 300 K. The structural evolution in terms of crystal structure and defect formation in GaAs was thoroughly investigated using pair distribution function, average atomic energy, the largest standard cluster analysis, and visualization techniques. The results showed that the cooling rate of 10 10 K s −1 led to the development of the best crystal quality with ease of eutectic twin grain boundary coherent twin boundary formation. Increasing the cooling rates to 10 11 K s −1 and 10 12 K s −1 resulted in the amorphous structure. Both high and low cooling rates profoundly affected the formation of As 8 structure, but a maximum amount of 2.2% of As 8 crystal structure was formed at a cooling rate of 10 11 K s −1 . The reduction in cooling rate to 10 10 K s −1 induced the formation of numerous Schottky and Frenkel types of partial dislocations in the GaAs system. Results of this study can serve as potential guidelines to the theory of crystal growth and may be implemented in the fabrication of high-quality GaAs crystals for optimal device performance.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135634634","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 : 2023-11-03DOI: 10.1088/1361-651x/ad0068
Zheng Qiu-Yang, Zhou Zhen-Yu, Li Yu, Chen Jianhao, Ye Sen-Bin, Piao Zhong-Yu
Abstract The research delves into the uncharted terrain of crystal orientation’s effect on high-frequency vibration-assisted processing of single-crystal copper, employing molecular dynamics to devise non-vibration, one-dimensional (1D), and two-dimensional (2D) vibration-assisted scratching models. The innovative discovery is the ‘peak-shaving’ effect, invoked by high-frequency vibration, which significantly mitigates surface irregularities on single-crystal copper, enhancing surface quality and material plasticity, thereby facilitating machinability. A key revelation is the superior efficacy of 2D vibration in material fortification relative to 1D vibration. Another novel finding is the amplified plasticity of single-crystal copper with a (111) crystal orientation under vibration-assisted excitation, linked to the varying directions of dislocation slip contingent upon crystal orientations. The pioneering observation that the induction of vibration during scratching dynamically propels dislocation defect structures, leading to the generation of a significant volume of vacant and interstitial atomic sites, underscores the pronounced influence of 2D vibration. This research contributes invaluable microscopic perspectives into the operative mechanism of crystal orientation’s impact on high-frequency vibration-assisted processing.
{"title":"Molecular dynamic simulation of the influence of vibration effects on scratching processes in Varied crystal orientations","authors":"Zheng Qiu-Yang, Zhou Zhen-Yu, Li Yu, Chen Jianhao, Ye Sen-Bin, Piao Zhong-Yu","doi":"10.1088/1361-651x/ad0068","DOIUrl":"https://doi.org/10.1088/1361-651x/ad0068","url":null,"abstract":"Abstract The research delves into the uncharted terrain of crystal orientation’s effect on high-frequency vibration-assisted processing of single-crystal copper, employing molecular dynamics to devise non-vibration, one-dimensional (1D), and two-dimensional (2D) vibration-assisted scratching models. The innovative discovery is the ‘peak-shaving’ effect, invoked by high-frequency vibration, which significantly mitigates surface irregularities on single-crystal copper, enhancing surface quality and material plasticity, thereby facilitating machinability. A key revelation is the superior efficacy of 2D vibration in material fortification relative to 1D vibration. Another novel finding is the amplified plasticity of single-crystal copper with a (111) crystal orientation under vibration-assisted excitation, linked to the varying directions of dislocation slip contingent upon crystal orientations. The pioneering observation that the induction of vibration during scratching dynamically propels dislocation defect structures, leading to the generation of a significant volume of vacant and interstitial atomic sites, underscores the pronounced influence of 2D vibration. This research contributes invaluable microscopic perspectives into the operative mechanism of crystal orientation’s impact on high-frequency vibration-assisted processing.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"5 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135868799","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 : 2023-11-03DOI: 10.1088/1361-651x/ad064f
Hoang-Giang Nguyen, Te-Hua Fang
Abstract The mechanical behavior of AlCuNiTi alloy during orthogonal micro-cutting consists of conventional cutting and complex-dimensional vibration cutting (CDVC) are investigated using molecular dynamics. The material removal mechanism is studied in terms of phase angle, amplitude ratio, and vibration frequency. In both techniques, the stress and strain are localized in the contiguous location between the sample and the cutting tool. The sample temperature during CDVC is noticeably greater than during classical cutting, which might benefit the transition phase and make CDVC smoother. The total mean value cutting force of the CDVC decreases as the frequencies of vibration and ratios of amplitude increase; however, the mean values of force under the CDVC with different phase angles demonstrate hardly ever statistically significant change. The quantity of atoms in the chip indicates that the machined surface rate is higher under the CDVC, with a higher frequency of vibration, smaller phase angle, and amplitude ratio. Under CDVC, the chip of plastic deformation gets more pronounced and severe with a frequency of oscillation at 150 GHz, an amplitude at 1.5, and a phase angle degree of 75° due to the lowest cutting ratio.
{"title":"Mechanics of AlCuNiTi alloy orthogonal micro-cutting","authors":"Hoang-Giang Nguyen, Te-Hua Fang","doi":"10.1088/1361-651x/ad064f","DOIUrl":"https://doi.org/10.1088/1361-651x/ad064f","url":null,"abstract":"Abstract The mechanical behavior of AlCuNiTi alloy during orthogonal micro-cutting consists of conventional cutting and complex-dimensional vibration cutting (CDVC) are investigated using molecular dynamics. The material removal mechanism is studied in terms of phase angle, amplitude ratio, and vibration frequency. In both techniques, the stress and strain are localized in the contiguous location between the sample and the cutting tool. The sample temperature during CDVC is noticeably greater than during classical cutting, which might benefit the transition phase and make CDVC smoother. The total mean value cutting force of the CDVC decreases as the frequencies of vibration and ratios of amplitude increase; however, the mean values of force under the CDVC with different phase angles demonstrate hardly ever statistically significant change. The quantity of atoms in the chip indicates that the machined surface rate is higher under the CDVC, with a higher frequency of vibration, smaller phase angle, and amplitude ratio. Under CDVC, the chip of plastic deformation gets more pronounced and severe with a frequency of oscillation at 150 GHz, an amplitude at 1.5, and a phase angle degree of 75° due to the lowest cutting ratio.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"166 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775753","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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