Pub Date : 2024-03-05DOI: 10.1088/1361-651x/ad2ba1
Eric Abercrombie, J Gregory McDaniel, Timothy Walsh
Despite the existence of time domain finite element formulations for viscoelastic materials, there are still substantial ways to improve the analysis. To the authors’ knowledge, the formulation of the problem is always done with respect to a single constitutive relation and so limits the implementer to a single scheme with which to model relaxation. Furthermore, all current constitutive relations involve the finding of fitting parameters for an analytical function, which is a sufficiently painful process to warrant the study of best fitting procedures to this day. In contrast, this effort is the first full derivation of the two dimensional problem from fundamental principles. It is also the first generalization of the problem, which frees users to select constitutive relations without re-derivation or re-expression of the problem. This approach is also the first approach to the problem that could lead to the elimination of constitutive relations for representing relaxation in viscoelastic materials. Following, the full derivation, several common constitutive relations are outlined with analysis of how they may best be implemented in the generalized form. Several expressions for viscoelastic terms are also provided given linear, quadratic, and exponential interpolation assumptions.
{"title":"A generalized time-domain constitutive finite element approach for viscoelastic materials","authors":"Eric Abercrombie, J Gregory McDaniel, Timothy Walsh","doi":"10.1088/1361-651x/ad2ba1","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2ba1","url":null,"abstract":"Despite the existence of time domain finite element formulations for viscoelastic materials, there are still substantial ways to improve the analysis. To the authors’ knowledge, the formulation of the problem is always done with respect to a single constitutive relation and so limits the implementer to a single scheme with which to model relaxation. Furthermore, all current constitutive relations involve the finding of fitting parameters for an analytical function, which is a sufficiently painful process to warrant the study of best fitting procedures to this day. In contrast, this effort is the first full derivation of the two dimensional problem from fundamental principles. It is also the first generalization of the problem, which frees users to select constitutive relations without re-derivation or re-expression of the problem. This approach is also the first approach to the problem that could lead to the elimination of constitutive relations for representing relaxation in viscoelastic materials. Following, the full derivation, several common constitutive relations are outlined with analysis of how they may best be implemented in the generalized form. Several expressions for viscoelastic terms are also provided given linear, quadratic, and exponential interpolation assumptions.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"3 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314227","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 : 2024-03-01DOI: 10.1088/1361-651x/ad29af
Aningi Mokhalingam, Indranil S Dalal, Shakti S Gupta
This work investigates the mechanical response of single-walled carbon nanotubes (SWCNTs) coupled through van der Waals and electrostatic forces using molecular dynamic (MD) simulations and a continuum model. In MD simulations, the covalent bond interactions between the carbon atoms are modeled using three sets of ReaxFF potential parameters (Strachan <italic toggle="yes">et al</italic> 2003 <italic toggle="yes">Phys. Rev. Lett.</italic> <bold>91</bold> 098301; Srinivasan <italic toggle="yes">et al</italic> 2015 <italic toggle="yes">J. Phys. Chem.</italic> A <bold>119</bold> 571–80; Damirchi <italic toggle="yes">et al</italic> 2020 <italic toggle="yes">J. Phys. Chem.</italic> C <bold>124</bold> 20488–97). The dynamic charges, dependent on the local environment, are calculated employing the charge equilibrium formalism within the ReaxFF. In the continuum model, the SWCNTs are modeled using the geometrically nonlinear Euler-Bernoulli beam theory. The Galerkin’s approach is used to discretize the equations of motion. An approximate model to account for the end charge concentration in the SWCNTs, calibrated from the MD data, is incorporated into the beam model. The pair of SWCNTs are prescribed with two sets of boundary conditions: Fixed–fixed and fixed–free. The pull-in voltages at which the two SWCNTs snap onto each other with fixed–fixed boundary conditions obtained from the MD simulations using the potential parameters of Strachan <italic toggle="yes">et al</italic> (2003 <italic toggle="yes">Phys. Rev. Lett.</italic> <bold>91</bold> 098301), Srinivasan <italic toggle="yes">et al</italic> (2015 <italic toggle="yes">J. Phys. Chem.</italic> A <bold>119</bold> 571–80) and Damirchi <italic toggle="yes">et al</italic> (2020 <italic toggle="yes">J. Phys. Chem.</italic> C <bold>124</bold> 20488–97) agree within an error of <inline-formula> <tex-math><?CDATA ${sim}0.5%$?></tex-math> <mml:math overflow="scroll"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mn>0.5</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> <inline-graphic xlink:href="msmsad29afieqn1.gif" xlink:type="simple"></inline-graphic> </inline-formula>, <inline-formula> <tex-math><?CDATA ${sim}0.5%$?></tex-math> <mml:math overflow="scroll"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mn>0.5</mml:mn><mml:mi mathvariant="normal">%</mml:mi></mml:math> <inline-graphic xlink:href="msmsad29afieqn2.gif" xlink:type="simple"></inline-graphic> </inline-formula>, and 7.2%, respectively, with those computed from the nonlinear beam theory. For fixed–free boundary conditions, the role of geometric nonlinearity is found to be insignificant. However, for this case, the concentrated charges play a significant role in determining the pull-in voltages. The post-pull-in response of the SWCNTs for both boundary conditions is investigated in detail through the MD simulations. The post-pull-in results presented here can be used as a benchmark for results obtained from continuum models in the future. Further,
{"title":"Mechanical response of van der Waals and charge coupled carbon nanotubes","authors":"Aningi Mokhalingam, Indranil S Dalal, Shakti S Gupta","doi":"10.1088/1361-651x/ad29af","DOIUrl":"https://doi.org/10.1088/1361-651x/ad29af","url":null,"abstract":"This work investigates the mechanical response of single-walled carbon nanotubes (SWCNTs) coupled through van der Waals and electrostatic forces using molecular dynamic (MD) simulations and a continuum model. In MD simulations, the covalent bond interactions between the carbon atoms are modeled using three sets of ReaxFF potential parameters (Strachan <italic toggle=\"yes\">et al</italic> 2003 <italic toggle=\"yes\">Phys. Rev. Lett.</italic>\u0000<bold>91</bold> 098301; Srinivasan <italic toggle=\"yes\">et al</italic> 2015 <italic toggle=\"yes\">J. Phys. Chem.</italic> A <bold>119</bold> 571–80; Damirchi <italic toggle=\"yes\">et al</italic> 2020 <italic toggle=\"yes\">J. Phys. Chem.</italic> C <bold>124</bold> 20488–97). The dynamic charges, dependent on the local environment, are calculated employing the charge equilibrium formalism within the ReaxFF. In the continuum model, the SWCNTs are modeled using the geometrically nonlinear Euler-Bernoulli beam theory. The Galerkin’s approach is used to discretize the equations of motion. An approximate model to account for the end charge concentration in the SWCNTs, calibrated from the MD data, is incorporated into the beam model. The pair of SWCNTs are prescribed with two sets of boundary conditions: Fixed–fixed and fixed–free. The pull-in voltages at which the two SWCNTs snap onto each other with fixed–fixed boundary conditions obtained from the MD simulations using the potential parameters of Strachan <italic toggle=\"yes\">et al</italic> (2003 <italic toggle=\"yes\">Phys. Rev. Lett.</italic>\u0000<bold>91</bold> 098301), Srinivasan <italic toggle=\"yes\">et al</italic> (2015 <italic toggle=\"yes\">J. Phys. Chem.</italic> A <bold>119</bold> 571–80) and Damirchi <italic toggle=\"yes\">et al</italic> (2020 <italic toggle=\"yes\">J. Phys. Chem.</italic> C <bold>124</bold> 20488–97) agree within an error of <inline-formula>\u0000<tex-math><?CDATA ${sim}0.5%$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mn>0.5</mml:mn><mml:mi mathvariant=\"normal\">%</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"msmsad29afieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, <inline-formula>\u0000<tex-math><?CDATA ${sim}0.5%$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mn>0.5</mml:mn><mml:mi mathvariant=\"normal\">%</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"msmsad29afieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, and 7.2%, respectively, with those computed from the nonlinear beam theory. For fixed–free boundary conditions, the role of geometric nonlinearity is found to be insignificant. However, for this case, the concentrated charges play a significant role in determining the pull-in voltages. The post-pull-in response of the SWCNTs for both boundary conditions is investigated in detail through the MD simulations. The post-pull-in results presented here can be used as a benchmark for results obtained from continuum models in the future. Further, ","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"37 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313961","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 : 2024-03-01DOI: 10.1088/1361-651x/ad2af5
Yu-Sheng Lu, Thi-Xuyen Bui, Te-Hua Fang
CoCrFeMnNi high-entropy alloy (HEA) has a high degree of thermodynamic stability and excellent ductility, making it a crucial structural material. However, the plastic deformation and microstructural behavior of gradient grain structured CoCrFeMnNi HEA under cutting remain unclear. In this study, the machining properties of gradient nanostructured CoCrFeMnNi HEA under conventional cutting were investigated by molecular dynamics simulation. The results displayed that the small grain gradient samples exhibited grain size softening. The shear angle and cutting ratio increased with the increase in the grain gradient. The grain boundaries of the low grain gradient samples were damaged and slid during the cutting process. Moreover, the dislocation density increased with the increasing grain gradient. The multi-dislocation nodes and the Lomer–Cottrell junction were produced in the grain coarsening gradient samples, contributing to work hardening. The cutting forces from low to high cutting velocities were 136.70, 147.91, 165.82, and 164.79 nN, which confirmed that the cutting forces increased with increased cutting velocity. This work elucidated the cutting mechanism of the nanostructured CoCrFeMnNi HEA and highlighted the influence of the gradient grain sizes.
钴铬铁镍高熵合金（HEA）具有高度的热力学稳定性和优异的延展性，是一种重要的结构材料。然而，梯度晶粒结构钴铬锰镍高熵合金在切削加工中的塑性变形和微观结构行为仍不清楚。本研究通过分子动力学模拟研究了梯度纳米结构 CoCrFeMnNi HEA 在常规切削条件下的加工性能。结果表明，小晶粒梯度样品表现出晶粒软化。剪切角和切削率随着晶粒梯度的增加而增大。低晶粒梯度样品的晶界在切削过程中受损并滑动。此外，位错密度随着晶粒梯度的增加而增加。晶粒粗化梯度样品中产生了多位错节点和 Lomer-Cottrell 交界，导致加工硬化。从低到高切削速度的切削力分别为 136.70、147.91、165.82 和 164.79 nN，这证实了切削力随切削速度的增加而增加。这项研究阐明了纳米结构 CoCrFeMnNi HEA 的切削机理，并强调了梯度晶粒尺寸的影响。
{"title":"Effects of grain boundary and gradient structure on machining property of CoCrFeMnNi alloys","authors":"Yu-Sheng Lu, Thi-Xuyen Bui, Te-Hua Fang","doi":"10.1088/1361-651x/ad2af5","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2af5","url":null,"abstract":"CoCrFeMnNi high-entropy alloy (HEA) has a high degree of thermodynamic stability and excellent ductility, making it a crucial structural material. However, the plastic deformation and microstructural behavior of gradient grain structured CoCrFeMnNi HEA under cutting remain unclear. In this study, the machining properties of gradient nanostructured CoCrFeMnNi HEA under conventional cutting were investigated by molecular dynamics simulation. The results displayed that the small grain gradient samples exhibited grain size softening. The shear angle and cutting ratio increased with the increase in the grain gradient. The grain boundaries of the low grain gradient samples were damaged and slid during the cutting process. Moreover, the dislocation density increased with the increasing grain gradient. The multi-dislocation nodes and the Lomer–Cottrell junction were produced in the grain coarsening gradient samples, contributing to work hardening. The cutting forces from low to high cutting velocities were 136.70, 147.91, 165.82, and 164.79 nN, which confirmed that the cutting forces increased with increased cutting velocity. This work elucidated the cutting mechanism of the nanostructured CoCrFeMnNi HEA and highlighted the influence of the gradient grain sizes.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"33 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314161","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 : 2024-02-29DOI: 10.1088/1361-651x/ad2af4
D Zöllner
The polycrystalline grain microstructure of metallic thin films coarsens during grain growth in a unique way when the initial grain structure contains multiple grains in the film thickness. A regime with fast coarsening is followed by a regime of slow coarsening. At the same time, the grain structure itself undergoes clear structural changes from a bulk-like to a bamboo-like structure. The overall coarsening process evolves continuously, whereas the growth paths of individual grains do not follow the ones observed and predicted in either two- or three-dimensional grain growth.
{"title":"Growth paths in polycrystalline thin films","authors":"D Zöllner","doi":"10.1088/1361-651x/ad2af4","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2af4","url":null,"abstract":"The polycrystalline grain microstructure of metallic thin films coarsens during grain growth in a unique way when the initial grain structure contains multiple grains in the film thickness. A regime with fast coarsening is followed by a regime of slow coarsening. At the same time, the grain structure itself undergoes clear structural changes from a bulk-like to a bamboo-like structure. The overall coarsening process evolves continuously, whereas the growth paths of individual grains do not follow the ones observed and predicted in either two- or three-dimensional grain growth.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"44 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313968","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 : 2024-02-28DOI: 10.1088/1361-651x/ad2787
Jaekwang Kim, Nikhil Chandra Admal
This paper investigates the statistics of two-dimensional grain microstructures during grain growth under anisotropic grain boundary (GB) energies and mobilities. We employ the threshold dynamics method, which allows for unparalleled computational speed, to simulate the full-field curvature motion of grain boundaries in a large polycrystal ensemble. Two sets of numerical experiments are performed to explore the effect of GB anisotropy on the evolution of microstructure features. In the first experiment, we focus on abnormal grain growth and find that GB anisotropy introduces a statistical preference for certain grain orientations. This leads to changes in the overall grain size distribution from the isotropic case. In the second experiment, we examine the development of texture and the growth of twin boundaries for different initial microstructures. We find that texture development and twin growth are more pronounced when the initial microstructure has a dominant fraction of high-angle grain boundaries. Our results suggest effective GB engineering strategies for improving material properties.
{"title":"Statistics of grain microstructure evolution under anisotropic grain boundary energies and mobilities using threshold-dynamics","authors":"Jaekwang Kim, Nikhil Chandra Admal","doi":"10.1088/1361-651x/ad2787","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2787","url":null,"abstract":"This paper investigates the statistics of two-dimensional grain microstructures during grain growth under anisotropic grain boundary (GB) energies and mobilities. We employ the threshold dynamics method, which allows for unparalleled computational speed, to simulate the full-field curvature motion of grain boundaries in a large polycrystal ensemble. Two sets of numerical experiments are performed to explore the effect of GB anisotropy on the evolution of microstructure features. In the first experiment, we focus on abnormal grain growth and find that GB anisotropy introduces a statistical preference for certain grain orientations. This leads to changes in the overall grain size distribution from the isotropic case. In the second experiment, we examine the development of texture and the growth of twin boundaries for different initial microstructures. We find that texture development and twin growth are more pronounced when the initial microstructure has a dominant fraction of high-angle grain boundaries. Our results suggest effective GB engineering strategies for improving material properties.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"135 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140009112","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 : 2024-02-26DOI: 10.1088/1361-651x/ad26a0
Jinxin Yu, Alfonso H W Ngan, David J Srolovitz, Jian Han
The interactions between dislocations and interface/grain boundaries, including dislocation absorption, transmission, and reflection, have garnered significant attention from the research community for their impact on the mechanical properties of materials. However, the traditional approaches used to simulate grain boundaries lack physical fidelity and are often incompatible across different simulation methods. We review a new mesoscale interface boundary condition based on Burgers vector conservation and kinetic dislocation reaction processes. The main focus of the paper is to demonstrate how to unify this boundary condition with different plasticity simulation approaches such as the crystal plasticity finite element (CPFEM), continuum dislocation dynamics (CDD), and discrete dislocation dynamics (DDD) methods. In DDD and CDD, plasticity is simulated based on dislocation activity; in the former, dislocations are described as discrete lines while in the latter in terms of dislocation density. CPFEM simulates plasticity in terms of slip on each slip system, without explicit treatment of dislocations; it is suitable for larger scale simulations. To validate our interface boundary condition, we implemented simulations using both the CPFEM method and a two-dimensional CDD model. Our results show that our compact and physically realistic interface boundary condition can be easily integrated into multiscale simulation methods and yield novel results consistent with experimental observations.
{"title":"Application of rigorous interface boundary conditions in mesoscale plasticity simulations","authors":"Jinxin Yu, Alfonso H W Ngan, David J Srolovitz, Jian Han","doi":"10.1088/1361-651x/ad26a0","DOIUrl":"https://doi.org/10.1088/1361-651x/ad26a0","url":null,"abstract":"The interactions between dislocations and interface/grain boundaries, including dislocation absorption, transmission, and reflection, have garnered significant attention from the research community for their impact on the mechanical properties of materials. However, the traditional approaches used to simulate grain boundaries lack physical fidelity and are often incompatible across different simulation methods. We review a new mesoscale interface boundary condition based on Burgers vector conservation and kinetic dislocation reaction processes. The main focus of the paper is to demonstrate how to unify this boundary condition with different plasticity simulation approaches such as the crystal plasticity finite element (CPFEM), continuum dislocation dynamics (CDD), and discrete dislocation dynamics (DDD) methods. In DDD and CDD, plasticity is simulated based on dislocation activity; in the former, dislocations are described as discrete lines while in the latter in terms of dislocation density. CPFEM simulates plasticity in terms of slip on each slip system, without explicit treatment of dislocations; it is suitable for larger scale simulations. To validate our interface boundary condition, we implemented simulations using both the CPFEM method and a two-dimensional CDD model. Our results show that our compact and physically realistic interface boundary condition can be easily integrated into multiscale simulation methods and yield novel results consistent with experimental observations.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"36 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140009225","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 : 2024-02-19DOI: 10.1088/1361-651x/ad2786
Veer Pal, 0009-0000-5435-5614Ajay1
Knowledge of the internal configuration of carbon atoms inside a moire unit cell of twisted bi-layer graphene (TBG) would enhance the accuracy of many-body quantum mechanical calculations related to TBG. This work put forward a comprehensive theoretical study of moire pattern in TBG, supported with computational analysis; which seek a mechanism to determine the internal configuration of carbon atoms inside a moire unit cell of TBG. This study first time establishes that all twist angles are commensurate twist angles which produce perfectly periodic commensurate moire patterns of TBG. It is also first time established that strain appearing in moire patterns of TBG can occur purely due to intrinsic reasons. Taking some insight from available experimental data related to TBG systems and conventional bi-layer graphene systems, a mathematical model is also presented for corrugation in TBG. Finally we present an universal algorithm to determine the internal configuration of carbon atoms inside a moire unit cell of TBG, which is first of its kind.
{"title":"Twist angle, strain, corrugation and moire unit cell in twisted bi-layer graphene","authors":"Veer Pal, 0009-0000-5435-5614Ajay1","doi":"10.1088/1361-651x/ad2786","DOIUrl":"https://doi.org/10.1088/1361-651x/ad2786","url":null,"abstract":"Knowledge of the internal configuration of carbon atoms inside a moire unit cell of twisted bi-layer graphene (TBG) would enhance the accuracy of many-body quantum mechanical calculations related to TBG. This work put forward a comprehensive theoretical study of moire pattern in TBG, supported with computational analysis; which seek a mechanism to determine the internal configuration of carbon atoms inside a moire unit cell of TBG. This study first time establishes that all twist angles are commensurate twist angles which produce perfectly periodic commensurate moire patterns of TBG. It is also first time established that strain appearing in moire patterns of TBG can occur purely due to intrinsic reasons. Taking some insight from available experimental data related to TBG systems and conventional bi-layer graphene systems, a mathematical model is also presented for corrugation in TBG. Finally we present an universal algorithm to determine the internal configuration of carbon atoms inside a moire unit cell of TBG, which is first of its kind.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"80 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140008740","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}
Molybdenum disulfide (MoS2) is an alternate absorber layer in 2D solar cells owing to its potential of proficient sunlight harvesting. The optimum electrical and optical properties of MoS2 validate it as a suitable photovoltaic absorber material. This work investigates the performance of 2D (and multi-layer) MoS2-based vertically stacked solar cell by numerical simulation process using one dimensional solar cell capacitance simulator (SCAPS). Two device configurations based on Schottky junction (ITO/n-MoS2/Au) and pn junction (ITO/n-MoS2/p-MoS2/Au) have been theoretically analyzed. The feasibility of ultra-thin transparent solar cells is also demonstrated, which is motivating from a technological outlook. Initially, the properties of the active layers are optimized to give the highest performance. The findings are explained on the basis of band alignment between the electrodes and the different layers. The potential barrier developed at the interface of different materials governs the output of the cells. The calculations forecast the material properties, which need to be tuned to fabricate solar cells with enhanced efficiency. After optimization, the highest efficiency obtained for single n-MoS2-based solar cell is 10.22%, while for the pn junction solar cell it is 16.86%. The optimized cells exhibit high open circuit voltages of ∼1.2 V, which is an essential factor for commercial realization of solar cells. Lastly, the performance of transparent solar cells based on thin 2D MoS2 films has been predicted which showcases the efficiency in the range of 0.78%–4.36%. These homo-junction device investigations of solely MoS2 layer along with employment of a strict control on the defects during deposition and fabrication of MoS2-based solar cells can ensure better performance of the device. Thus, it can open ways to develop next generation feasible solar cells with higher power density as compared to existing technology.
{"title":"Performance evaluation of 2D MoS2-based solar cells and realization of transparent ultra-thin devices","authors":"Shweta1, Vinamrita Singh, Kaushal Kumar, Arun Kumar","doi":"10.1088/1361-651x/ad237d","DOIUrl":"https://doi.org/10.1088/1361-651x/ad237d","url":null,"abstract":"Molybdenum disulfide (MoS<sub>2</sub>) is an alternate absorber layer in 2D solar cells owing to its potential of proficient sunlight harvesting. The optimum electrical and optical properties of MoS<sub>2</sub> validate it as a suitable photovoltaic absorber material. This work investigates the performance of 2D (and multi-layer) MoS<sub>2</sub>-based vertically stacked solar cell by numerical simulation process using one dimensional solar cell capacitance simulator (SCAPS). Two device configurations based on Schottky junction (ITO/<italic toggle=\"yes\">n</italic>-MoS<sub>2</sub>/Au) and <italic toggle=\"yes\">pn</italic> junction (ITO/<italic toggle=\"yes\">n</italic>-MoS<sub>2</sub>/<italic toggle=\"yes\">p</italic>-MoS<sub>2</sub>/Au) have been theoretically analyzed. The feasibility of ultra-thin transparent solar cells is also demonstrated, which is motivating from a technological outlook. Initially, the properties of the active layers are optimized to give the highest performance. The findings are explained on the basis of band alignment between the electrodes and the different layers. The potential barrier developed at the interface of different materials governs the output of the cells. The calculations forecast the material properties, which need to be tuned to fabricate solar cells with enhanced efficiency. After optimization, the highest efficiency obtained for single <italic toggle=\"yes\">n</italic>-MoS<sub>2</sub>-based solar cell is 10.22%, while for the <italic toggle=\"yes\">pn</italic> junction solar cell it is 16.86%. The optimized cells exhibit high open circuit voltages of ∼1.2 V, which is an essential factor for commercial realization of solar cells. Lastly, the performance of transparent solar cells based on thin 2D MoS<sub>2</sub> films has been predicted which showcases the efficiency in the range of 0.78%–4.36%. These homo-junction device investigations of solely MoS<sub>2</sub> layer along with employment of a strict control on the defects during deposition and fabrication of MoS<sub>2</sub>-based solar cells can ensure better performance of the device. Thus, it can open ways to develop next generation feasible solar cells with higher power density as compared to existing technology.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"12 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139761305","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 : 2024-01-10DOI: 10.1088/1361-651x/ad1ce0
Fatima Zohra Behar, S. Meskine, Abdelkader Boukortt, Abdesamed Benbedra
In this study, we perform first-principles calculations using density functional theory to examine the structural, electronic, thermodynamic, and thermoelectric properties of the Mg2X (X = Si, Ge and Sn) compounds under uniaxial compression within the generalized gradient and modified Beck-Johnson approximations. It is found that the band gap of Mg2Si, Mg2Ge and Mg2Sn decreases with applied uniaxial pressure and changes its direction from Г-Х to Г-К. The results of phonon frequencies indicate that the studied compounds are dynamically stable at zero and higher uniaxial strains. Furthermore, the uniaxial compression and temperature dependence of the Gibbs free energy, heat capacity and thermal expansion coefficient are investigated in the frame of the quasi-harmonic approximation. The semiclassical-Boltzmann method is used to study the Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit ZT as a function of both temperature and uniaxial pressure. It is shown that the Seebeck coefficient decreases with increasing pressure whereas thermal conductivity increases, which leads to the lowering in the value of ZT and thus to a worse thermoelectric performance of the studied materials.
{"title":"Response of Mg2X (X = Si, Ge and Sn) compounds to extreme uniaxial compression: first-principles calculations","authors":"Fatima Zohra Behar, S. Meskine, Abdelkader Boukortt, Abdesamed Benbedra","doi":"10.1088/1361-651x/ad1ce0","DOIUrl":"https://doi.org/10.1088/1361-651x/ad1ce0","url":null,"abstract":"\u0000 In this study, we perform first-principles calculations using density functional theory to examine the structural, electronic, thermodynamic, and thermoelectric properties of the Mg2X (X = Si, Ge and Sn) compounds under uniaxial compression within the generalized gradient and modified Beck-Johnson approximations. It is found that the band gap of Mg2Si, Mg2Ge and Mg2Sn decreases with applied uniaxial pressure and changes its direction from Г-Х to Г-К. The results of phonon frequencies indicate that the studied compounds are dynamically stable at zero and higher uniaxial strains. Furthermore, the uniaxial compression and temperature dependence of the Gibbs free energy, heat capacity and thermal expansion coefficient are investigated in the frame of the quasi-harmonic approximation. The semiclassical-Boltzmann method is used to study the Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit ZT as a function of both temperature and uniaxial pressure. It is shown that the Seebeck coefficient decreases with increasing pressure whereas thermal conductivity increases, which leads to the lowering in the value of ZT and thus to a worse thermoelectric performance of the studied materials.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"5 3","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139440026","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 : 2024-01-09DOI: 10.1088/1361-651x/ad1cd0
Yu Jia, Huadian Zhang, Manoj K. Shukla, Steven Larson, S. Nouranian, A. M. Rajendran, Shan Jiang
This study employs a series of molecular dynamics (MD) simulations, utilizing three commonly used interatomic potentials, i.e., van Beest, Kramer, and van Santen (BKS), Vashishta, and Tersoff to analyze the structural and mechanical characteristics within both void-free and single-void αquartz configurations. Two distinct ensembles, NVT and NPT, were separately applied to investigate the tensile response. The validation of MD results included a comparative study of the three potentials as well as a comparison with experimental microstructural and tension studies. While BKS and Vashishta potentials accurately calculated the bond lengths, density and lattice parameters compared to the experimental values for void-free α-quartz, the results obtained with Tersoff potential exhibited relatively large deviations. The BKS potential offered an accurate description of the mechanical response of α-quartz by successfully predicting stress-strain curves. The Vashishta potential overpredicted Young’s modulus as compared to BKS. The Tersoff potential could capture the elastic deformation but was unable to predict the fracture behavior. The presence of a spherical void significantly reduced mechanical behavior of α-quartz, and the extent of this reduction was highly related to void size. When applying the BKS potential with an NVT ensemble, the ultimate tensile strengths decreased by 19% and 72% with void sizes of 2.5 and 15 Å, respectively. Equivalent stress analysis reveals that the BKS potential can effectively capture greater stress concentration around the void compared to other two potentials. Based on the comparison study, the BKS potential seems to be the most suitable one to describe α-quartz under tension in a realistic manner.
{"title":"Mechanical behavior of alpha quartz with void defects under tension: A molecular dynamics study using different interatomic potentials","authors":"Yu Jia, Huadian Zhang, Manoj K. Shukla, Steven Larson, S. Nouranian, A. M. Rajendran, Shan Jiang","doi":"10.1088/1361-651x/ad1cd0","DOIUrl":"https://doi.org/10.1088/1361-651x/ad1cd0","url":null,"abstract":"\u0000 This study employs a series of molecular dynamics (MD) simulations, utilizing three commonly used interatomic potentials, i.e., van Beest, Kramer, and van Santen (BKS), Vashishta, and Tersoff to analyze the structural and mechanical characteristics within both void-free and single-void αquartz configurations. Two distinct ensembles, NVT and NPT, were separately applied to investigate the tensile response. The validation of MD results included a comparative study of the three potentials as well as a comparison with experimental microstructural and tension studies. While BKS and Vashishta potentials accurately calculated the bond lengths, density and lattice parameters compared to the experimental values for void-free α-quartz, the results obtained with Tersoff potential exhibited relatively large deviations. The BKS potential offered an accurate description of the mechanical response of α-quartz by successfully predicting stress-strain curves. The Vashishta potential overpredicted Young’s modulus as compared to BKS. The Tersoff potential could capture the elastic deformation but was unable to predict the fracture behavior. The presence of a spherical void significantly reduced mechanical behavior of α-quartz, and the extent of this reduction was highly related to void size. When applying the BKS potential with an NVT ensemble, the ultimate tensile strengths decreased by 19% and 72% with void sizes of 2.5 and 15 Å, respectively. Equivalent stress analysis reveals that the BKS potential can effectively capture greater stress concentration around the void compared to other two potentials. Based on the comparison study, the BKS potential seems to be the most suitable one to describe α-quartz under tension in a realistic manner.","PeriodicalId":18648,"journal":{"name":"Modelling and Simulation in Materials Science and Engineering","volume":"104 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139444733","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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