Anti-icing is crucial for numerous instruments and devices in low temperature circum- stance. One of the approaches in anti-icing is to reduce ice adhesion strength, seeking spontaneous de-icing processes by natural f...Anti-icing is crucial for numerous instruments and devices in low temperature circum- stance. One of the approaches in anti-icing is to reduce ice adhesion strength, seeking spontaneous de-icing processes by natural forces of gravity or by winds. In order to enable tai- lored surface icephobicity design, research requires a good theoretical understanding of the atomistic interacting mechanisms between water/ice molecules and their adhering substrates. Herein, this work focuses on using atomistic modeling and molecular dynamics simulation to build a nanosized ice-cube adhering onto silicon surface, with different contact modes of solid-solid and solid-liquid-solid patterns. This study provides atomistic models for probing nanoscale ice adhesion mechanics and theoretical platforms for explaining experimental results.展开更多
During the past decade,significant progress has been achieved in the application of material modeling to aid technology development in semiconductor manufacturing companies such as Intel.In this paper,we review exampl...During the past decade,significant progress has been achieved in the application of material modeling to aid technology development in semiconductor manufacturing companies such as Intel.In this paper,we review examples of applications involving a complex set of material modeling tools and methodologies and share our perspective of the future of the area.Examples are given illustrating the landscape of useful physical models and approaches along with commentary addressing tool relevance and simulation efficiency issues.While the scope of this paper precludes providing in-depth details,references to more focused publications are shared.Finally,we outline how to approach constructing a general infrastructure for supporting TCAD material modeling applications.展开更多
Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employ...Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self- consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The ei^ect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.展开更多
As a typical configuration in plastic deformations, dislocation arrays possess a large variation of the separation of the partial dislocation pairs in face-centered cubic（fcc） metals. This can be manifested convenie...As a typical configuration in plastic deformations, dislocation arrays possess a large variation of the separation of the partial dislocation pairs in face-centered cubic（fcc） metals. This can be manifested conveniently by an effective stacking fault energy（SFE）. The effective SFE of dislocation arrays is described within the elastic theory of dislocations and verified by atomistic simulations. The atomistic modeling results reveal that the general formulae of the effective SFE can give a reasonably satisfactory prediction for all dislocation types, especially for edge dislocation arrays. Furthermore, the predicted variation of the effective SFE is consistent with several previous experiments, in which the measured SFE is not definite, changing with dislocation density. Our approach could provide better understandings of cross-slip and the competition between slip and twinning during plastic deformations in fcc metals.展开更多
In nuclear structural materials, the nuclear irradiations induce the precipitations of soluble elements or produce the insoluble elements such as He atoms that may form clusters, heavily shortening the service life-ti...In nuclear structural materials, the nuclear irradiations induce the precipitations of soluble elements or produce the insoluble elements such as He atoms that may form clusters, heavily shortening the service life-times of the materials. In the present work, a diffusion model is developed to predict where and how fast the solute atoms （either soluble or insoluble） aggregate, and this model is applied to the study of the formation and growth of He bubbles in metal tritides （PdT0.6, ErT2, NbT0.0225, VT0.5, TaT0.097, TiT1.5, ZrT1.6） within one thousand days. The results are in good agreement with the available experimental observations and suggest that searching for metals with a barrier of more than 1.1 eV for a single He atom diffusion and making more defects in metal tritides can significantly reduce the growth of He bubbles and extend the service time of the metals.展开更多
The surface oxidation patterns of iron or low-carbon steels are critical to their life when serving in typical damp environments. An accurate determination of the oxidation pattern entails tracking the iron atoms oxid...The surface oxidation patterns of iron or low-carbon steels are critical to their life when serving in typical damp environments. An accurate determination of the oxidation pattern entails tracking the iron atoms oxidized at the iron/steel-moisture interface. Using a quantum chemistry-based force field that is capable of simulating chemical reactions, this paper studies the process of iron oxidation under a typical moist condition. The oxidation of iron surface was found to be highly thermodynamic and dependent on the availability of reactants. A triplex structure was formed at the end of a three-stage oxidation process to reduce the overall oxidation speed. The results from this study shed light on the atomistic mechanism of iron oxidation; therefore can be used to guide the protection of general ferrous-based iron/steel structures.展开更多
When wood-based activated carbon was tailored with quaternary ammonium/epoxide(QAE) forming compounds(QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid(PF...When wood-based activated carbon was tailored with quaternary ammonium/epoxide(QAE) forming compounds(QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid(PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before halfbreakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.展开更多
Interstitial alloying has emerged as a powerful strategy to tune microstructure and microproperties of high-entropy alloys(HEAs) due to the strong interaction of interstitials with constituent elements and crystal def...Interstitial alloying has emerged as a powerful strategy to tune microstructure and microproperties of high-entropy alloys(HEAs) due to the strong interaction of interstitials with constituent elements and crystal defects,which enables the development of advanced alloys with superior mechanical and functional properties. The paper reviews the latest progress in the atomic-scale understanding of the effects of various interstitials, including carbon, boron, nitrogen, oxygen, and hydrogen, on the microstructure, stability, mechanical properties, and deformation behavior of HEAs. Emphases are placed on the in-depth insights on the interaction of interstitials with constituent elements and crystal defects, such as vacancies,stacking faults, and grain boundaries. Key parameters for rapid prediction of intrinsic properties of HEAs are also discussed. Finally, we highlight some unsolved issues and provide perspectives for future research directions.展开更多
In this paper,we develop the residual based a posteriori error estimates and the corresponding adaptive mesh refinement algorithm for atomistic/continuum(a/c)coupling with finite range interactions in two dimensions.W...In this paper,we develop the residual based a posteriori error estimates and the corresponding adaptive mesh refinement algorithm for atomistic/continuum(a/c)coupling with finite range interactions in two dimensions.We have systematically derived a new explicitly computable stress tensor formula for finite range in-teractions.In particular,we use the geometric reconstruction based consistent atomistic/continuum(GRAC)coupling scheme,which is quasi-optimal if the continuum model is discretized by P1 finite elements.The numerical results of the adaptive mesh refinement algorithm is consistent with the quasi-optimal a priori error estimates.展开更多
In this paper,an atom-continuum coupled model for thermo-mechanical behaviors in micro-nano scales is presented.A representative volume element consisting of atom clusters is used to represent the microstructure of ma...In this paper,an atom-continuum coupled model for thermo-mechanical behaviors in micro-nano scales is presented.A representative volume element consisting of atom clusters is used to represent the microstructure of materials.The atom motions in the RVE are divided into two phases,structural deformations and thermal vibrations.For the structural deformations,nonlinear and nonlocal deformation at atomic scales is considered.The atomistic-continuum equations are constructed based on momentum and energy conservation law.The non-locality and nonlinearity of atomistic interactions are built into the thermo-mechanical constitutive equations.The coupled atomistic-continuum thermal-mechanical simulation process is also suggested in this work.展开更多
In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a s...In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a system of coupled eigenvalue PDEs that is usually supplemented by interface boundary conditions that can be derived from a variational formulation of the problem.We analyze such a system for the envelope functions and show that a failure to restrict their Fourier expansion coeffi-cients to small k components would lead to the appearance of non-physical solutions.We survey the existing methodologies to eliminate this difficulty and propose a simple and effective solution.This solution is demonstrated on an example of a two-band model for both bulk materials and low-dimensional nanostructures.Finally,based on the above requirement of small k,we derive a model for nanostructures with cylindrical symmetry and apply the developed model to the analysis of quantum dots using an eight-band model.展开更多
基金the financial support from Statoil ASA (Norway) through the project of nanotechnology for anti-icing application, NTNU stjerneprogramthe Research Council of Norway through the FRINATEK project Towards Design of Super-Low Ice Adhesion Surfaces ( SLICE,250990 )
文摘Anti-icing is crucial for numerous instruments and devices in low temperature circum- stance. One of the approaches in anti-icing is to reduce ice adhesion strength, seeking spontaneous de-icing processes by natural forces of gravity or by winds. In order to enable tai- lored surface icephobicity design, research requires a good theoretical understanding of the atomistic interacting mechanisms between water/ice molecules and their adhering substrates. Herein, this work focuses on using atomistic modeling and molecular dynamics simulation to build a nanosized ice-cube adhering onto silicon surface, with different contact modes of solid-solid and solid-liquid-solid patterns. This study provides atomistic models for probing nanoscale ice adhesion mechanics and theoretical platforms for explaining experimental results.
文摘During the past decade,significant progress has been achieved in the application of material modeling to aid technology development in semiconductor manufacturing companies such as Intel.In this paper,we review examples of applications involving a complex set of material modeling tools and methodologies and share our perspective of the future of the area.Examples are given illustrating the landscape of useful physical models and approaches along with commentary addressing tool relevance and simulation efficiency issues.While the scope of this paper precludes providing in-depth details,references to more focused publications are shared.Finally,we outline how to approach constructing a general infrastructure for supporting TCAD material modeling applications.
基金supported by the National Natural Science Foundation of China (Grant No. 10476019)the Fundamental Research Funds for the Central Universities of China (Grant No. JY10000904018)
文摘Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self- consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The ei^ect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.
基金support of this work by the Program of ‘‘One Hundred Talented People’’ of the Chinese Academy of Sciences (JBY) and the National Natural Science Foundation of China (Nos. 51571198, 51771206, 51331007, 51501197 and 51401207)
文摘As a typical configuration in plastic deformations, dislocation arrays possess a large variation of the separation of the partial dislocation pairs in face-centered cubic（fcc） metals. This can be manifested conveniently by an effective stacking fault energy（SFE）. The effective SFE of dislocation arrays is described within the elastic theory of dislocations and verified by atomistic simulations. The atomistic modeling results reveal that the general formulae of the effective SFE can give a reasonably satisfactory prediction for all dislocation types, especially for edge dislocation arrays. Furthermore, the predicted variation of the effective SFE is consistent with several previous experiments, in which the measured SFE is not definite, changing with dislocation density. Our approach could provide better understandings of cross-slip and the competition between slip and twinning during plastic deformations in fcc metals.
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130071110018)the National Natural Science Foundation of China(Grant No.11274073)
文摘In nuclear structural materials, the nuclear irradiations induce the precipitations of soluble elements or produce the insoluble elements such as He atoms that may form clusters, heavily shortening the service life-times of the materials. In the present work, a diffusion model is developed to predict where and how fast the solute atoms （either soluble or insoluble） aggregate, and this model is applied to the study of the formation and growth of He bubbles in metal tritides （PdT0.6, ErT2, NbT0.0225, VT0.5, TaT0.097, TiT1.5, ZrT1.6） within one thousand days. The results are in good agreement with the available experimental observations and suggest that searching for metals with a barrier of more than 1.1 eV for a single He atom diffusion and making more defects in metal tritides can significantly reduce the growth of He bubbles and extend the service time of the metals.
文摘The surface oxidation patterns of iron or low-carbon steels are critical to their life when serving in typical damp environments. An accurate determination of the oxidation pattern entails tracking the iron atoms oxidized at the iron/steel-moisture interface. Using a quantum chemistry-based force field that is capable of simulating chemical reactions, this paper studies the process of iron oxidation under a typical moist condition. The oxidation of iron surface was found to be highly thermodynamic and dependent on the availability of reactants. A triplex structure was formed at the end of a three-stage oxidation process to reduce the overall oxidation speed. The results from this study shed light on the atomistic mechanism of iron oxidation; therefore can be used to guide the protection of general ferrous-based iron/steel structures.
基金funding from Evoqua Companythe National Natural Science Foundation of China (Nos. 51878090 and 51808066)the Chinese Scholarship Council for financial support。
文摘When wood-based activated carbon was tailored with quaternary ammonium/epoxide(QAE) forming compounds(QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid(PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before halfbreakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.
基金the financial support from National Natural Science Foundation of China(No.52171162)Research Grants Council of Hong Kong(Nos.15202824,15227121,C5002-24Y,C1017D21GF,and C1020D21GF)+4 种基金Shenzhen Science and Technology Program(No.JCYJ20210324142203009)the Research Institute for Advanced Manufacturing Fund(No.P0046108)PolyU Fund(Nos.P0044243 and P0043467)Guangdong Science and Technology Innovation Foundation(No.2023A1515240061)Open access funding provided by The Hong Kong Polytechnic University
文摘Interstitial alloying has emerged as a powerful strategy to tune microstructure and microproperties of high-entropy alloys(HEAs) due to the strong interaction of interstitials with constituent elements and crystal defects,which enables the development of advanced alloys with superior mechanical and functional properties. The paper reviews the latest progress in the atomic-scale understanding of the effects of various interstitials, including carbon, boron, nitrogen, oxygen, and hydrogen, on the microstructure, stability, mechanical properties, and deformation behavior of HEAs. Emphases are placed on the in-depth insights on the interaction of interstitials with constituent elements and crystal defects, such as vacancies,stacking faults, and grain boundaries. Key parameters for rapid prediction of intrinsic properties of HEAs are also discussed. Finally, we highlight some unsolved issues and provide perspectives for future research directions.
基金supported by National Natural Science Foundation of China grant 11861131004,11771040,91430106supported by Natural Science Foundation of China grant 11871339,11861131004,11571314,11471214 and the One Thousand Plan of China for young scientists.
文摘In this paper,we develop the residual based a posteriori error estimates and the corresponding adaptive mesh refinement algorithm for atomistic/continuum(a/c)coupling with finite range interactions in two dimensions.We have systematically derived a new explicitly computable stress tensor formula for finite range in-teractions.In particular,we use the geometric reconstruction based consistent atomistic/continuum(GRAC)coupling scheme,which is quasi-optimal if the continuum model is discretized by P1 finite elements.The numerical results of the adaptive mesh refinement algorithm is consistent with the quasi-optimal a priori error estimates.
基金supported by the Special Funds for the National Basic Research Program of China (973 Project) (Grant No. 2010CB832702)the National Natural Science Foundation of China (Grant No. 90916027)also supported by NSAF (Grant No.10976004)
文摘In this paper,an atom-continuum coupled model for thermo-mechanical behaviors in micro-nano scales is presented.A representative volume element consisting of atom clusters is used to represent the microstructure of materials.The atom motions in the RVE are divided into two phases,structural deformations and thermal vibrations.For the structural deformations,nonlinear and nonlocal deformation at atomic scales is considered.The atomistic-continuum equations are constructed based on momentum and energy conservation law.The non-locality and nonlinearity of atomistic interactions are built into the thermo-mechanical constitutive equations.The coupled atomistic-continuum thermal-mechanical simulation process is also suggested in this work.
文摘In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a system of coupled eigenvalue PDEs that is usually supplemented by interface boundary conditions that can be derived from a variational formulation of the problem.We analyze such a system for the envelope functions and show that a failure to restrict their Fourier expansion coeffi-cients to small k components would lead to the appearance of non-physical solutions.We survey the existing methodologies to eliminate this difficulty and propose a simple and effective solution.This solution is demonstrated on an example of a two-band model for both bulk materials and low-dimensional nanostructures.Finally,based on the above requirement of small k,we derive a model for nanostructures with cylindrical symmetry and apply the developed model to the analysis of quantum dots using an eight-band model.
