钚因放射性衰变而出现自辐照老化效应。钚中氦行为是理解钚自辐照老化效应的一个基础和前提。运用分子动力学模拟技术,计算研究了钚中缺陷行为、氦与缺陷的相互作用、氦泡的初始形核过程、氦泡的长大过程以及氦泡对钚材料宏观性能的影...钚因放射性衰变而出现自辐照老化效应。钚中氦行为是理解钚自辐照老化效应的一个基础和前提。运用分子动力学模拟技术,计算研究了钚中缺陷行为、氦与缺陷的相互作用、氦泡的初始形核过程、氦泡的长大过程以及氦泡对钚材料宏观性能的影响等。其中,钚-钚、钚-氦和氦-氦相互作用势分别采用修正嵌入原子多体势(modified embedded atom method,MEAM)、Morse对势和Lennard-Jones对势。主要的计算结果表明,氦原子与空位的结合能较大,在钚的自辐照过程中,两者易于结合并形成氦-空位团簇,成为氦泡的前驱体;氦泡可通过冲出位错环的机制而长大;氦泡的压力在GPa量级,且氦泡引起的基体膨胀很小。展开更多
The plastic deformation processes of magnesium alloys near a void at atomic scale level were examined through molecular dynamics(MD)simulation.The modified embedded atom method(MEAM)potentials were employed to charact...The plastic deformation processes of magnesium alloys near a void at atomic scale level were examined through molecular dynamics(MD)simulation.The modified embedded atom method(MEAM)potentials were employed to characterize the interaction between atoms of the magnesium alloy specimen with only a void.The void growth and crystal failure processes for hexagonal close-packed(hcp)structure were observed.The calculating results reveal that the deformation mechanism near a void in magnesium alloy is a complex process.The passivation around the void,dislocation emission,and coalescence of the void and micro-cavities lead to rapid void growth.展开更多
Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problem...Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problems,but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys.Here,an intera-tomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed.The ternary potential can accurately predict the structure and thermodynamic properties of the Nb-Al-Ti system.The potential shows that the optimal Nb content for high-temperature strength-ductility synergy of TiAl single crystals is 8%,consistent with the amount of miracle synthesis of TiAl single crystals.Tensile simulations further show that the developed potential can make an effective prediction at high temperatures,indicating the potential for the development and applications of high-temperature Nb-Al-Ti ternary systems.展开更多
本文采用基于密度泛函理论发展的嵌入原子方法,推导了由半经验函数嵌入能和排斥势所表达的表面晶格动力学矩阵公式,以CU(100)面为例,得到了该面三个主要对称方向的色散关系.其中,沿 FX 方向的瑞利声子色散曲线与新近的电子能量损失谱所...本文采用基于密度泛函理论发展的嵌入原子方法,推导了由半经验函数嵌入能和排斥势所表达的表面晶格动力学矩阵公式,以CU(100)面为例,得到了该面三个主要对称方向的色散关系.其中,沿 FX 方向的瑞利声子色散曲线与新近的电子能量损失谱所得实验结果相比,符合较好.文中还讨论了一些表面模的局域程度以及振动方式.展开更多
Using embedded-atom-method potential for Pd and MORSE potential for the interaction between H and Pd atoms, the adsorption properties of H atoms on Pd (211), (311) and (511) stepped defective surfaces were calculated ...Using embedded-atom-method potential for Pd and MORSE potential for the interaction between H and Pd atoms, the adsorption properties of H atoms on Pd (211), (311) and (511) stepped defective surfaces were calculated systematically. For Pd (311) surface, it is found that the four-fold hollow sites H4 are the preferable sites for H atoms being adsorbed on these Pd defective surfaces. The sites H4 are the most stable adsorbed sites and the three-fold hollow sites Hf and Hh are metastable ones. The calculated results are in reasonable agreement with the HREELS experiment results. For the (211) and (511) stepped defective surfaces of Pd, our calculation shows that the most stable adsorption sites are H5 and H2 respectively, both of them are four fold hollow sites.展开更多
文摘钚因放射性衰变而出现自辐照老化效应。钚中氦行为是理解钚自辐照老化效应的一个基础和前提。运用分子动力学模拟技术,计算研究了钚中缺陷行为、氦与缺陷的相互作用、氦泡的初始形核过程、氦泡的长大过程以及氦泡对钚材料宏观性能的影响等。其中,钚-钚、钚-氦和氦-氦相互作用势分别采用修正嵌入原子多体势(modified embedded atom method,MEAM)、Morse对势和Lennard-Jones对势。主要的计算结果表明,氦原子与空位的结合能较大,在钚的自辐照过程中,两者易于结合并形成氦-空位团簇,成为氦泡的前驱体;氦泡可通过冲出位错环的机制而长大;氦泡的压力在GPa量级,且氦泡引起的基体膨胀很小。
基金Project(10776023)supported by the National Natural Science Foundation of China
文摘The plastic deformation processes of magnesium alloys near a void at atomic scale level were examined through molecular dynamics(MD)simulation.The modified embedded atom method(MEAM)potentials were employed to characterize the interaction between atoms of the magnesium alloy specimen with only a void.The void growth and crystal failure processes for hexagonal close-packed(hcp)structure were observed.The calculating results reveal that the deformation mechanism near a void in magnesium alloy is a complex process.The passivation around the void,dislocation emission,and coalescence of the void and micro-cavities lead to rapid void growth.
基金the National Key Research and Development Program of China(Grant No.2019YF40705400)National Natural Science Foundation of China(Grant Nos.51535005,51731006,and 51771093)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Me-chanical Structures(Grant Nos.MCMS-I-0418K01,MCMS-I-0419K01)the Fundamental Research Funds for the Central Universities(Grant Nos.NZ2020001,NC2018001,NP2019301,NJ20I 9002,and 30919011295)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Nb-doped TiAl alloys exhibit excellent mechanical properties at high temperatures,and the underlying mechanism and optimal doping amount remain elusive.Molecular dynamics simulation is helpful to clarify these problems,but most of the existing interatomic potentials are limited to the Ti-Al binary system and lack interatomic potentials for doped alloys.Here,an intera-tomic potential of Nb-Al-Ti ternary systems based on the modified embedded-atom method was developed.The ternary potential can accurately predict the structure and thermodynamic properties of the Nb-Al-Ti system.The potential shows that the optimal Nb content for high-temperature strength-ductility synergy of TiAl single crystals is 8%,consistent with the amount of miracle synthesis of TiAl single crystals.Tensile simulations further show that the developed potential can make an effective prediction at high temperatures,indicating the potential for the development and applications of high-temperature Nb-Al-Ti ternary systems.
文摘本文采用基于密度泛函理论发展的嵌入原子方法,推导了由半经验函数嵌入能和排斥势所表达的表面晶格动力学矩阵公式,以CU(100)面为例,得到了该面三个主要对称方向的色散关系.其中,沿 FX 方向的瑞利声子色散曲线与新近的电子能量损失谱所得实验结果相比,符合较好.文中还讨论了一些表面模的局域程度以及振动方式.
基金Project(20403004) supported by the National Nature Science Foundation of China
文摘Using embedded-atom-method potential for Pd and MORSE potential for the interaction between H and Pd atoms, the adsorption properties of H atoms on Pd (211), (311) and (511) stepped defective surfaces were calculated systematically. For Pd (311) surface, it is found that the four-fold hollow sites H4 are the preferable sites for H atoms being adsorbed on these Pd defective surfaces. The sites H4 are the most stable adsorbed sites and the three-fold hollow sites Hf and Hh are metastable ones. The calculated results are in reasonable agreement with the HREELS experiment results. For the (211) and (511) stepped defective surfaces of Pd, our calculation shows that the most stable adsorption sites are H5 and H2 respectively, both of them are four fold hollow sites.
