Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic orde...Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic ordering and surface segregation effects in Pd-Rh particles with compositions 1:3, 1:1 and 3:1 containing up to 201 atoms(ca. 1.7 nm). The obtained data are used to reliably optimise energetically preferred atomic orderings in inaccessible by DFT Pd-Rh particles containing thousands of atoms and exhibiting sizes exceeding 5 nm, which are typical for catalytic metal particles. It is outlined, how segregation effects on the surface arrangement of Pd-Rh nanoalloy catalysts induced by adsorbates can be evaluated in a simple way within the present modelling setup.展开更多
This paper derives the expressions for the ordering degree and the modulation factor of A and B atoms in AXB1-xC epilayers of ternary III-V semiconductor alloys. Using these expressions, it identifies quantitatively t...This paper derives the expressions for the ordering degree and the modulation factor of A and B atoms in AXB1-xC epilayers of ternary III-V semiconductor alloys. Using these expressions, it identifies quantitatively the alternating atom-enhanced planes, compositional modulations, atomic ordering degree on the group-III sublattices and the fine structure of NMR spectra.展开更多
The mechanism involving the effect of disorder/order transformation on the environmental embrittlement in gaseous H2 is summarized. It is shown that there is no hydrogen embrittlement in disordered state of Kurnakov t...The mechanism involving the effect of disorder/order transformation on the environmental embrittlement in gaseous H2 is summarized. It is shown that there is no hydrogen embrittlement in disordered state of Kurnakov type intermetallics in gaseous H2. However, the H2-induced environmental embrittlement for the ordered alloy having identical chemical composition becomes severer as the degree of the order increases. The results of testing on the ion gage turned on and off during tensile testing show that the more sensitive to H2-induced hydrogen embrittlement for ordered alloy than disordered one is attributed to the fact that atomic ordering may accelerate the kinetics of the catalytic reaction to produce more atomic hydrogen. The results on simultaneous hydrogen charging show that disordered alloys embrittled as hydrogen atoms are forced into the material implying that the embrittlement of ordered alloy in gaseous H2 is also due to the acceleration of the kinetics of catalytic reaction. The above suggestion was further verified by the adsorption tests of Ni3Fe intermetallics powder. It is shown that the amount of chemically adsorbed hydrogen in ordered state is significantly larger than that adsorbed by the disordered alloy, indicating that the more sensitive to H2-induced embrittlement in the ordered state of alloy is essentially due to the accelerated catalytic reaction.展开更多
The major interface betweenβ-Mg_(3)Sn precipitate plate and theα-Mg matrix in a Mg-9.8wt.%alloy has been investigated using aberrationcorrected scanning transmission electron microscopy and first-principles calculat...The major interface betweenβ-Mg_(3)Sn precipitate plate and theα-Mg matrix in a Mg-9.8wt.%alloy has been investigated using aberrationcorrected scanning transmission electron microscopy and first-principles calculations.It is found that Sn atoms orderly distribute in the single layer of theα-Mg matrix immediately adjacent to the broad surface ofβat the early stage of ageing.These Sn atoms substitute Mg atoms located at the centers of equilateral triangles constituted by three Mg columns in the outmost layer ofβ.First-principles calculations suggest that the ordered Sn distribution is energetically favored and it not only decreases the interfacial energy of theβ-matrix interface but also hinders the occurrence of 1/3<01■0>αshear that thickens theβplate.展开更多
The disaccommodation of magnetic per- meability,specific magnetization and linear magnetostriction of amorphous(Fe_xNi_(1-x))_(76)- Si_8B_(16)alloys were measured.It was found that the disaccommodation obtained at low...The disaccommodation of magnetic per- meability,specific magnetization and linear magnetostriction of amorphous(Fe_xNi_(1-x))_(76)- Si_8B_(16)alloys were measured.It was found that the disaccommodation obtained at lower temperature is a monotonically decreasing function of Fe content, however,a peak is observed at higher temperature. The experimental results are discussed on the basis of magnetostrictive interaction and atomic directional ordering.展开更多
The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an o...The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an optical lattice.In this paper,this phenomenon is demonstrated for the periodically trapped and coherently driven cold 87Rb atoms,where radiation damping might be much larger than that anticipated in previous proposals and become comparable with radiation pressure.Such an enhancement could be observed even at speeds of only a few meters per second with less than 1.0%absorption,making radiation damping experimentally accessible.展开更多
Thaditional implementation of sequential consistency in shared-memory systems requires memory accesses to be globally performed in program order. Based on an event ordering model for correct executions in shared-memor...Thaditional implementation of sequential consistency in shared-memory systems requires memory accesses to be globally performed in program order. Based on an event ordering model for correct executions in shared-memory systems, this paper proposes and proves that out-of-order execution does not influence the correctness of an execution providing certain condition is met. Simulation results show that out-of-order execution proposed in this paper is an effective way to improve the performance of a sequentially consistent shared-memory system.展开更多
基金financed by the Generalitat de Catalunya via a pre-doctoral grant 2018FI-B-00384the Operational program“Science and Education for Smart Growth”,project BG05M2OP001-2.009-0028 for funding his research stay in the University of Barcelona+2 种基金financial support by the Bulgarian Ministry of Education and Science under the National Research Programme“Low-carbon Energy for the Transportsupport by the Spanish grants PGC2018-093863-B-C22,CTQ2015-64618-RMDM-2017-0767 as well as by the grant 2017SGR13 of the Generalitat de Catalunya
文摘Pd-Rh nanoparticles are known to easily undergo surface restructuring in reactive environment. This study quantifies, with the help of density functional(DFT) calculations and a novel topological approach, atomic ordering and surface segregation effects in Pd-Rh particles with compositions 1:3, 1:1 and 3:1 containing up to 201 atoms(ca. 1.7 nm). The obtained data are used to reliably optimise energetically preferred atomic orderings in inaccessible by DFT Pd-Rh particles containing thousands of atoms and exhibiting sizes exceeding 5 nm, which are typical for catalytic metal particles. It is outlined, how segregation effects on the surface arrangement of Pd-Rh nanoalloy catalysts induced by adsorbates can be evaluated in a simple way within the present modelling setup.
基金Project supported by the National Natural Science Foundation of China (Grant No 60572177)CAUC Foundation (Grant No 05yk27s)
文摘This paper derives the expressions for the ordering degree and the modulation factor of A and B atoms in AXB1-xC epilayers of ternary III-V semiconductor alloys. Using these expressions, it identifies quantitatively the alternating atom-enhanced planes, compositional modulations, atomic ordering degree on the group-III sublattices and the fine structure of NMR spectra.
基金Project supported by the National Natural Science Foundation of China （Grant Nos.50371050, 59895157, 59681002, 59771007）
文摘The mechanism involving the effect of disorder/order transformation on the environmental embrittlement in gaseous H2 is summarized. It is shown that there is no hydrogen embrittlement in disordered state of Kurnakov type intermetallics in gaseous H2. However, the H2-induced environmental embrittlement for the ordered alloy having identical chemical composition becomes severer as the degree of the order increases. The results of testing on the ion gage turned on and off during tensile testing show that the more sensitive to H2-induced hydrogen embrittlement for ordered alloy than disordered one is attributed to the fact that atomic ordering may accelerate the kinetics of the catalytic reaction to produce more atomic hydrogen. The results on simultaneous hydrogen charging show that disordered alloys embrittled as hydrogen atoms are forced into the material implying that the embrittlement of ordered alloy in gaseous H2 is also due to the acceleration of the kinetics of catalytic reaction. The above suggestion was further verified by the adsorption tests of Ni3Fe intermetallics powder. It is shown that the amount of chemically adsorbed hydrogen in ordered state is significantly larger than that adsorbed by the disordered alloy, indicating that the more sensitive to H2-induced embrittlement in the ordered state of alloy is essentially due to the accelerated catalytic reaction.
基金financially National Natural Science Foundation of China(52101167 and 52071033)Natural Science Foundation Project of CQ(cstc2020jcyjmsxm X0832)+3 种基金the Fundamental Research Funds for the Central Universities(2020CDJ-LHZZ-085)State Key Laboratory of Powder Metallurgy,Central South University,Changsha,Chinasupported in part by the High Performance Computing center of the Central South UniversityJFN acknowledges the support from the Australian Research Council and computational resources provided by the Australian Government through Pawsey under the National Computational Merit Allocation Scheme and the use of the National Computational Infrastructure。
文摘The major interface betweenβ-Mg_(3)Sn precipitate plate and theα-Mg matrix in a Mg-9.8wt.%alloy has been investigated using aberrationcorrected scanning transmission electron microscopy and first-principles calculations.It is found that Sn atoms orderly distribute in the single layer of theα-Mg matrix immediately adjacent to the broad surface ofβat the early stage of ageing.These Sn atoms substitute Mg atoms located at the centers of equilateral triangles constituted by three Mg columns in the outmost layer ofβ.First-principles calculations suggest that the ordered Sn distribution is energetically favored and it not only decreases the interfacial energy of theβ-matrix interface but also hinders the occurrence of 1/3<01■0>αshear that thickens theβplate.
文摘The disaccommodation of magnetic per- meability,specific magnetization and linear magnetostriction of amorphous(Fe_xNi_(1-x))_(76)- Si_8B_(16)alloys were measured.It was found that the disaccommodation obtained at lower temperature is a monotonically decreasing function of Fe content, however,a peak is observed at higher temperature. The experimental results are discussed on the basis of magnetostrictive interaction and atomic directional ordering.
基金This work is supported by the National Natural Science Foundation of China(11104112)the National Basic Research Program of China(2011CB921603)the CRUI-British Council 2011 Exchange Program and the Fondo di Ateneo of the Brescia University
文摘The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an optical lattice.In this paper,this phenomenon is demonstrated for the periodically trapped and coherently driven cold 87Rb atoms,where radiation damping might be much larger than that anticipated in previous proposals and become comparable with radiation pressure.Such an enhancement could be observed even at speeds of only a few meters per second with less than 1.0%absorption,making radiation damping experimentally accessible.
文摘Thaditional implementation of sequential consistency in shared-memory systems requires memory accesses to be globally performed in program order. Based on an event ordering model for correct executions in shared-memory systems, this paper proposes and proves that out-of-order execution does not influence the correctness of an execution providing certain condition is met. Simulation results show that out-of-order execution proposed in this paper is an effective way to improve the performance of a sequentially consistent shared-memory system.
