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Adhesive contact:from atomistic model to continuum model

Chinese Physics B 2011年第4期20卷 286-294页

作者：樊康旗贾建援朱应敏张秀艳 School of Electronical & Mechanical Engineering Xidian University

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.

关键词： Lennard-Jones potential adhesive contact atomistic model adhesion hysteresis

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Structure descriptor for surface passivation in the simulation of atomistic models

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Science China(Information Sciences) 2017年第3期60卷 68-77页

作者： Li CAO Siukong KOO Jian SUN Guanhua CHEN Wenping WANG Department of Computer Science The University of Hong Kong Department of Chemistry The University of Hong Kong

Surface passivation is an essential step for atomistic simulations. There can be many possible surface passivation results for a given device model, such as semiconductor devices that consist of Si, Ga As, or other materials because the bonding directions of the surface atoms may not be unique. Based on the structure analysis of the given model, a generation method with structure descriptor(SDG) is proposed for surface *** with other existing solutions, the SDG method not only provides trimmer results, but also reduces the torsion angle energy of the model, which is preferred in the simulation of atomistic models. The efficiency of this method was validated through test results from several applications.

关键词： computer aided design structure analysis torsion angle universal force field surface passivation atomistic model

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Adsorption mechanisms of PFOA onto activated carbon anchored with quaternary ammonium/epoxide-forming compounds: A combination of experiment and model studies

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Journal of Environmental Sciences 2020年第12期32卷 94-102页

作者： Chen Yuan Yang Huang Fred SCannon Zhiwei Zhao Shenzhen Academy of Environmental Science Shenzhen 518001China College of Urban Construction and Environmental Engineering Chongqing UniversityChongqing 400045China Department of Civil and Environmental Engineering Pennsylvania State UniversityUniversity ParkPA 16802USA College of Resources and Environment Chengdu University of Information TechnologyChengdu 610225China

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.

关键词： Perfluorooctanoic acid Nitrate Carbon atomistic model Adsorption mechanism

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Atom-continuum coupled model for thermo-mechanical behavior of materials in micro-nano scales

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Science China(Physics,Mechanics & Astronomy) 2012年第6期55卷 1125-1137页

作者： XIANG MeiZhen CUI JunZhi LI BoWen TIAN Xia Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China LSEC ICMSEC Academy of Mathematics and Systems Sciences Chinese Academy of Sciences Beijing 100190 China College of Mechanics and Materials Hohai University Nanjing 210098 China

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 *** atom motions in the RVE are divided into two phases,structural deformations and thermal *** the structural deformations,nonlinear and nonlocal deformation at atomic scales is *** atomistic-continuum equations are constructed based on momentum and energy conservation *** non-locality and nonlinearity of atomistic interactions are built into the thermo-mechanical constitutive *** coupled atomistic-continuum thermal-mechanical simulation process is also suggested in this work.

关键词： atom-continuum coupled (ACC) model atomistic model thermo-mechanical behaviors nonlocality multiscale model

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