We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blu...We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.展开更多
Adsorption behavior of Fe atoms on a metal-free naphthalocyanine（H2Nc） monolayer on Ag（111） surface at room temperature has been investigated using scanning tunneling microscopy combined with density functional th...Adsorption behavior of Fe atoms on a metal-free naphthalocyanine（H2Nc） monolayer on Ag（111） surface at room temperature has been investigated using scanning tunneling microscopy combined with density functional theory（DFT）based calculations. We found that the Fe atoms were adsorbed on the centers of H2Nc molecules and formed Fe–H2Nc complexes at low coverage. DFT calculations show that Fe sited in the center of the molecule is the most stable configuration, in good agreement with the experimental observations. After an Fe–H2Nc complex monolayer was formed, the extra Fe atoms self-assembled to Fe clusters of uniform size and adsorbed dispersively at the interstitial positions of Fe–H2Nc complex monolayer. Therefore, the H2Nc monolayer grown on Ag（111） could be a good template to grow dispersed magnetic metal atoms and clusters at room temperature for further investigation of their magnetism-related properties.展开更多
Atomic switches can be used in future nanodevices and to realize conceptually novel electronics in new types of computer architecture because of their simple structure, ease of operation, stability, and reliability. T...Atomic switches can be used in future nanodevices and to realize conceptually novel electronics in new types of computer architecture because of their simple structure, ease of operation, stability, and reliability. The atomic switch is a single solid-state switch with inherent learning abilities that exhibits various nonlinear behaviors with network devices. However, previous studies focused on experiments and nonvolatile memory applications, and studies on the application of the physical properties of the atomic switch in computing were nonexistent. Therefore, we present a simple behavioral model of a molecular gap-type atomic switch that can be included in a simulator. The model was described by three simple equations that reproduced the bistability using a double-well potential and was able to easily be transferred to a simulator using arbitrary numerical values and be integrated into HSPICE. Simulations using the experimental parameters of the proposed atomic switch agreed with the experimental results. This model will allow circuit designers to explore new architectures, contributing to the development of new computing methods.展开更多
To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,...To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,Al-Al and Cu-Cu combinations fabricated through collision welding using molecular dynamic(MD)simulation.The atomic diffusion behaviors are compared between similar metal combinations(Al-Al,Cu-Cu)and dissimilar metal combinations(Al-Cu).By combining the simulation results and classical diffusion theory,the diffusion coefficients for similar and dissimilar metal material combinations under different velocity conditions are obtained.The effects of material combinations and collision velocity on diffusion behaviors are also discussed.The diffusion behaviors of dissimilar material combinations strongly depend on the transverse velocity,whereas those of the similar material combinations are more dependent on the longitudinal velocity.These findings can provide guidance for optimizing welding parameters.展开更多
It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference...It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference.In this contribution,a qualitatively and graphically characterizing approach to the diffusion behavior of interstitial nonmetallic atoms diffusing along the neighboring octahedra in MPEAs was explored intensively.For this purpose,the C atom diffusing along the neighboring octahedra in FCC_CoNiV MPEA with(V1.0000)1a(Co0.4445Ni0.4444V0.1111)3c,a constant ordered occupying configuration predicted in our previous paper,was demonstrated in detail.Six distinct diffusion paths along[110],[101],and[011]directions on XY,XZ,and YZ planes of FCC_CoNiV MPEA with forward and backward diffusion directions were explored one by one,respectively.The diffusion energy barrier,diffusion coefficient,diffusion constant,and activation energy were derived by employing first-principles calculations based on density functional theory alongside the Climbing Image Nudged Elastic Band method.Unlike diffusing behavior in pure metallic elements,the non-periodic diffusion energy barrier waves are revealed for the real FCC_CoNiV MPEA structure.The significant variations in the diffusion energy barriers are influenced by the atomic environment,particularly the interaction between V and C atoms,which enhances the localization of electrons and increases the overall diffusion energy barrier.The energy barriers show similar trends along six paths,but significant variations occur across different octahedral sites.展开更多
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301503the National Natural Science Foundation of China under Grant Nos 11674358 and 11434015the Instrument Project of the Chinese Academy of Sciences under Grant No YJKYYQ20170025
文摘We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.
基金supported by the National Natural Science Foundation of China(Grant Nos.61390501,51325204,and 11204361)the National Basic Research Program of China(Grant Nos.2011CB808401 and 2011CB921702)+1 种基金the National Key Scientific Instrument and Equipment Development Project of China(Grant No.2013YQ1203451)the National Supercomputing Center in Tianjin,China,and the Chinese Academy of Sciences
文摘Adsorption behavior of Fe atoms on a metal-free naphthalocyanine（H2Nc） monolayer on Ag（111） surface at room temperature has been investigated using scanning tunneling microscopy combined with density functional theory（DFT）based calculations. We found that the Fe atoms were adsorbed on the centers of H2Nc molecules and formed Fe–H2Nc complexes at low coverage. DFT calculations show that Fe sited in the center of the molecule is the most stable configuration, in good agreement with the experimental observations. After an Fe–H2Nc complex monolayer was formed, the extra Fe atoms self-assembled to Fe clusters of uniform size and adsorbed dispersively at the interstitial positions of Fe–H2Nc complex monolayer. Therefore, the H2Nc monolayer grown on Ag（111） could be a good template to grow dispersed magnetic metal atoms and clusters at room temperature for further investigation of their magnetism-related properties.
文摘Atomic switches can be used in future nanodevices and to realize conceptually novel electronics in new types of computer architecture because of their simple structure, ease of operation, stability, and reliability. The atomic switch is a single solid-state switch with inherent learning abilities that exhibits various nonlinear behaviors with network devices. However, previous studies focused on experiments and nonvolatile memory applications, and studies on the application of the physical properties of the atomic switch in computing were nonexistent. Therefore, we present a simple behavioral model of a molecular gap-type atomic switch that can be included in a simulator. The model was described by three simple equations that reproduced the bistability using a double-well potential and was able to easily be transferred to a simulator using arbitrary numerical values and be integrated into HSPICE. Simulations using the experimental parameters of the proposed atomic switch agreed with the experimental results. This model will allow circuit designers to explore new architectures, contributing to the development of new computing methods.
基金supported by the Scientific Research Project of Hunan Provincial Department of Education(22C0642).
文摘To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,Al-Al and Cu-Cu combinations fabricated through collision welding using molecular dynamic(MD)simulation.The atomic diffusion behaviors are compared between similar metal combinations(Al-Al,Cu-Cu)and dissimilar metal combinations(Al-Cu).By combining the simulation results and classical diffusion theory,the diffusion coefficients for similar and dissimilar metal material combinations under different velocity conditions are obtained.The effects of material combinations and collision velocity on diffusion behaviors are also discussed.The diffusion behaviors of dissimilar material combinations strongly depend on the transverse velocity,whereas those of the similar material combinations are more dependent on the longitudinal velocity.These findings can provide guidance for optimizing welding parameters.
基金supported by the National Natural Science Foundation of China(50971043 and 51171046)the Key Research and Development Program of China(CISRI-21T62450ZD)+1 种基金the Natural Science Foundation of Fujian Province(2014J01176,2018J01754,and 2021J01590)the Student Research and Training Program(SRTP)of Fuzhou University(27297).
文摘It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference.In this contribution,a qualitatively and graphically characterizing approach to the diffusion behavior of interstitial nonmetallic atoms diffusing along the neighboring octahedra in MPEAs was explored intensively.For this purpose,the C atom diffusing along the neighboring octahedra in FCC_CoNiV MPEA with(V1.0000)1a(Co0.4445Ni0.4444V0.1111)3c,a constant ordered occupying configuration predicted in our previous paper,was demonstrated in detail.Six distinct diffusion paths along[110],[101],and[011]directions on XY,XZ,and YZ planes of FCC_CoNiV MPEA with forward and backward diffusion directions were explored one by one,respectively.The diffusion energy barrier,diffusion coefficient,diffusion constant,and activation energy were derived by employing first-principles calculations based on density functional theory alongside the Climbing Image Nudged Elastic Band method.Unlike diffusing behavior in pure metallic elements,the non-periodic diffusion energy barrier waves are revealed for the real FCC_CoNiV MPEA structure.The significant variations in the diffusion energy barriers are influenced by the atomic environment,particularly the interaction between V and C atoms,which enhances the localization of electrons and increases the overall diffusion energy barrier.The energy barriers show similar trends along six paths,but significant variations occur across different octahedral sites.
