The microstructure characteristic of the cold-rolled deformed nanocrystalline nickel metal is studied by transmission electron microscopy. The results show that there are step structures nearby the grain boundary （CB...The microstructure characteristic of the cold-rolled deformed nanocrystalline nickel metal is studied by transmission electron microscopy. The results show that there are step structures nearby the grain boundary （CB）, and the contrast of stress field in front of the step corresponds to the step in the shape. It is indicated that the interaction between twins and dislocations is not a necessary condition to realizing the deformation. In the later stage of the deformation when the grain size becomes about lOOnm, the deformation can depend upon the moving of the boundary of the stack faults （SFs） which result from the partial dislocations emitted from CBs. However, when the size of SFs grows up, the local internal stress which is in front of the step gradually becomes higher. When this stress reaches a critical value which stops the gliding of the partial dislocations, the SFs will stop to grow up and leave a step structure behind.展开更多
Dependence of the thermal conductivity on the length of two armchair single-walled carbon nanotubes （SWNTs） is studied by the nonequilibrium molecular dynamics （MD） method with Brenner Ⅱ potential. The thermal co...Dependence of the thermal conductivity on the length of two armchair single-walled carbon nanotubes （SWNTs） is studied by the nonequilibrium molecular dynamics （MD） method with Brenner Ⅱ potential. The thermal conductivities are calculated for （5, 5） and （7, 7） SWNTs with lengths ranging from 22 to 155nm. The results show that the thermal conductivity of SWNTs is sensitive to the length and it does not converge to a finite value when the tube length increases up to 155nm, however it obeys a power law relation.展开更多
In this article, a brief summary of the up-to-date progress of metallic glass formation by ion mixing of metallic multilayers in the binary metal systems is first presented. Secondly, thermodynamic modeling of metalli...In this article, a brief summary of the up-to-date progress of metallic glass formation by ion mixing of metallic multilayers in the binary metal systems is first presented. Secondly, thermodynamic modeling of metallic glass formation is developed with special consideration of the interfacial free energy of the multilayers. Thirdly, results of molecular dynamics simulations for some representative systems are presented to show the calculation of the glass-forming ability directly from the inter-atomic potential of the binary metal systems.展开更多
一直以来,金属纳米材料有着非常重要的应用价值且受到广泛关注,金属团簇碰撞合并过程的研究成果对认清团簇的沉积和纳米金属膜及块体材料的形成有重要的意义。采用Johnson的嵌入原子势(Embeded atom method,EAM)模型并结合分子动力学模...一直以来,金属纳米材料有着非常重要的应用价值且受到广泛关注,金属团簇碰撞合并过程的研究成果对认清团簇的沉积和纳米金属膜及块体材料的形成有重要的意义。采用Johnson的嵌入原子势(Embeded atom method,EAM)模型并结合分子动力学模拟方法,模拟金原子团簇在不同的碰撞平动速度作用下的碰撞合并过程,仅给弹团簇一定大小的碰撞动能,迫使两个团簇产生相对速度并发生相互碰撞合并,研究在不同的碰撞平动速度下和不同的团簇大小下对团簇碰撞合并过程产生的影响及对碰撞合并之后新团簇的性质产生的影响。在进行模拟碰撞之前,先对团簇进行了"退火"处理,只模拟了同等尺度大小的两个金原子团簇之间的碰撞合并过程。展开更多
We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of...We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923 K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5-8 bonds, via prolate structures containing 3-4 bonds, to oblate structures containing 1-2 bonds.展开更多
The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on t...The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall,which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work,molecular dynamics(MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet's critical wetting properties considering the evaporation–condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results.展开更多
Deformation twinning is evidenced by transmission electron microscopy examinations in electrodeposited nanocrystalline （nc） Ni with mean grain size 25nm upon cryogenic rolling. Two twinning mechanisms are confirmed ...Deformation twinning is evidenced by transmission electron microscopy examinations in electrodeposited nanocrystalline （nc） Ni with mean grain size 25nm upon cryogenic rolling. Two twinning mechanisms are confirmed to operate in nc grains, i.e. heterogeneous formation via emission of partial dislocations from the grain boundary and homogeneous nucleation through dynamic overlapping of stacking faults, with the former being determined as the most proficient. Deformation twinning in nc Ni may be well interpreted in terms of molecular dynamics simulation based on generalized planar fault energy curves.展开更多
We observed the linear-to-zigzag structural phase transition of a ^40Ca^＋ crystal in a homemade linear Paul trap. The values of the total temperature of the ion crystals during the phase transition are derived using ...We observed the linear-to-zigzag structural phase transition of a ^40Ca^＋ crystal in a homemade linear Paul trap. The values of the total temperature of the ion crystals during the phase transition are derived using the molecular-dynamics（MD） simulation method. A series of simulations revealed that the ratio of the radial to axial secular frequencies has a dependence on the total temperature that obeys different functional forms for linear and zigzag structures, and the transition point occurs where these functions intersect; thus, the critical value of the ratio of secular frequencies that drives the structure phase transition can be derived.展开更多
The potential energy surface for the migration of an extra Ga atom on the GaAs（001） β2（2×4） surfuce was mapped out by performing calculations at the level of analytical bond-order potential. Based on this ca...The potential energy surface for the migration of an extra Ga atom on the GaAs（001） β2（2×4） surfuce was mapped out by performing calculations at the level of analytical bond-order potential. Based on this calculations, we found some lower-energy sites for the adsorption of an extra Ga atom in the surface, which were in agreement with the experimental data. Moreover, many possible pathways for an extra Ga atom diffusing in this surface were revealed. According to the relative energies of the possible pathways, the individual Ga adatoms preferably keep their diffusion in two pathways parallel to the As dimers. This result can be understood using the strain caused by the diffusing Ga atom in the pathways. In addition, the simulated kinetic processes of the extra Ga atom diffusing in different pathways at finite temperatures support the prediction from our calculated potential energy surface.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 50471086 and 50461001.
文摘The microstructure characteristic of the cold-rolled deformed nanocrystalline nickel metal is studied by transmission electron microscopy. The results show that there are step structures nearby the grain boundary （CB）, and the contrast of stress field in front of the step corresponds to the step in the shape. It is indicated that the interaction between twins and dislocations is not a necessary condition to realizing the deformation. In the later stage of the deformation when the grain size becomes about lOOnm, the deformation can depend upon the moving of the boundary of the stack faults （SFs） which result from the partial dislocations emitted from CBs. However, when the size of SFs grows up, the local internal stress which is in front of the step gradually becomes higher. When this stress reaches a critical value which stops the gliding of the partial dislocations, the SFs will stop to grow up and leave a step structure behind.
文摘Dependence of the thermal conductivity on the length of two armchair single-walled carbon nanotubes （SWNTs） is studied by the nonequilibrium molecular dynamics （MD） method with Brenner Ⅱ potential. The thermal conductivities are calculated for （5, 5） and （7, 7） SWNTs with lengths ranging from 22 to 155nm. The results show that the thermal conductivity of SWNTs is sensitive to the length and it does not converge to a finite value when the tube length increases up to 155nm, however it obeys a power law relation.
基金the National Natural Science Foundationof China !(No. 5 92 310 31194740 30 and 5 95 710 11)the Ministry of Science and T
文摘In this article, a brief summary of the up-to-date progress of metallic glass formation by ion mixing of metallic multilayers in the binary metal systems is first presented. Secondly, thermodynamic modeling of metallic glass formation is developed with special consideration of the interfacial free energy of the multilayers. Thirdly, results of molecular dynamics simulations for some representative systems are presented to show the calculation of the glass-forming ability directly from the inter-atomic potential of the binary metal systems.
文摘一直以来,金属纳米材料有着非常重要的应用价值且受到广泛关注,金属团簇碰撞合并过程的研究成果对认清团簇的沉积和纳米金属膜及块体材料的形成有重要的意义。采用Johnson的嵌入原子势(Embeded atom method,EAM)模型并结合分子动力学模拟方法,模拟金原子团簇在不同的碰撞平动速度作用下的碰撞合并过程,仅给弹团簇一定大小的碰撞动能,迫使两个团簇产生相对速度并发生相互碰撞合并,研究在不同的碰撞平动速度下和不同的团簇大小下对团簇碰撞合并过程产生的影响及对碰撞合并之后新团簇的性质产生的影响。在进行模拟碰撞之前,先对团簇进行了"退火"处理,只模拟了同等尺度大小的两个金原子团簇之间的碰撞合并过程。
基金Supported by the National Natural Science Foundation of China under Grant No 10274055, the Natural Science Foundation of Sichuan Education Bureau under Grant No 2004A181, and the Research Fund for the Doctoral Program of Yibin University under Grant No 2005B01.
文摘We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923 K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5-8 bonds, via prolate structures containing 3-4 bonds, to oblate structures containing 1-2 bonds.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0202401)the National Natural Science Foundation of China(Grant No.61705066)the Fundamental Research Funds for the Central Universities,China(Grant No.2017MS028)
文摘The microscopic stripe pillar is one of the most frequently adopted building blocks for hydrophobic substrates. However, at high temperatures the particles on the droplet surface readily evaporate and re-condense on the pillar sidewall,which makes the droplet highly unstable and undermines the overall hydrophobic performance of the pillar. In this work,molecular dynamics(MD) simulation of the simple liquid at a single stripe pillar edge defect is performed to characterize the droplet's critical wetting properties considering the evaporation–condensation effect. From the simulation results, the droplets slide down from the edge defect with a volume smaller than the critical value, which is attributed to the existence of the wetting layer on the stripe pillar sidewall. Besides, the analytical study of the pillar sidewall and wetting layer potential field distribution manifests the relation between the simulation parameters and the degree of the droplet pre-wetting, which agrees well with the MD simulation results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50471086, 50571110, 10472117, and 50021101, the National Key Basic Research and Development Programme of China under Grant. No 2004CB619305, the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX2-SW-L2, and the National Center for Nanoscience and Technology of China.
文摘Deformation twinning is evidenced by transmission electron microscopy examinations in electrodeposited nanocrystalline （nc） Ni with mean grain size 25nm upon cryogenic rolling. Two twinning mechanisms are confirmed to operate in nc grains, i.e. heterogeneous formation via emission of partial dislocations from the grain boundary and homogeneous nucleation through dynamic overlapping of stacking faults, with the former being determined as the most proficient. Deformation twinning in nc Ni may be well interpreted in terms of molecular dynamics simulation based on generalized planar fault energy curves.
基金Project supported by the National Basic Research Program of China(Grant Nos.2010CB832803 and 2012CB821301)the National Natural Science Foundation of China(Grant Nos.11004222 and 91121016)the Chinese Academy of Sciences
文摘We observed the linear-to-zigzag structural phase transition of a ^40Ca^＋ crystal in a homemade linear Paul trap. The values of the total temperature of the ion crystals during the phase transition are derived using the molecular-dynamics（MD） simulation method. A series of simulations revealed that the ratio of the radial to axial secular frequencies has a dependence on the total temperature that obeys different functional forms for linear and zigzag structures, and the transition point occurs where these functions intersect; thus, the critical value of the ratio of secular frequencies that drives the structure phase transition can be derived.
基金ACKNOWLEDGMENTS This work was supported by the Fund of University of Science and Technology of China, the Fund of Chinese Academy of Science, and the National Natural Science Foundation of China （No.50121202 and No.60176024）.
文摘The potential energy surface for the migration of an extra Ga atom on the GaAs（001） β2（2×4） surfuce was mapped out by performing calculations at the level of analytical bond-order potential. Based on this calculations, we found some lower-energy sites for the adsorption of an extra Ga atom in the surface, which were in agreement with the experimental data. Moreover, many possible pathways for an extra Ga atom diffusing in this surface were revealed. According to the relative energies of the possible pathways, the individual Ga adatoms preferably keep their diffusion in two pathways parallel to the As dimers. This result can be understood using the strain caused by the diffusing Ga atom in the pathways. In addition, the simulated kinetic processes of the extra Ga atom diffusing in different pathways at finite temperatures support the prediction from our calculated potential energy surface.
