Pub Date : 2024-04-16DOI: 10.1088/1361-651x/ad39ff
Simon Gramatte, Vladyslav Turlo, Olivier Politano
In this study, we critically evaluate the performance of various interatomic potentials/force fields against a benchmark ab initio database for bulk amorphous alumina. The interatomic potentials tested in this work include all major fixed charge and variable charge models developed to date for alumina. Additionally, we introduce a novel machine learning interatomic potential constructed using the NequIP framework based on graph neural networks. Our findings reveal that the fixed-charge potential developed by Matsui and coworkers offers the most optimal balance between computational efficiency and agreement with ab initio data for stoichiometric alumina. Such balance cannot be provided by machine learning potentials when comparing performance with Matsui potential on the same computing infrastructure using a single Graphical Processing Unit. For non-stoichiometric alumina, the variable charge potentials, in particular ReaxFF, exhibit an impressive concordance with density functional theory calculations. However, our NequIP potentials trained on a small fraction of the ab initio database easily surpass ReaxFF in terms of both accuracy and computational performance. This is achieved without large overhead in terms of potential fitting and fine-tuning, often associated with the classical potential development process as well as training of standard deep neural network potentials, thus advocating for the use of data-efficient machine learning potentials like NequIP for complex cases of non-stoichiometric amorphous oxides.
在本研究中，我们根据针对块状无定形氧化铝的基准 ab initio 数据库，对各种原子间势/力场的性能进行了严格评估。这项工作中测试的原子间势包括迄今为止针对氧化铝开发的所有主要固定电荷和可变电荷模型。此外，我们还采用基于图神经网络的 NequIP 框架构建了一种新型机器学习原子间势。我们的研究结果表明，Matsui 及其同事开发的定电荷势在计算效率和与原子序数氧化铝的原子序数数据的一致性之间实现了最佳平衡。在使用单个图形处理单元的相同计算基础设施上比较机器学习势能与松井势能的性能时，机器学习势能无法提供这种平衡。对于非化学计量氧化铝，可变电荷势，尤其是 ReaxFF，与密度泛函理论计算的一致性令人印象深刻。然而，我们在一小部分原子序数数据库上训练的 NequIP 电位在准确性和计算性能方面都轻松超越了 ReaxFF。在实现这一目标的过程中，无需进行大量的电位拟合和微调（通常与经典的电位开发过程以及标准深度神经网络电位的训练有关），因此主张在非化学计量无定形氧化物的复杂情况下使用像 NequIP 这样数据高效的机器学习电位。
{"title":"Do we really need machine learning interatomic potentials for modeling amorphous metal oxides? Case study on amorphous alumina by recycling an existing ab initio database","authors":"Simon Gramatte, Vladyslav Turlo, Olivier Politano","doi":"10.1088/1361-651x/ad39ff","DOIUrl":"https://doi.org/10.1088/1361-651x/ad39ff","url":null,"abstract":"In this study, we critically evaluate the performance of various interatomic potentials/force fields against a benchmark <italic toggle=\"yes\">ab initio</italic> database for bulk amorphous alumina. The interatomic potentials tested in this work include all major fixed charge and variable charge models developed to date for alumina. Additionally, we introduce a novel machine learning interatomic potential constructed using the NequIP framework based on graph neural networks. Our findings reveal that the fixed-charge potential developed by Matsui and coworkers offers the most optimal balance between computational efficiency and agreement with <italic toggle=\"yes\">ab initio</italic> data for stoichiometric alumina. Such balance cannot be provided by machine learning potentials when comparing performance with Matsui potential on the same computing infrastructure using a single Graphical Processing Unit. For non-stoichiometric alumina, the variable charge potentials, in particular ReaxFF, exhibit an impressive concordance with density functional theory calculations. However, our NequIP potentials trained on a small fraction of the <italic toggle=\"yes\">ab initio</italic> database easily surpass ReaxFF in terms of both accuracy and computational performance. This is achieved without large overhead in terms of potential fitting and fine-tuning, often associated with the classical potential development process as well as training of standard deep neural network potentials, thus advocating for the use of data-efficient machine learning potentials like NequIP for complex cases of non-stoichiometric amorphous oxides.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140614117","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 : 2024-04-15DOI: 10.1088/1361-651x/ad3e99
A. Patra, C N Tomé
This work presents a dislocation density-based crystal plasticity constitutive model for glide kinetics, strengthening and dislocation density evolution, implemented in the effective medium-based Visco-Plastic Self Consistent (VPSC) framework and the spatially resolved, ρ-CP crystal plasticity finite element framework. Additionally, a distribution of intragranular stresses is introduced in the VPSC framework, instead of the conventionally used mean value of grain stress for effective medium calculations. The ρ-CP model is first calibrated to predict the mechanical response of a bcc ferritic steel with an initial rolled texture. The same set of constitutive model parameters are then used in VPSC to predict the aggregate stress-strain response and total dislocation densities. For these VPSC simulations, the interaction parameter governing the interaction between the grain and the effective medium in the Eshelby inclusion formalism, and a scalar parameter representative of the distribution of intragranular stresses within a grain, are used to calibrate the VPSC predictions in order to match the predictions of the ρ-CP model. A parametric study is performed to understand the effect of these two parameters on the VPSC predictions. Further, simulations are also performed for a random untextured polycrystal to identify the corresponding VPSC simulation parameters for predicting a similar response as the ρ-CP model. The novelty of the work is in that the same set of constitutive models and associated parameters have been implemented in VPSC and ρ-CP to predict similar aggregate stress-strain response and total dislocation densities. This finite element-calibrated effective medium crystal plasticity approach reduces the computational time by at least two orders of magnitude and represents an advance towards the development of multiscale crystal plasticity modeling tools.
{"title":"A Dislocation Density-Based Crystal Plasticity Constitutive Model: Comparison of VPSC Effective Medium Predictions with ρ-CP Finite Element Predictions","authors":"A. Patra, C N Tomé","doi":"10.1088/1361-651x/ad3e99","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3e99","url":null,"abstract":"\u0000 This work presents a dislocation density-based crystal plasticity constitutive model for glide kinetics, strengthening and dislocation density evolution, implemented in the effective medium-based Visco-Plastic Self Consistent (VPSC) framework and the spatially resolved, ρ-CP crystal plasticity finite element framework. Additionally, a distribution of intragranular stresses is introduced in the VPSC framework, instead of the conventionally used mean value of grain stress for effective medium calculations. The ρ-CP model is first calibrated to predict the mechanical response of a bcc ferritic steel with an initial rolled texture. The same set of constitutive model parameters are then used in VPSC to predict the aggregate stress-strain response and total dislocation densities. For these VPSC simulations, the interaction parameter governing the interaction between the grain and the effective medium in the Eshelby inclusion formalism, and a scalar parameter representative of the distribution of intragranular stresses within a grain, are used to calibrate the VPSC predictions in order to match the predictions of the ρ-CP model. A parametric study is performed to understand the effect of these two parameters on the VPSC predictions. Further, simulations are also performed for a random untextured polycrystal to identify the corresponding VPSC simulation parameters for predicting a similar response as the ρ-CP model. The novelty of the work is in that the same set of constitutive models and associated parameters have been implemented in VPSC and ρ-CP to predict similar aggregate stress-strain response and total dislocation densities. This finite element-calibrated effective medium crystal plasticity approach reduces the computational time by at least two orders of magnitude and represents an advance towards the development of multiscale crystal plasticity modeling tools.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140699304","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 : 2024-04-15DOI: 10.1088/1361-651x/ad3e97
Bambang Mulyo Raharjo, Budhy Kurniawan, Bambang Soegijono, D. R. Munazat, Dhawud Sabilur Razaq, E. Suprayoga
Conducting optimization calculations for thermoelectric performance can be beneficial in guiding the direction of further experimental work. In our study, we utilize a combination of the first principle, Boltzmann transport and restructured single parabolic band model to investigate the half-doped semiconductors based on manganite. Ca0.5La0.5-xBixMnO3 (x = 0, 0.25) as samples shows the power factor (PF) optimum value of 30% and 69% for x = 0 and 0.25, respectively at a temperature of 800 K. In addition, both samples show two to three orders of magnitude smaller lattice thermal conductivity than their electronic thermal conductivity. This excludes complex phononic transport mechanisms from the calculation of the figure of merit (ZT). The ZT calculations of CLMO and CLBMO are corrected by the ratio of the transport relaxation time of electrical conductivity to the transport relaxation time of electronic thermal conductivity by the Lorenz number, resulting in ZT values of 0.063 and 0.327 at a temperature of 800 K, respectively.
{"title":"Thermoelectric optimization using first principles calculation and single parabolic band model: a case of Ca0.5La0.5-xBixMnO3 (x = 0, 0.25)","authors":"Bambang Mulyo Raharjo, Budhy Kurniawan, Bambang Soegijono, D. R. Munazat, Dhawud Sabilur Razaq, E. Suprayoga","doi":"10.1088/1361-651x/ad3e97","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3e97","url":null,"abstract":"\u0000 Conducting optimization calculations for thermoelectric performance can be beneficial in guiding the direction of further experimental work. In our study, we utilize a combination of the first principle, Boltzmann transport and restructured single parabolic band model to investigate the half-doped semiconductors based on manganite. Ca0.5La0.5-xBixMnO3 (x = 0, 0.25) as samples shows the power factor (PF) optimum value of 30% and 69% for x = 0 and 0.25, respectively at a temperature of 800 K. In addition, both samples show two to three orders of magnitude smaller lattice thermal conductivity than their electronic thermal conductivity. This excludes complex phononic transport mechanisms from the calculation of the figure of merit (ZT). The ZT calculations of CLMO and CLBMO are corrected by the ratio of the transport relaxation time of electrical conductivity to the transport relaxation time of electronic thermal conductivity by the Lorenz number, resulting in ZT values of 0.063 and 0.327 at a temperature of 800 K, respectively.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140700026","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 : 2024-04-15DOI: 10.1088/1361-651x/ad3e98
Liangwu Dai, Jiawei Gao, Tingqiang Yao
In order to investigate the nanoscale friction mechanism and deformation behavior of nickel-copper bilayer film under rolling scraping, the effects of different factors during friction process such as the translation velocity, rotation velocity, radius of abrasive grain, contact depth, texture direction and crystallographic orientation are analyzed through molecular dynamics methods in terms of contact force, atomic lattice structure, internal substrate dislocation, kinetic energy and temperature. Results show that the contact force increases with the increase of the translation velocity or the decrease of the rotation velocity. Abrasive grains in a purely rolling state cause the most serious damage to the substrate. The contact force increases with the increase of contact depth or the decrease of abrasive grain radius, the amount of change in temperature and kinetic energy both increase with contact depth and abrasive radius. The crystallographic orientation has a significant effect on rolling scraping process and there is a crystallographic orientation with the minimum contact force. The degrees of substrate dislocation and the numbers of lattice reconstruction atoms under different factors and levels vary widely.
{"title":"Molecular dynamics simulations into rolling scraping of nickel-copper bilayer film","authors":"Liangwu Dai, Jiawei Gao, Tingqiang Yao","doi":"10.1088/1361-651x/ad3e98","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3e98","url":null,"abstract":"\u0000 In order to investigate the nanoscale friction mechanism and deformation behavior of nickel-copper bilayer film under rolling scraping, the effects of different factors during friction process such as the translation velocity, rotation velocity, radius of abrasive grain, contact depth, texture direction and crystallographic orientation are analyzed through molecular dynamics methods in terms of contact force, atomic lattice structure, internal substrate dislocation, kinetic energy and temperature. Results show that the contact force increases with the increase of the translation velocity or the decrease of the rotation velocity. Abrasive grains in a purely rolling state cause the most serious damage to the substrate. The contact force increases with the increase of contact depth or the decrease of abrasive grain radius, the amount of change in temperature and kinetic energy both increase with contact depth and abrasive radius. The crystallographic orientation has a significant effect on rolling scraping process and there is a crystallographic orientation with the minimum contact force. The degrees of substrate dislocation and the numbers of lattice reconstruction atoms under different factors and levels vary widely.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140699678","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 : 2024-04-15DOI: 10.1088/1361-651x/ad3e9a
Hua Tong, Yue Yang, Y. Liu, Xiaowen Wang, Yiyao Luo, Hu Zhang, Dongbi Mao
Diamond, possessing high hardness and chemical stability, finds wide-ranging applications across various industries. However, during the friction process, a graphitization phenomenon may occur, which changes the mechanical properties of the diamond. In this study, molecular dynamics simulation was performed using SiC ball to investigate the influence of indentation depth and temperature on the graphitization transition of the diamond surface. The results showed that the dominant factor affecting the sp2 hybridization ratio during the indentation process was stress, while the temperature was the dominant factor during sliding. The results of this study can be used to understand the friction and wear behavior of diamonds and SiC ball and provide theoretical references for the industrial application of diamonds.
{"title":"Exploring the evolution mechanisms of indentation and scratching on diamond structural transformation based on molecular dynamics","authors":"Hua Tong, Yue Yang, Y. Liu, Xiaowen Wang, Yiyao Luo, Hu Zhang, Dongbi Mao","doi":"10.1088/1361-651x/ad3e9a","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3e9a","url":null,"abstract":"\u0000 Diamond, possessing high hardness and chemical stability, finds wide-ranging applications across various industries. However, during the friction process, a graphitization phenomenon may occur, which changes the mechanical properties of the diamond. In this study, molecular dynamics simulation was performed using SiC ball to investigate the influence of indentation depth and temperature on the graphitization transition of the diamond surface. The results showed that the dominant factor affecting the sp2 hybridization ratio during the indentation process was stress, while the temperature was the dominant factor during sliding. The results of this study can be used to understand the friction and wear behavior of diamonds and SiC ball and provide theoretical references for the industrial application of diamonds.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140703422","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}
In this work, the HfB2 anisotropic surface stability, and the adsorption and diffusion behavior of oxygen molecule on the most likely exposed HfB2 surface were investigated based on density functional theory. The study found that the HfB2(0001) surface terminated by Hf (labeled as: Hf-(0001)) is more stable and more likely interact with oxygen. By rotating the oxygen molecule orientation and changing the adsorption site, all possible high and low-symmetry adsorption configurations are considered. The results show that the low symmetry structure is unstable, and eventually turn into the high symmetry ones. For the highly symmetric structures, oxygen molecule tends to be adsorbed in parallel, and the dissociated oxygen molecule tends to be located at the bridge and hollow site of the Hf-(0001) surface, and there is no energy barrier to this process. Charge density difference and Partial density of states proved that three absorbed structures present similar electronic interaction characteristics, and oxygen adsorption mainly affects the Hf atom at the outmost layer of the Hf-(0001) plane. Oxygen atoms bind to the Hf-(0001) surface mainly in the form of ionic bonds and covalent bonds, originating from the orbital hybridization of O-p and Hf-d. The oxidation of HfB2 starts from the interaction between oxygen and Hf.
{"title":"A First-principles study of HfB2 anisotropic surface stability and its oxygen adsorption behavior","authors":"G. Cheng, Shengzhu Cao, Zhenzhen Zhang, Yuqing Xiong, Hui Zhou, Yanchun He, Kaifeng Zhang, Hengjiao Gao","doi":"10.1088/1361-651x/ad3cfe","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3cfe","url":null,"abstract":"\u0000 In this work, the HfB2 anisotropic surface stability, and the adsorption and diffusion behavior of oxygen molecule on the most likely exposed HfB2 surface were investigated based on density functional theory. The study found that the HfB2(0001) surface terminated by Hf (labeled as: Hf-(0001)) is more stable and more likely interact with oxygen. By rotating the oxygen molecule orientation and changing the adsorption site, all possible high and low-symmetry adsorption configurations are considered. The results show that the low symmetry structure is unstable, and eventually turn into the high symmetry ones. For the highly symmetric structures, oxygen molecule tends to be adsorbed in parallel, and the dissociated oxygen molecule tends to be located at the bridge and hollow site of the Hf-(0001) surface, and there is no energy barrier to this process. Charge density difference and Partial density of states proved that three absorbed structures present similar electronic interaction characteristics, and oxygen adsorption mainly affects the Hf atom at the outmost layer of the Hf-(0001) plane. Oxygen atoms bind to the Hf-(0001) surface mainly in the form of ionic bonds and covalent bonds, originating from the orbital hybridization of O-p and Hf-d. The oxidation of HfB2 starts from the interaction between oxygen and Hf.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140718282","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 : 2024-04-05DOI: 10.1088/1361-651x/ad3b28
Soumia Hamdani, Saad Abdeslam, A. Hartmaier, R. Janisch
Semi-coherent interfaces can have a strong influence on the mechanical behavior of bilayer systems, which is seen very clearly under indentation conditions where a well-defined plastic zone interacts directly with the interface. The main aim of this work is to study the influence of a semi-coherent bcc/bcc interface in the V/Fe bilayer system with molecular dynamics (MD) simulations. In particular, the influence of the V layer thicknesses on the apparent hardness of the bilayer system is investigated. Our results show that the deformation behavior of pure V and pure Fe resulting from the MD simulations is in good agreement with the literature. Moreover, the MD simulations reveal a significant enhancement of the hardness of V/Fe bilayer system for thinner vanadium layers, resulting from the crucial role of the semi-coherent interface as a barrier to dislocation propagation. This is seen from a detailed analysis of the interaction of mobile dislocations in the plastic zone with misfit dislocations in the interface. Our work shows that dislocation pile-ups at the interface and formation of horizontal shear loops are two key mechanisms dominating the rate and magnitude of plastic deformation and thus contributes to our understanding of mechanical behavior of bilayer systems with semi-coherent interfaces.
半相干界面对双层体系的机械行为有很大的影响，这在压痕条件下表现得非常明显，在压痕条件下，一个定义明确的塑性区直接与界面相互作用。这项工作的主要目的是通过分子动力学（MD）模拟研究 V/Fe 双层体系中的半相干 bcc/bcc 界面的影响。特别是研究了 V 层厚度对双层体系表观硬度的影响。我们的研究结果表明，MD 模拟得出的纯 V 和纯铁的变形行为与文献报道十分吻合。此外，MD 模拟还显示，钒层越薄，钒/铁双层体系的硬度就越高，这是因为半相干界面在阻碍位错传播方面发挥了关键作用。通过详细分析塑性区移动位错与界面错位错之间的相互作用，我们可以发现这一点。我们的研究表明，界面上的位错堆积和水平剪切环的形成是主导塑性变形速度和幅度的两个关键机制，因此有助于我们理解具有半相干界面的双层体系的力学行为。
{"title":"Atomistic simulation of the influence of semi-coherent interfaces in the V/Fe bilayer system on plastic deformation during nanoindentation","authors":"Soumia Hamdani, Saad Abdeslam, A. Hartmaier, R. Janisch","doi":"10.1088/1361-651x/ad3b28","DOIUrl":"https://doi.org/10.1088/1361-651x/ad3b28","url":null,"abstract":"\u0000 Semi-coherent interfaces can have a strong influence on the mechanical behavior of bilayer systems, which is seen very clearly under indentation conditions where a well-defined plastic zone interacts directly with the interface. The main aim of this work is to study the influence of a semi-coherent bcc/bcc interface in the V/Fe bilayer system with molecular dynamics (MD) simulations. In particular, the influence of the V layer thicknesses on the apparent hardness of the bilayer system is investigated. Our results show that the deformation behavior of pure V and pure Fe resulting from the MD simulations is in good agreement with the literature. Moreover, the MD simulations reveal a significant enhancement of the hardness of V/Fe bilayer system for thinner vanadium layers, resulting from the crucial role of the semi-coherent interface as a barrier to dislocation propagation. This is seen from a detailed analysis of the interaction of mobile dislocations in the plastic zone with misfit dislocations in the interface. Our work shows that dislocation pile-ups at the interface and formation of horizontal shear loops are two key mechanisms dominating the rate and magnitude of plastic deformation and thus contributes to our understanding of mechanical behavior of bilayer systems with semi-coherent interfaces.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140738287","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 : 2024-04-03DOI: 10.1088/1361-651x/ad39fe
Can Zhang, Mingxing Shi
This study uses molecular dynamics simulations to explore the mechanical properties of a nano-twinned copper-nickel alloy through nano-indentations. The effects from twin boundary angle and spacing on the alloy’s behavior are mainly focused on. It is found that the plastic deformation process is primarily driven by dislocation generations, slips, and interactions between dislocations and twin boundaries, all combined affecting the alloy’s hardness. Significant findings include: (1) hardness initially decreases and then increases with twin boundary angle increasing; when the twin boundary spacing is greater than 1.25 nm, hardness can be predicted by using a simple proposed model; (2) dislocation density experiences significant variations, leveling off at an indentation depth around 1.0 nm; (3) when twin boundary spacing exceeds 1.25 nm, plastic deformation is dominated by dislocation nucleation, slips, and interactions with twin boundaries, while smaller spacings lead to twin boundary migration and the presence of independent dislocation loops, giving rise to force fluctuations along indentation process.
{"title":"Indentation-induced plastic behavior of nanotwinned CuNi alloy: an atomic simulation","authors":"Can Zhang, Mingxing Shi","doi":"10.1088/1361-651x/ad39fe","DOIUrl":"https://doi.org/10.1088/1361-651x/ad39fe","url":null,"abstract":"\u0000 This study uses molecular dynamics simulations to explore the mechanical properties of a nano-twinned copper-nickel alloy through nano-indentations. The effects from twin boundary angle and spacing on the alloy’s behavior are mainly focused on. It is found that the plastic deformation process is primarily driven by dislocation generations, slips, and interactions between dislocations and twin boundaries, all combined affecting the alloy’s hardness. Significant findings include: (1) hardness initially decreases and then increases with twin boundary angle increasing; when the twin boundary spacing is greater than 1.25 nm, hardness can be predicted by using a simple proposed model; (2) dislocation density experiences significant variations, leveling off at an indentation depth around 1.0 nm; (3) when twin boundary spacing exceeds 1.25 nm, plastic deformation is dominated by dislocation nucleation, slips, and interactions with twin boundaries, while smaller spacings lead to twin boundary migration and the presence of independent dislocation loops, giving rise to force fluctuations along indentation process.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140748171","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 : 2024-03-08DOI: 10.1088/1361-651x/ad2d67
Yunpeng Gao, Xiangguo Zeng, Minghua Chi
Repairing metal micro-defects at the atomic level is very challenging due to their random dispersion and difficulty in identification. At the same time, the interaction of hydrogen with metal may cause hydrogen damage or embrittlement, endangering structural safety. As a result, it is critical to speed up the dehydrogenation of hydrogen-containing materials. The applied electric field can repair the vacancy defects of the material and accelerate the dehydrogenation of the hydrogen-containing metal. The influence of the external environment on the diffusion coefficient of hydrogen in polycrystalline metals was researched using molecular dynamics in this article, and the mechanism of hydrogen diffusion was investigated. Simultaneously, the mechanical characteristics of Fe3Cr alloy were compared during typical heat treatment and electrical treatment. The effect of temperature, electric field strength, and electric field direction on the diffusion coefficient was investigated using orthogonal test analysis. The results demonstrate that temperature and electric field strength have a significant impact on the diffusion coefficient. The atom vibrates violently as the temperature rises, breaking past the diffusion barrier and completing the atomic transition. The addition of the electric field adds extra free energy, decreases the atom’s activation energy, and ultimately enhances the atom’s diffusion coefficient. The repair impact of vacancy defects under electrical treatment is superior to that of typical annealing treatment for polycrystalline Fe3Cr alloy. The electric field can cause the dislocation to migrate, increasing the metal’s toughness and plasticity. This research serves as a useful reference for the electrical treatment of metal materials and offers a method for the quick dehydrogenation of hydrogen-containing materials.
{"title":"Applied electric field to repair metal defects and accelerate dehydrogenation","authors":"Yunpeng Gao, Xiangguo Zeng, Minghua Chi","doi":"10.1088/1361-651x/ad2d67","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2d67","url":null,"abstract":"Repairing metal micro-defects at the atomic level is very challenging due to their random dispersion and difficulty in identification. At the same time, the interaction of hydrogen with metal may cause hydrogen damage or embrittlement, endangering structural safety. As a result, it is critical to speed up the dehydrogenation of hydrogen-containing materials. The applied electric field can repair the vacancy defects of the material and accelerate the dehydrogenation of the hydrogen-containing metal. The influence of the external environment on the diffusion coefficient of hydrogen in polycrystalline metals was researched using molecular dynamics in this article, and the mechanism of hydrogen diffusion was investigated. Simultaneously, the mechanical characteristics of Fe<sub>3</sub>Cr alloy were compared during typical heat treatment and electrical treatment. The effect of temperature, electric field strength, and electric field direction on the diffusion coefficient was investigated using orthogonal test analysis. The results demonstrate that temperature and electric field strength have a significant impact on the diffusion coefficient. The atom vibrates violently as the temperature rises, breaking past the diffusion barrier and completing the atomic transition. The addition of the electric field adds extra free energy, decreases the atom’s activation energy, and ultimately enhances the atom’s diffusion coefficient. The repair impact of vacancy defects under electrical treatment is superior to that of typical annealing treatment for polycrystalline Fe<sub>3</sub>Cr alloy. The electric field can cause the dislocation to migrate, increasing the metal’s toughness and plasticity. This research serves as a useful reference for the electrical treatment of metal materials and offers a method for the quick dehydrogenation of hydrogen-containing materials.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314160","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 : 2024-03-08DOI: 10.1088/1361-651x/ad2d69
Qingyu Hou, Mude Qi, Cong Li
The new magnetic mechanism and optical properties of Ga vacancies and Hi interstitial in the GaN: Be/Mg/Ca system have not been fully understood, and the use of first principles can solve this problem. The effect of point defects on the magnetic mechanism and optical properties of the GaN: Be/Mg/Ca system was investigated using the first nature principle of the hybridized generalized HSE06 method. Results show that all doped systems have N2− ions in addition to N3− ions, and N2− ions have the dual property of itinerant electrons in the off-domain (donor) and of local electrons (acceptor). The magnetism of magnetic doped systems is generated by the hybrid coupling of Ga4s and N2− 2p states. In comparison with the Ga34MN36 (M = Be/Ca) system, the magnetic moments of Ga34MHiN36 (M = Be/Ca) system are reduced after doping with Hi interstitial. The magnetic properties of the Ga34MgN36 system can be regulated by the presence or absence of Hi interstitial, which is advantageous as a magnetic switch. The absorption spectral distribution of the Ga34MgHiN36 system extends to the mid-infrared optical region. This material has some reference value as infrared thermophotovoltaic cells, infrared photodetectors, or infrared semiconductor lasers.
人们对 GaN：Be/Mg/Ca 体系中 Ga 空位和 Hi 间隙的新磁机制和光学性质还没有完全了解，而利用第一性原理可以解决这个问题。利用杂化广义 HSE06 方法的第一性原理研究了点缺陷对 GaN：Be/Mg/Ca 体系的磁机制和光学性质的影响。结果表明，所有掺杂体系中除了 N3- 离子外，还有 N2- 离子，N2- 离子具有离域巡回电子（供体）和局部电子（受体）的双重特性。掺磁系统的磁性是由 Ga4s 和 N2- 2p 态的混合耦合产生的。与 Ga34MN36（M = Be/Ca）体系相比，Ga34MHiN36（M = Be/Ca）体系在掺杂 Hi 中间体后磁矩减小。Ga34MgN36 体系的磁性能可以通过 Hi 中间体的存在或不存在来调节，这对于磁开关来说是非常有利的。Ga34MgHiN36 系统的吸收光谱分布延伸至中红外光区。这种材料作为红外热光电池、红外光探测器或红外半导体激光器具有一定的参考价值。
{"title":"First-principles study on the effect of point defects on the magnetic new mechanism and optical properties of the GaN:Be/Mg/Ca system","authors":"Qingyu Hou, Mude Qi, Cong Li","doi":"10.1088/1361-651x/ad2d69","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2d69","url":null,"abstract":"The new magnetic mechanism and optical properties of Ga vacancies and H<sub>i</sub> interstitial in the GaN: Be/Mg/Ca system have not been fully understood, and the use of first principles can solve this problem. The effect of point defects on the magnetic mechanism and optical properties of the GaN: Be/Mg/Ca system was investigated using the first nature principle of the hybridized generalized HSE06 method. Results show that all doped systems have N<sup>2−</sup> ions in addition to N<sup>3−</sup> ions, and N<sup>2−</sup> ions have the dual property of itinerant electrons in the off-domain (donor) and of local electrons (acceptor). The magnetism of magnetic doped systems is generated by the hybrid coupling of Ga4s and N<sup>2−</sup> 2p states. In comparison with the Ga<sub>34</sub>MN<sub>36</sub> (M = Be/Ca) system, the magnetic moments of Ga<sub>34</sub>MH<sub>i</sub>N<sub>36</sub> (M = Be/Ca) system are reduced after doping with H<sub>i</sub> interstitial. The magnetic properties of the Ga<sub>34</sub>MgN<sub>36</sub> system can be regulated by the presence or absence of H<sub>i</sub> interstitial, which is advantageous as a magnetic switch. The absorption spectral distribution of the Ga<sub>34</sub>MgH<sub>i</sub>N<sub>36</sub> system extends to the mid-infrared optical region. This material has some reference value as infrared thermophotovoltaic cells, infrared photodetectors, or infrared semiconductor lasers.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314317","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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