Pub Date : 2024-08-28DOI: 10.1088/1361-651x/ad6fbe
Suman Sarkar, Papiya Debnath, Debashis De, Manash Chanda
The sensing performances of the Rhenium (Re) doped Tungsten Diselenide (WSe2) monolayer for detecting small gas molecules such as carbon monoxide (CO), acetylene (C2H2), and ethylene (C2H4) have been analyzed in this paper. Density functional theory and non-equilibrium Green’s function have been used to examine the electrical and geometric structures of re-adorned WSe2 monolayer when subjected to dissolved gas analysis gases in the transformer oil. Hence, the electrochemical characteristics like Band diagram and density of states are detailed. Adsorption systems’ recovery capabilities, Mulliken population, and adsorption energy have been examined to determine their stability. Studies also show that Re-doped WSe2 monolayer exerts deformation and as a result, the band gap narrowed down. At ambient temperature (273 K–300 K), the Re-doped WSe2 exhibits better adsorption of C2H4 over C2H2 and CO as the C2H4 has higher adsorption energy compared to the C2H2 and CO. Besides, V–I characteristics of the Re doped WSe2 layer after adsorption of the CO, C2H2, and C2H4 are detailed which signifies the efficacy of the Re doped WSe2 monolayer.
{"title":"DFT analysis of Re-modified WSe2 monolayers for adsorption of CO, C2H2, and C2H4","authors":"Suman Sarkar, Papiya Debnath, Debashis De, Manash Chanda","doi":"10.1088/1361-651x/ad6fbe","DOIUrl":"https://doi.org/10.1088/1361-651x/ad6fbe","url":null,"abstract":"The sensing performances of the Rhenium (Re) doped Tungsten Diselenide (WSe<sub>2</sub>) monolayer for detecting small gas molecules such as carbon monoxide (CO), acetylene (C<sub>2</sub>H<sub>2</sub>), and ethylene (C<sub>2</sub>H<sub>4</sub>) have been analyzed in this paper. Density functional theory and non-equilibrium Green’s function have been used to examine the electrical and geometric structures of re-adorned WSe<sub>2</sub> monolayer when subjected to dissolved gas analysis gases in the transformer oil. Hence, the electrochemical characteristics like Band diagram and density of states are detailed. Adsorption systems’ recovery capabilities, Mulliken population, and adsorption energy have been examined to determine their stability. Studies also show that Re-doped WSe<sub>2</sub> monolayer exerts deformation and as a result, the band gap narrowed down. At ambient temperature (273 K–300 K), the Re-doped WSe<sub>2</sub> exhibits better adsorption of C<sub>2</sub>H<sub>4</sub> over C<sub>2</sub>H<sub>2</sub> and CO as the C<sub>2</sub>H<sub>4</sub> has higher adsorption energy compared to the C<sub>2</sub>H<sub>2</sub> and CO. Besides, <italic toggle=\"yes\">V–I</italic> characteristics of the Re doped WSe<sub>2</sub> layer after adsorption of the CO, C<sub>2</sub>H<sub>2</sub>, and C<sub>2</sub>H<sub>4</sub> are detailed which signifies the efficacy of the Re doped WSe<sub>2</sub> monolayer.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"53 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225375","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 paper introduces a comprehensive computational framework, comprising a finite deformation crystal inelasticity constitutive model and phase field model, for modeling crack growth in superelastic nitinol polycrystalline microstructures. The crystal inelasticity model represents crystal stretching and lattice rotation from elastic mechanisms, as well as local inelastic deformation due to austenite-martensite phase transformation. The phase field formulation decomposes the Helmholtz free energy density into stored elastic energy, phase transformation energy, and crack surface energy components. The elastic energy accounts for tension-compression asymmetry with the formation of the crack through a spectral decomposition. Kinetic Monte Carlo simulations generate equilibrium area fractions of different surface orientations, which serve as weights for the surface energy. An adaptive wavelet-enhanced hierarchical finite element (FE) model is introduced to alleviate high computational overhead in phase field crack simulations. Simulations with the coupled inelasticity phase field model are conducted under various loading conditions including Mode-I tension, a quasi-static Kalthoff experiment, and cyclic loading of polycrystalline microstructures. Crack propagation is effectively predicted by this model, providing valuable insights into the material mechanical behavior with growing cracks.
本文介绍了一种综合计算框架，包括有限变形晶体非弹性结构模型和相场模型，用于模拟超弹性镍钛诺多晶微结构中的裂纹生长。晶体非弹性模型表示了弹性机制引起的晶体拉伸和晶格旋转，以及奥氏体-马氏体相变引起的局部非弹性变形。相场公式将亥姆霍兹自由能密度分解为储存的弹性能、相变能和裂纹表面能。弹性能通过频谱分解反映了裂纹形成时拉伸与压缩的不对称。动力学蒙特卡洛模拟产生了不同表面取向的平衡面积分数，作为表面能的权重。引入了自适应小波增强分层有限元（FE）模型，以减轻相场裂纹模拟的高计算开销。利用耦合非弹性相场模型在各种加载条件下进行了模拟，包括模式 I 拉伸、准静态 Kalthoff 实验以及多晶微结构的循环加载。该模型有效地预测了裂纹的扩展，为了解材料在裂纹扩展时的机械行为提供了宝贵的见解。
{"title":"A coupled crystal inelasticity-phase field model for crack growth in polycrystalline nitinol microstructures","authors":"Thirupathi Maloth, Pheobe Appel, Jonah Erlebacher, Somnath Ghosh","doi":"10.1088/1361-651x/ad6fbf","DOIUrl":"https://doi.org/10.1088/1361-651x/ad6fbf","url":null,"abstract":"This paper introduces a comprehensive computational framework, comprising a finite deformation crystal inelasticity constitutive model and phase field model, for modeling crack growth in superelastic nitinol polycrystalline microstructures. The crystal inelasticity model represents crystal stretching and lattice rotation from elastic mechanisms, as well as local inelastic deformation due to austenite-martensite phase transformation. The phase field formulation decomposes the Helmholtz free energy density into stored elastic energy, phase transformation energy, and crack surface energy components. The elastic energy accounts for tension-compression asymmetry with the formation of the crack through a spectral decomposition. Kinetic Monte Carlo simulations generate equilibrium area fractions of different surface orientations, which serve as weights for the surface energy. An adaptive wavelet-enhanced hierarchical finite element (FE) model is introduced to alleviate high computational overhead in phase field crack simulations. Simulations with the coupled inelasticity phase field model are conducted under various loading conditions including Mode-I tension, a quasi-static Kalthoff experiment, and cyclic loading of polycrystalline microstructures. Crack propagation is effectively predicted by this model, providing valuable insights into the material mechanical behavior with growing cracks.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"114 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225376","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 : 2024-08-27DOI: 10.1088/1361-651x/ad6ea9
R M Meftakhutdinov
The structural, cohesive and magnetic properties of a symmetric Σ3(70.53)[011](11-1) tilt grain boundary in pure bcc iron and with commonly used alloying elements (Si, Co, Mn, Ti, Cu, Mo, Nb, V, Cr and Ni) by means of density functional theory calculations are studied. Solubility and segregation energies were calculated for different positions of dissolved atoms. Calculations show a tendency for impurities to segregate near the boundary. It was found that the substituting Co, Cu and Ni in the layer adjacent to the boundary have an embrittling effect, while other atoms enhance the cohesion of the grains. Magnetic moments on GB atoms are significantly higher than those on bulk atoms.
{"title":"First-principles study of the interaction of solutes with ∑3(11-1) symmetric tilt grain boundaries in α-Fe","authors":"R M Meftakhutdinov","doi":"10.1088/1361-651x/ad6ea9","DOIUrl":"https://doi.org/10.1088/1361-651x/ad6ea9","url":null,"abstract":"The structural, cohesive and magnetic properties of a symmetric Σ3(70.53)[011](11-1) tilt grain boundary in pure bcc iron and with commonly used alloying elements (Si, Co, Mn, Ti, Cu, Mo, Nb, V, Cr and Ni) by means of density functional theory calculations are studied. Solubility and segregation energies were calculated for different positions of dissolved atoms. Calculations show a tendency for impurities to segregate near the boundary. It was found that the substituting Co, Cu and Ni in the layer adjacent to the boundary have an embrittling effect, while other atoms enhance the cohesion of the grains. Magnetic moments on GB atoms are significantly higher than those on bulk atoms.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"219 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198946","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 : 2024-08-13DOI: 10.1088/1361-651x/ad691d
Murali Uddagiri, Marvin Tegeler, Ingo Steinbach
One of the long-standing problems in the phase field, namely, combining the principles of thermodynamics and capillarity with the numerical aspects of interface propagation in simulations, is re-investigated. Numerical schemes are discussed which allow for stable simulations with arbitrary driving forces, considering or excluding capillarity. We re-investigate a classical stabilization scheme that decouples interface stabilization from curvature evaluation, ensuring stable simulations even under large driving forces. A novel mathematical analysis gives a rigorous estimate for the time stepping and a numerical value of the required stabilization strength. The proposed stabilization scheme is benchmarked for three-dimensional dendritic growth under directional solidification conditions for different solidification speeds.
{"title":"Interface stabilization and propagation in phase field models of solidification: resolving the issue of large driving forces","authors":"Murali Uddagiri, Marvin Tegeler, Ingo Steinbach","doi":"10.1088/1361-651x/ad691d","DOIUrl":"https://doi.org/10.1088/1361-651x/ad691d","url":null,"abstract":"One of the long-standing problems in the phase field, namely, combining the principles of thermodynamics and capillarity with the numerical aspects of interface propagation in simulations, is re-investigated. Numerical schemes are discussed which allow for stable simulations with arbitrary driving forces, considering or excluding capillarity. We re-investigate a classical stabilization scheme that decouples interface stabilization from curvature evaluation, ensuring stable simulations even under large driving forces. A novel mathematical analysis gives a rigorous estimate for the time stepping and a numerical value of the required stabilization strength. The proposed stabilization scheme is benchmarked for three-dimensional dendritic growth under directional solidification conditions for different solidification speeds.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"69 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198947","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 : 2024-08-11DOI: 10.1088/1361-651x/ad6a74
Yuncui Chen, Baocheng Zhou, Huibin Zhu, Haiyan Li, Ruicheng Feng, Hui Cao and Chunli Lei
TiAl alloys are favored by the aerospace industry due to its excellent mechanical properties. However, its intrinsic brittleness, the use of conventional cutting (CC) process leads to the problems of high cutting force and high cutting temperature, which in turn affects the machined surface quality. Ultrasonic elliptical vibratory cutting (UEVC) has been proved to be an effective method to improve the surface quality and reduce the subsurface damage of difficult-to-machine materials. This paper compares the effects of CC and UEVC processes on cutting forces and subsurface damage based on molecular dynamics simulation methods, and the effects of elliptical vibration frequencies and amplitude ratios (AR) on surface morphology, roughness, and subsurface damage are investigated. The results show that the cutting force and subsurface damage in the UEVC process are reduced compared with that in the CC. Due to the vibration frequency, the subsurface damage is mainly dominated by atomic clusters, and both surface and subsurface masses show an optimization trend as the vibration frequency decreases. In terms of the AR, the surface quality is better at an AR of 2/3, with less activation of immovable dislocations, and the degree of subsurface damage decreases as the AR increases, and a relatively stable defective structure emerges when the AR is 1/2. The simulation results facilitate an atomic-scale comprehension of the removal mechanism of UEVC and further provide a theoretical foundation for the surface mass and subsurface damage mechanism and optimization of vibrational parameters of UEVC single crystal γ-TiAl alloy.
钛铝合金因其优异的机械性能而受到航空航天工业的青睐。然而，由于其本身的脆性，使用传统切削（CC）工艺会导致切削力大、切削温度高的问题，进而影响加工表面质量。超声波椭圆振动切割（UEVC）已被证明是改善难加工材料表面质量和减少表面下损伤的有效方法。本文基于分子动力学模拟方法，比较了 CC 和 UEVC 工艺对切削力和表面下损伤的影响，并研究了椭圆振动频率和振幅比 (AR) 对表面形态、粗糙度和表面下损伤的影响。结果表明，与 CC 工艺相比，UEVC 工艺的切削力和表面下损伤都有所降低。由于振动频率的原因，次表层损伤主要以原子团为主，随着振动频率的降低，表面和次表层质量都呈现出优化趋势。就 AR 而言，当 AR 为 2/3 时，表面质量较好，不可移动位错的活化程度较低；随着 AR 的增大，次表层损伤程度减小；当 AR 为 1/2 时，出现了相对稳定的缺陷结构。模拟结果有助于在原子尺度上理解 UEVC 的去除机制，并进一步为 UEVC 单晶 γ-TiAl 合金的表面质量和次表面损伤机制以及振动参数的优化提供了理论基础。
{"title":"Effect of UEVC parameters on cutting surface quality and subsurface damage of single crystal γ-TiAl alloy via atomic simulation","authors":"Yuncui Chen, Baocheng Zhou, Huibin Zhu, Haiyan Li, Ruicheng Feng, Hui Cao and Chunli Lei","doi":"10.1088/1361-651x/ad6a74","DOIUrl":"https://doi.org/10.1088/1361-651x/ad6a74","url":null,"abstract":"TiAl alloys are favored by the aerospace industry due to its excellent mechanical properties. However, its intrinsic brittleness, the use of conventional cutting (CC) process leads to the problems of high cutting force and high cutting temperature, which in turn affects the machined surface quality. Ultrasonic elliptical vibratory cutting (UEVC) has been proved to be an effective method to improve the surface quality and reduce the subsurface damage of difficult-to-machine materials. This paper compares the effects of CC and UEVC processes on cutting forces and subsurface damage based on molecular dynamics simulation methods, and the effects of elliptical vibration frequencies and amplitude ratios (AR) on surface morphology, roughness, and subsurface damage are investigated. The results show that the cutting force and subsurface damage in the UEVC process are reduced compared with that in the CC. Due to the vibration frequency, the subsurface damage is mainly dominated by atomic clusters, and both surface and subsurface masses show an optimization trend as the vibration frequency decreases. In terms of the AR, the surface quality is better at an AR of 2/3, with less activation of immovable dislocations, and the degree of subsurface damage decreases as the AR increases, and a relatively stable defective structure emerges when the AR is 1/2. The simulation results facilitate an atomic-scale comprehension of the removal mechanism of UEVC and further provide a theoretical foundation for the surface mass and subsurface damage mechanism and optimization of vibrational parameters of UEVC single crystal γ-TiAl alloy.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"24 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941790","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 : 2024-08-11DOI: 10.1088/1361-651x/ad691b
O C Şen and R Janisch
The fracture behavior of the Ti–Al alloy is significantly affected by its nano-lamellar structure. However, further investigation is still required to fully comprehend how the initial crack configuration influences the lamellar Ti–Al’s deformation behavior. Although molecular dynamics simulations are a great way to study crack-tip interactions in interface-dominated microstructures, the design of the simulation can have an impact on the behavior that is predicted. To shed light on this matter and at the same time to understand the impact of the specific interface structure, a systematic study of crack-tip interface interactions in nano-lamellar two-phase Ti–Al was carried out. The type of interface and crack configuration were varied in these simulations to distinguish between the effects of the microstructure and the crack geometry. Results show that the semi-coherent pseudo twin ( PT) interface is the strongest barrier for crack propagation while the coherent true twin interface ( TT) is the weakest. After a thorough review of the contributing factors, it is evident that the orientation of the crack has a greater impact on its propagation than the aspect ratio of the crack. The stress shielding effectiveness of lamellar interfaces is strongly dependent on the crack configuration. However, regardless of the initial crack set-up, the coherent TT interface appears to be the most effective interface in terms of shielding.
{"title":"Crack configuration influence on fracture behavior and stress shielding: insights from molecular dynamics simulations","authors":"O C Şen and R Janisch","doi":"10.1088/1361-651x/ad691b","DOIUrl":"https://doi.org/10.1088/1361-651x/ad691b","url":null,"abstract":"The fracture behavior of the Ti–Al alloy is significantly affected by its nano-lamellar structure. However, further investigation is still required to fully comprehend how the initial crack configuration influences the lamellar Ti–Al’s deformation behavior. Although molecular dynamics simulations are a great way to study crack-tip interactions in interface-dominated microstructures, the design of the simulation can have an impact on the behavior that is predicted. To shed light on this matter and at the same time to understand the impact of the specific interface structure, a systematic study of crack-tip interface interactions in nano-lamellar two-phase Ti–Al was carried out. The type of interface and crack configuration were varied in these simulations to distinguish between the effects of the microstructure and the crack geometry. Results show that the semi-coherent pseudo twin ( PT) interface is the strongest barrier for crack propagation while the coherent true twin interface ( TT) is the weakest. After a thorough review of the contributing factors, it is evident that the orientation of the crack has a greater impact on its propagation than the aspect ratio of the crack. The stress shielding effectiveness of lamellar interfaces is strongly dependent on the crack configuration. However, regardless of the initial crack set-up, the coherent TT interface appears to be the most effective interface in terms of shielding.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"100 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941789","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 : 2024-08-07DOI: 10.1088/1361-651x/ad691c
Pan Li, Fazhan Wang, Guangyuan Li, Yuan Fan, Zhanwen Chen, Menghui Liu and Hong Wu
In this study, the effects of Bi content and temperature on the mechanical properties of Fe–Bi nanocomposites were investigated using molecular dynamics simulation. The research reveals that the nanocomposite’s shear strength reaches a peak of 3.785 GPa at a Bi content of 0.15%, attributed to the impediment of dislocation movement by twin boundaries during shearing, resulting in a dynamic ‘Hall–Petch’ effect and exceptional shear performance of the material. The abundant twinning induced around Bi phase inclusions introduces orientational disparities within the crystal, leading to grain misalignments, with dislocations in the grains slipping near the twin boundaries. In the nanocomposites, <100> dislocations merely act as initial sites for reactions, reducing their impact on the material’s strength and fracture behavior. The maximum stress decreases with increasing temperature while the magnitude of atomic transformations increases. The proportion of atoms at grain boundaries is higher at higher temperatures, and the arrangement of atoms at grain boundaries is more complex. At a temperature of 100 K, the dislocation density is highest with the smallest variation, forming a reinforced region within the material. The above results have significant implications for the design of environmentally friendly Bi-containing free-cutting steels.
本研究利用分子动力学模拟研究了 Bi 含量和温度对 Fe-Bi 纳米复合材料力学性能的影响。研究发现，当 Bi 含量为 0.15% 时，纳米复合材料的剪切强度达到 3.785 GPa 的峰值，这是由于孪晶边界在剪切过程中阻碍了位错运动，从而产生了动态 "霍尔-佩奇 "效应，使材料具有优异的剪切性能。Bi 相夹杂物周围产生的大量孪晶在晶体内部引入了取向差异，导致晶粒错位，晶粒中的位错在孪晶边界附近滑动。在纳米复合材料中，位错只是作为反应的初始位置，减少了对材料强度和断裂行为的影响。最大应力随着温度的升高而减小，而原子转变的幅度却在增大。温度越高，晶界处的原子比例越高，晶界处的原子排列也越复杂。温度为 100 K 时，位错密度最高，变化最小，在材料内部形成一个强化区域。上述结果对设计环保型含铋易切削钢具有重要意义。
{"title":"Effect of Bi content and temperature on the shear mechanical properties of Fe-Bi nanocomposites: a molecular dynamics study","authors":"Pan Li, Fazhan Wang, Guangyuan Li, Yuan Fan, Zhanwen Chen, Menghui Liu and Hong Wu","doi":"10.1088/1361-651x/ad691c","DOIUrl":"https://doi.org/10.1088/1361-651x/ad691c","url":null,"abstract":"In this study, the effects of Bi content and temperature on the mechanical properties of Fe–Bi nanocomposites were investigated using molecular dynamics simulation. The research reveals that the nanocomposite’s shear strength reaches a peak of 3.785 GPa at a Bi content of 0.15%, attributed to the impediment of dislocation movement by twin boundaries during shearing, resulting in a dynamic ‘Hall–Petch’ effect and exceptional shear performance of the material. The abundant twinning induced around Bi phase inclusions introduces orientational disparities within the crystal, leading to grain misalignments, with dislocations in the grains slipping near the twin boundaries. In the nanocomposites, <100> dislocations merely act as initial sites for reactions, reducing their impact on the material’s strength and fracture behavior. The maximum stress decreases with increasing temperature while the magnitude of atomic transformations increases. The proportion of atoms at grain boundaries is higher at higher temperatures, and the arrangement of atoms at grain boundaries is more complex. At a temperature of 100 K, the dislocation density is highest with the smallest variation, forming a reinforced region within the material. The above results have significant implications for the design of environmentally friendly Bi-containing free-cutting steels.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"25 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941791","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 : 2024-08-04DOI: 10.1088/1361-651x/ad64f3
Linus C Erhard, Daniel Utt, Arne J Klomp and Karsten Albe
Efficient, reliable and easy-to-use structure recognition of atomic environments is essential for the analysis of atomic scale computer simulations. In this work, we train two neuronal network (NN) architectures, namely PointNet and dynamic graph convolutional NN (DG-CNN) using different hyperparameters and training regimes to assess their performance in structure identification tasks of atomistic structure data. We show benchmarks on simple crystal structures, where we can compare against established methods. The approach is subsequently extended to structurally more complex SiO2 phases. By making use of this structure recognition tool, we are able to achieve a deeper understanding of the crystallization process in amorphous SiO2 under shock compression. Lastly, we show how the NN based structure identification workflows can be integrated into OVITO using its python interface.
{"title":"Crystal structure identification with 3D convolutional neural networks with application to high-pressure phase transitions in SiO2","authors":"Linus C Erhard, Daniel Utt, Arne J Klomp and Karsten Albe","doi":"10.1088/1361-651x/ad64f3","DOIUrl":"https://doi.org/10.1088/1361-651x/ad64f3","url":null,"abstract":"Efficient, reliable and easy-to-use structure recognition of atomic environments is essential for the analysis of atomic scale computer simulations. In this work, we train two neuronal network (NN) architectures, namely PointNet and dynamic graph convolutional NN (DG-CNN) using different hyperparameters and training regimes to assess their performance in structure identification tasks of atomistic structure data. We show benchmarks on simple crystal structures, where we can compare against established methods. The approach is subsequently extended to structurally more complex SiO2 phases. By making use of this structure recognition tool, we are able to achieve a deeper understanding of the crystallization process in amorphous SiO2 under shock compression. Lastly, we show how the NN based structure identification workflows can be integrated into OVITO using its python interface.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"14 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941857","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 : 2024-07-23DOI: 10.1088/1361-651x/ad5c85
Adam Fisher, Julie B Staunton, Huan Wu and Peter Brommer
Precipitates in nickel-based superalloys form during heat treatment on a time scale inaccessible to direct molecular dynamics simulation, but can be studied using kinetic Monte Carlo (KMC) modelling. This requires reliable values for the barrier energies separating distinct configurations over the trajectory of the system. In this study, we validate vacancy migration barriers found with the Activation-Relaxation Technique nouveau (ARTn) method in partially ordered Ni75Al25 with a monovacancy using published potentials for the atomic interactions against first-principles methods. In a first step, we confirm that the ARTn barrier energies agree with those determined with the nudged elastic band (NEB) method. As the number of atoms used in those calculations is too great for direct ab initio calculations, we cut the cell size to 255 atoms, thus controlling finite size effects. We then use the plane-wave density functional theory code CASTEP and its inbuilt NEB method in the smaller cells. This provides us with a continuous validation chain from first principles to KMC simulations with interatomic potentials (IPs). We evaluate the barrier energies of five further IPs with NEB, demonstrating that none yields values with sufficient reliability for KMC simulations, with some of them failing completely. This is a first step towards quantifying the errors incurred in KMC simulations of precipitate formation and evolution.
镍基超合金中的沉淀物在热处理过程中形成，其时间尺度无法直接进行分子动力学模拟，但可以使用动力学蒙特卡罗（KMC）建模进行研究。这就需要在系统轨迹上分隔不同构型的势垒能的可靠值。在本研究中，我们利用已公布的原子相互作用势能与第一原理方法，验证了在部分有序的单共价物 Ni75Al25 中通过新活化-松弛技术（ARTn）方法发现的空位迁移势垒。首先，我们确认 ARTn 势垒能与用裸弹带（NEB）方法确定的势垒能一致。由于在这些计算中使用的原子数量过多，无法进行直接的 ab initio 计算，因此我们将单元尺寸缩小到 255 个原子，从而控制了有限尺寸效应。然后，我们在较小的单元中使用平面波密度泛函理论代码 CASTEP 及其内置 NEB 方法。这为我们提供了从第一原理到使用原子间势（IP）进行 KMC 模拟的连续验证链。我们用 NEB 评估了另外五个 IP 的势垒能，结果表明，没有一个 IP 能产生足够可靠的 KMC 模拟值，其中一些 IP 完全失效。这是量化 KMC 模拟沉淀形成和演化所产生误差的第一步。
{"title":"First principles validation of energy barriers in Ni75Al25","authors":"Adam Fisher, Julie B Staunton, Huan Wu and Peter Brommer","doi":"10.1088/1361-651x/ad5c85","DOIUrl":"https://doi.org/10.1088/1361-651x/ad5c85","url":null,"abstract":"Precipitates in nickel-based superalloys form during heat treatment on a time scale inaccessible to direct molecular dynamics simulation, but can be studied using kinetic Monte Carlo (KMC) modelling. This requires reliable values for the barrier energies separating distinct configurations over the trajectory of the system. In this study, we validate vacancy migration barriers found with the Activation-Relaxation Technique nouveau (ARTn) method in partially ordered Ni75Al25 with a monovacancy using published potentials for the atomic interactions against first-principles methods. In a first step, we confirm that the ARTn barrier energies agree with those determined with the nudged elastic band (NEB) method. As the number of atoms used in those calculations is too great for direct ab initio calculations, we cut the cell size to 255 atoms, thus controlling finite size effects. We then use the plane-wave density functional theory code CASTEP and its inbuilt NEB method in the smaller cells. This provides us with a continuous validation chain from first principles to KMC simulations with interatomic potentials (IPs). We evaluate the barrier energies of five further IPs with NEB, demonstrating that none yields values with sufficient reliability for KMC simulations, with some of them failing completely. This is a first step towards quantifying the errors incurred in KMC simulations of precipitate formation and evolution.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"9 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141785094","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":"11 1","pages":""},"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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：