This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable posi...This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature （lower than 200 K for the Ag200Col cluster）. The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for （AgCo）2m clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the cluster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.展开更多
Taking an image of their structure and a movie of their dynamics of small quantum systems have always been a dream of physicists and chemists. Laser-induced Coulomb explosion imaging(CEI) provides a great opportunity ...Taking an image of their structure and a movie of their dynamics of small quantum systems have always been a dream of physicists and chemists. Laser-induced Coulomb explosion imaging(CEI) provides a great opportunity to make this dream a reality for small molecules or their aggregation — clusters. The method is unique for identifying the atomic locations with angstrom spatial resolution and capturing the structural evolution with a femtosecond time scale, in particular for imaging transient state products. This review summarizes the determination of three-dimensional equilibrium geometry of molecules and molecular cluster system through the reconstruction from the fragments momenta, and also shows that the dissociation dynamics on the complex potential energy surface can be tracked in real-time with the ultrafast CEI(UCEI).Furthermore, the detailed measurement and analysis procedures of the CEI, theoretical methods, exemplary results, and future perspectives of the technique are described.展开更多
构建了系列球形中空结构的纳米线(NW),采用分子动力学(MD)对每个模型300个不同初始态的样本开展拉伸形变模拟。并利用基于密度的噪声应用空间聚类(density-based spatial clustering of applications with noise,DBSCAN)机器学习算法,...构建了系列球形中空结构的纳米线(NW),采用分子动力学(MD)对每个模型300个不同初始态的样本开展拉伸形变模拟。并利用基于密度的噪声应用空间聚类(density-based spatial clustering of applications with noise,DBSCAN)机器学习算法,获得了初始滑移面的位置。基于大数据统计,分析了初始滑移位置分布以及断裂位置分布两者之间的相关性。研究结果表明:当内部中空半径较小时,断裂位置分布形成于塑性形变阶段,初始滑移分布与断裂位置分布之间无显著的相关性;但是对于脆性特征明显的大中空半径的NW,高能内表面诱导产生的滑移面迅速积累,产生颈缩并导致最终的断裂。因此当内部中空结构达到一定尺寸时初始滑移位置的分布与最终断裂位置的分布之间有明确的因果关系。展开更多
The synergy effect of alloy elements in bimetallic clusters can be used to tune the chemical and physical properties. Research on the influences of alloy concentration and distribution on the frozen structure of bimet...The synergy effect of alloy elements in bimetallic clusters can be used to tune the chemical and physical properties. Research on the influences of alloy concentration and distribution on the frozen structure of bimetallic clusters plays a key rolc in exploring new structural materials. In this paper, we study the influence of Ag concentration on the frozen structure of the （AgCo）561 cluster by using molecular dynamics simulation with a general embedded atom method. The results indicate that tt^e structure and chemical ordering of the （AgCo）561 cluster are strongly related to Ag concentration. Hcp-icosahedron structural transformation in the frozen （CoAg）561 cluster can be induced by changing Ag concentration. The chemical ordering also transforms to Janus-like Co Ag from core-shell Co-Ag.展开更多
This paper studies the melting of icosahedral Ag-Pd bimetallic clusters by using molecular dynamics with the embedded atom method. It finds that the mixed Ag-Pd cluster shows an irregular phenomenon before melting, i....This paper studies the melting of icosahedral Ag-Pd bimetallic clusters by using molecular dynamics with the embedded atom method. It finds that the mixed Ag-Pd cluster shows an irregular phenomenon before melting, i.e., the atomic energy decreases with the increase of temperature. It indicates that the segregation of Ag atoms results in this phenomenon by analysing atomic radius distribution. Since the surface energy of Ag is lower than that of Pd, this leads to the result that the decreased energy by the Ag atomic segregation is larger than the increased energy by the heating. This provides a new method to obtain irregular thermodynamic properties.展开更多
Density functional based tight binding (DFTB) model is employed to study the sp3-to-sp2 transformation of diamond-like carbon at elevated temperatures. The understanding could lead to the direct-growth of graphene on ...Density functional based tight binding (DFTB) model is employed to study the sp3-to-sp2 transformation of diamond-like carbon at elevated temperatures. The understanding could lead to the direct-growth of graphene on a wide variety of substrates.展开更多
基金supported by the National Natural Science Foundation of China(Grant No 50374027)the program for New Century Excellent Talents in University(Grant No NCET-06-0289)the 111 project of China(Grant No B07015)
文摘This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature （lower than 200 K for the Ag200Col cluster）. The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for （AgCo）2m clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the cluster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.
基金Project partially supported by the National Key Research and Development Program of China (Grant Nos. 2019YFA0307700)the National Natural Science Foundation of China (Grant Nos. 12004133, 12074143, 12134005, and 11904210)China Postdoctoral Science Foundation (Grant No. 2021M691220)。
文摘Taking an image of their structure and a movie of their dynamics of small quantum systems have always been a dream of physicists and chemists. Laser-induced Coulomb explosion imaging(CEI) provides a great opportunity to make this dream a reality for small molecules or their aggregation — clusters. The method is unique for identifying the atomic locations with angstrom spatial resolution and capturing the structural evolution with a femtosecond time scale, in particular for imaging transient state products. This review summarizes the determination of three-dimensional equilibrium geometry of molecules and molecular cluster system through the reconstruction from the fragments momenta, and also shows that the dissociation dynamics on the complex potential energy surface can be tracked in real-time with the ultrafast CEI(UCEI).Furthermore, the detailed measurement and analysis procedures of the CEI, theoretical methods, exemplary results, and future perspectives of the technique are described.
文摘构建了系列球形中空结构的纳米线(NW),采用分子动力学(MD)对每个模型300个不同初始态的样本开展拉伸形变模拟。并利用基于密度的噪声应用空间聚类(density-based spatial clustering of applications with noise,DBSCAN)机器学习算法,获得了初始滑移面的位置。基于大数据统计,分析了初始滑移位置分布以及断裂位置分布两者之间的相关性。研究结果表明:当内部中空半径较小时,断裂位置分布形成于塑性形变阶段,初始滑移分布与断裂位置分布之间无显著的相关性;但是对于脆性特征明显的大中空半径的NW,高能内表面诱导产生的滑移面迅速积累,产生颈缩并导致最终的断裂。因此当内部中空结构达到一定尺寸时初始滑移位置的分布与最终断裂位置的分布之间有明确的因果关系。
基金supported by the Science Foundation of Chongqing Committee of Education of China (Grant No. KJ111206)the Fund of Chongqing University of Arts and Sciences (Grant No. Z2011RCYJ05)
文摘The synergy effect of alloy elements in bimetallic clusters can be used to tune the chemical and physical properties. Research on the influences of alloy concentration and distribution on the frozen structure of bimetallic clusters plays a key rolc in exploring new structural materials. In this paper, we study the influence of Ag concentration on the frozen structure of the （AgCo）561 cluster by using molecular dynamics simulation with a general embedded atom method. The results indicate that tt^e structure and chemical ordering of the （AgCo）561 cluster are strongly related to Ag concentration. Hcp-icosahedron structural transformation in the frozen （CoAg）561 cluster can be induced by changing Ag concentration. The chemical ordering also transforms to Janus-like Co Ag from core-shell Co-Ag.
基金Project supported by Chongqing Committee of Education of China (Grant No. KJ081208)
文摘This paper studies the melting of icosahedral Ag-Pd bimetallic clusters by using molecular dynamics with the embedded atom method. It finds that the mixed Ag-Pd cluster shows an irregular phenomenon before melting, i.e., the atomic energy decreases with the increase of temperature. It indicates that the segregation of Ag atoms results in this phenomenon by analysing atomic radius distribution. Since the surface energy of Ag is lower than that of Pd, this leads to the result that the decreased energy by the Ag atomic segregation is larger than the increased energy by the heating. This provides a new method to obtain irregular thermodynamic properties.
基金Supported by the Natural Science Foundation of China under Grant Nos 10575012 and 10435020, the Science Foundation of Beijing, and the Science Foundation of the Ministry of Education of China.
文摘Density functional based tight binding (DFTB) model is employed to study the sp3-to-sp2 transformation of diamond-like carbon at elevated temperatures. The understanding could lead to the direct-growth of graphene on a wide variety of substrates.
