Molecular dynamics simulation was used to simulate the thermodynamic properties of three binary alloys,Pb-Ag （1：1）,Pb-Ag （4：1）,and Pb-Ag （9：1）.The energy functions,such as excess free energy,cohesive energy,a...Molecular dynamics simulation was used to simulate the thermodynamic properties of three binary alloys,Pb-Ag （1：1）,Pb-Ag （4：1）,and Pb-Ag （9：1）.The energy functions,such as excess free energy,cohesive energy,and formation energy,were calculated.The calculated values agree well with the experimental ones.The atomic interactions were analyzed in macroscopic and microcosmic views and both are consistent well.展开更多
Molecular dynamics(MD) simulations are performed to investigate the effects of stress on generalized stacking fault(GSF) energy of three fcc metals(Cu, Al, and Ni). The simulation model is deformed by uniaxial tension...Molecular dynamics(MD) simulations are performed to investigate the effects of stress on generalized stacking fault(GSF) energy of three fcc metals(Cu, Al, and Ni). The simulation model is deformed by uniaxial tension or compression in each of [111], [11-2], and [1-10] directions, respectively, before shifting the lattice to calculate the GSF curve. Simulation results show that the values of unstable stacking fault energy(γusf), stable stacking fault energy(γsf), and unstable twin fault energy(γutf) of the three elements can change with the preloaded tensile or compressive stress in different directions.The ratio of γsf/γusf, which is related to the energy barrier for full dislocation nucleation, and the ratio of γutf/γusf, which is related to the energy barrier for twinning formation are plotted each as a function of the preloading stress. The results of this study reveal that the stress state can change the energy barrier of defect nucleation in the crystal lattice, and thereby can play an important role in the deformation mechanism of nanocrystalline material.展开更多
The structural defects of L10 FePt are investigated by the molecular dynamics (MD) with a modified analytic embedded-atom method (MAEAM). The L10 ordered structure of FePt is relaxed from a trial fcc structure. The de...The structural defects of L10 FePt are investigated by the molecular dynamics (MD) with a modified analytic embedded-atom method (MAEAM). The L10 ordered structure of FePt is relaxed from a trial fcc structure. The defect formation energies are calculated. The vacancy formation energies of Fe and Pt are 1.89 eV and 2.11 eV respectively. The antisite formation energy of Fe in Pt sublattice is 0.35 eV. The antisite formation energy of Pt in Fe sublattice is 0.09 eV. The tendency of the vacancy formation energy is in agreement with other calculation. The point defect structure types are Pt antisite in rich-Pt side and Fe antisite in rich-Fe side.展开更多
This paper studies the coalescence of heteroclusters Au767 and Ag767 by using molecular dynamics with the embedded atom method, where layer atomic energy is employed to describe the potential energy variation of per a...This paper studies the coalescence of heteroclusters Au767 and Ag767 by using molecular dynamics with the embedded atom method, where layer atomic energy is employed to describe the potential energy variation of per atom in different layers along radial direction. The results show that the coalescence is driven by releasing the atomic energy of the coalesced zone. The deformation, which is induced by substitutional and vacancy diffusion during the coalescence, makes the coalesced cluster disorder. If the summation of the thermal energy and the released atomic energy is large enough to keep the disorder state, the clusters form a metastable liquid droplet; otherwise, the clusters coalesce into a solid cluster when the coalesced cluster reaches the equilibrium state, and the coalesced cluster experiences liquid to solid ordering changes during the coalescence of a solid Au767 with a liquid Ag767 and a liquid Au767 with a liquid Ag767. The centre of figure of the cluster system is shifted during the coalescence process, and higher coalescence temperature causes larger shift degree.展开更多
The embedded-atom method(EAM)is used to study the behavior of helium in meta-ls.By fitting the measured parameters such as the activation energy and the heat of solution,the EAM potentials of helium in nickel are extr...The embedded-atom method(EAM)is used to study the behavior of helium in meta-ls.By fitting the measured parameters such as the activation energy and the heat of solution,the EAM potentials of helium in nickel are extracted.Based upon the EAM potentials,thebinding energy and the self-trapping of helium in nickel are investigated with molecular dynam-ics simulation.展开更多
The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the （5s4p3d4f...The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the （5s4p3d4f）/[3s3p2d2f] contraction basis sets, and the cores are approximated with the relativistic effective core potential. The results show that the ground electronic state is x^9∑g＋. The pair potential data are fitted with a Murrell-Sorbie analytical potential function. The U-U embedded atom method （EAM） interatomic potential is determined based on the generalized gradient approximation calculation within the framework of the density functional theory using Perdew-Burke-Ernzerhof exchange-correlation functional at the spin-polarized level. The physical properties, such as the cohesive energy, the lattice constant, the bulk modulus, the shear modulus, the sc/fec relative energy, the hep/fce rela- tive energy, the shear modulus and the monovacaney formation energy are used to evaluate the EAM potential parameters. The U-U pair potential determined by the first principle calculations is in agreement with that defined by the EAM potential parameters. The EAM calculated formation energy of the monovacancy in the fee structure is also found to be in close agreement with DFT calculation.展开更多
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
原子间相互作用势是凝聚态物质在原子尺度上进行计算机模拟的基础,特别是用分子动力学和Monte Carlo方法对凝聚态物质的性质和过程进行模拟时,合适的原子间相互作用势是得到有意义的结果的前提和条件．可依据不同类型的相互作用如共价...原子间相互作用势是凝聚态物质在原子尺度上进行计算机模拟的基础,特别是用分子动力学和Monte Carlo方法对凝聚态物质的性质和过程进行模拟时,合适的原子间相互作用势是得到有意义的结果的前提和条件．可依据不同类型的相互作用如共价键、离子键、金属键和Van der Waals力等构建不同类型的原子间相互作用势,而且同一类型的相互作用也因所处理的性质或过程(如体积、表面、团簇、缺陷等)不同所采用的形式也不相同,这样就构建了大量的各种形式的原子间相互作用势．本文对凝聚态的计算机模拟中常用的原子间相互作用势进行分类介绍和简要的评述．展开更多
基金supported by the National Natural Science Foundation of China-Yunnan United Foundation (No. U0837604)
文摘Molecular dynamics simulation was used to simulate the thermodynamic properties of three binary alloys,Pb-Ag （1：1）,Pb-Ag （4：1）,and Pb-Ag （9：1）.The energy functions,such as excess free energy,cohesive energy,and formation energy,were calculated.The calculated values agree well with the experimental ones.The atomic interactions were analyzed in macroscopic and microcosmic views and both are consistent well.
基金supported by Australia Research Council Discovery Projects(Grant No.DP130103973)financially supported by the China Scholarship Council(CSC)
文摘Molecular dynamics(MD) simulations are performed to investigate the effects of stress on generalized stacking fault(GSF) energy of three fcc metals(Cu, Al, and Ni). The simulation model is deformed by uniaxial tension or compression in each of [111], [11-2], and [1-10] directions, respectively, before shifting the lattice to calculate the GSF curve. Simulation results show that the values of unstable stacking fault energy(γusf), stable stacking fault energy(γsf), and unstable twin fault energy(γutf) of the three elements can change with the preloaded tensile or compressive stress in different directions.The ratio of γsf/γusf, which is related to the energy barrier for full dislocation nucleation, and the ratio of γutf/γusf, which is related to the energy barrier for twinning formation are plotted each as a function of the preloading stress. The results of this study reveal that the stress state can change the energy barrier of defect nucleation in the crystal lattice, and thereby can play an important role in the deformation mechanism of nanocrystalline material.
基金Projects(50541036, 50371026) supported by the National Natural Science Foundation of China
文摘The structural defects of L10 FePt are investigated by the molecular dynamics (MD) with a modified analytic embedded-atom method (MAEAM). The L10 ordered structure of FePt is relaxed from a trial fcc structure. The defect formation energies are calculated. The vacancy formation energies of Fe and Pt are 1.89 eV and 2.11 eV respectively. The antisite formation energy of Fe in Pt sublattice is 0.35 eV. The antisite formation energy of Pt in Fe sublattice is 0.09 eV. The tendency of the vacancy formation energy is in agreement with other calculation. The point defect structure types are Pt antisite in rich-Pt side and Fe antisite in rich-Fe side.
基金supported by the National Natural Science Foundation of China (Grant No 50374027)the program for New Century Excellent Talents in University of China (Grant No NCET-06-0289)the 111 project of China (Grant No B07015)
文摘This paper studies the coalescence of heteroclusters Au767 and Ag767 by using molecular dynamics with the embedded atom method, where layer atomic energy is employed to describe the potential energy variation of per atom in different layers along radial direction. The results show that the coalescence is driven by releasing the atomic energy of the coalesced zone. The deformation, which is induced by substitutional and vacancy diffusion during the coalescence, makes the coalesced cluster disorder. If the summation of the thermal energy and the released atomic energy is large enough to keep the disorder state, the clusters form a metastable liquid droplet; otherwise, the clusters coalesce into a solid cluster when the coalesced cluster reaches the equilibrium state, and the coalesced cluster experiences liquid to solid ordering changes during the coalescence of a solid Au767 with a liquid Ag767 and a liquid Au767 with a liquid Ag767. The centre of figure of the cluster system is shifted during the coalescence process, and higher coalescence temperature causes larger shift degree.
基金The project supported by the National Natural Science Foundation of China
文摘The embedded-atom method(EAM)is used to study the behavior of helium in meta-ls.By fitting the measured parameters such as the activation energy and the heat of solution,the EAM potentials of helium in nickel are extracted.Based upon the EAM potentials,thebinding energy and the self-trapping of helium in nickel are investigated with molecular dynam-ics simulation.
文摘The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the （5s4p3d4f）/[3s3p2d2f] contraction basis sets, and the cores are approximated with the relativistic effective core potential. The results show that the ground electronic state is x^9∑g＋. The pair potential data are fitted with a Murrell-Sorbie analytical potential function. The U-U embedded atom method （EAM） interatomic potential is determined based on the generalized gradient approximation calculation within the framework of the density functional theory using Perdew-Burke-Ernzerhof exchange-correlation functional at the spin-polarized level. The physical properties, such as the cohesive energy, the lattice constant, the bulk modulus, the shear modulus, the sc/fec relative energy, the hep/fce rela- tive energy, the shear modulus and the monovacaney formation energy are used to evaluate the EAM potential parameters. The U-U pair potential determined by the first principle calculations is in agreement with that defined by the EAM potential parameters. The EAM calculated formation energy of the monovacancy in the fee structure is also found to be in close agreement with DFT calculation.
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。
文摘原子间相互作用势是凝聚态物质在原子尺度上进行计算机模拟的基础,特别是用分子动力学和Monte Carlo方法对凝聚态物质的性质和过程进行模拟时,合适的原子间相互作用势是得到有意义的结果的前提和条件．可依据不同类型的相互作用如共价键、离子键、金属键和Van der Waals力等构建不同类型的原子间相互作用势,而且同一类型的相互作用也因所处理的性质或过程(如体积、表面、团簇、缺陷等)不同所采用的形式也不相同,这样就构建了大量的各种形式的原子间相互作用势．本文对凝聚态的计算机模拟中常用的原子间相互作用势进行分类介绍和简要的评述．
