Dual structural transition in small nanoparticles of Cu-Au alloy

Gafner, Yu. Ya.; Гафнер, С. Л.; Redel, L. V.; Zamulin, I. S.

doi:10.1007/s11051-018-4161-2

Cited by 12 publications

(18 citation statements)

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“…Также большое значение имеет следующий факт, установленный нами в [22] по результатам компьютерного моделирования. В [22] было выяснено, что в ходе нагрева нанокластеров Cu 3 Au происходят типичные изменения в его структуре, в результате которых атомы золота начинают постепенно вырываться из узлов кристаллической решетки L1 2 и занимать более выгодные с энергетической точки зрения (при данной температуре) позиции, что носит название перехода «порядок-беспорядок». То есть, если макроскопический образец Cu 3 Au равновесно нагревать, то при температуре ниже 663 К сплав имеет L1 2 построение атомов.…”

Section: результаты и обсуждениеunclassified

“…При дальнейшем нагреве неупорядоченная ГЦК фаза остается в равновесии до тех пор, пока не достигнет температуры плавления. Однако в [22] было показано, что с дальнейшим ростом температуры первоначально однородный химический состав наночастиц Cu-Au начинает изменяться вследствие процесса вытеснения атомов Au в поверхностной слой, причем скорость процесса сегрегации увеличивается с температурой, что подтверждается экспериментально [23]. Поэтому можно заключить, что процессы атомного перемешивания и разделения определяются многими факторами.…”

Section: результаты и обсуждениеunclassified

“…Как уже говорилось выше, энергия связи медных атомов при малых размерах наночастиц оказывается больше чем у атомов золота. Данная тенденция наблюдалась нами для частиц наносплава Cu-Au, содержащих более N > 400атомов, из-за чего увеличение концентрации внедренных атомов Au в нанокластере Cu приводило к линейному уменьшению температуры плавления наносплава [22]. Поэтому при имеющейся в модельной системе температуре кластер Cu-Au фактически будет представлять собой частицу с медным центром и поверхностью обогащенной атомами золота (Рис.…”

Section: результаты и обсуждениеunclassified

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Analysis of the size distribution of binary Cu-Au nanoparticles during synthesis from a gaseous medium

2020

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The paper presents the results of molecular dynamics computer simulation studies on the synthesis of binary Cu-Au nanoclusters by condensation from the gaseous phase. To calculate the interatomic interaction forces, the modified TB-SMA potential with a fixed cutoff radius was used. As the initial structure, a configuration containing a total of 91 124 Cu and Au atoms distributed in a cubic lattice with a parameter of 30 • а В , where а В is the Bohr radius, was chosen and periodic boundary conditions were used. For the analysis, we selected the initial configurations of different chemical composition Cu 3 Au, Cu-Au, Cu 90 Au 10 , Cu 60 Au 40 , which were cooled in the condensation process to 77 K. As a result of numerical experiments, condensation of liquid droplets from hot high-density gas was observed, which then crystallized into primary particles of nanometer size and then merged into larger formations. According to the simulation results, a relationship was found between the number of clusters formed at the first stage of synthesis and the percentage of gold atoms in the primary gaseous medium. It was concluded that this fact was a consequence of different binding energies between copper and gold atoms, which led to different melting points of these clusters. Despite the random nature of further agglomeration processes, this trend still persists at lower temperatures. Therefore, using different concentrations of copper and gold atoms, it is possible, in principle, to control the formation of Cu-Au binary clusters from the gas phase with some predetermined chemical composition and size.

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Section: результаты и обсуждениеunclassified

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Analysis of the size distribution of binary Cu-Au nanoparticles during synthesis from a gaseous medium

2020

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“…Thus, in heterogeneous catalysis, it has been shown that Cu-Au nanoalloys usually exhibit a synergistic effect in oxidative reactions and the selective oxidation of carbon monoxide (CO) to carbon dioxide at ambient temperature as well as in the selective oxidation of benzyl alcohol to benzaldehyde and in the epoxidation of propene with nitrous oxide. Moreover, in experimental and theoretical works [9], it was clearly shown that the partial substitution of copper with gold in many cases shows a change in the physicochemical properties, for example, there is an increase in catalytic activity when compared to the monometallic Au or Cu nanoparticles [3]. In addition to catalysis, Cu-Au nanoalloys are also of great interest in optics, where it was found that the doping of copper into gold nanoparticles causes the appearance of strong surface plasmon resonances, with the energy and resonance line width depending on the percentage of copper.…”

Section: Introductionmentioning

confidence: 99%

The role of gold atom concentration in the processes of formation of Cu-Au nanoparticles from the gas phase

Gafner¹,

Гафнер²,

Ryzkova³

et al. 2020

Preprint

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Currently, bimetallic nanoparticles have been widely used in various fields of nanotechnology, but the main area of their application continues to be the catalysis of chemical reactions. However, it soon became clear that the catalytic activity of nanoalloys very much depends on their size, chemical composition, and shape. Therefore, the question of controlling the synthesis of bimetallic nanoparticles to obtain particles of the desired size, spatial structure, and chemical composition is very acute. In the synthesis of the Cu-Au studied by us, nanoparticles can occur either through chemical or physical methods, each of which has its own drawbacks. Though it is very difficult to achieve the required target chemical composition of nanoparticles during chemical synthesis, their size can be stabilized quite well. In turn, physical synthesis methods mainly allow you to withstand the required chemical composition, but the size of the resulting particles varies significantly. To solve this contradiction, we studied the formation of Cu-Au nanoparticles of different chemical compositions from a gaseous medium using computer Molecular Dynamics simulation to determine the effect of the concentration of gold atoms on the size and actual chemical composition of the formed bimetallic nanoparticles.

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“…Thus, in the derivation of semiempirical interatomic potential parameters within the tightbinding based second-moment approximation (TB-SMA), and in embedded-atom methods (EAM, MAEAM), experimentally derived E coh were mostly used [4,5], while some other studies employed density functional theory (DFT) computed values [6]. More recent examples comprise modeling of compositional configuration in binary [7][8][9][10] and ternary [11] TM alloy NPs, including surface segregation phenomena and structural transitions [10]. A more direct involvement of E coh in modeling of NPs appeared in the framework of the bond-order-simulation approach [12].…”

Section: Introductionmentioning

confidence: 99%

Thermal properties and segregation phenomena in transition metals and alloys: modeling based on modified cohesive-energies

Polak

Rubinovich²

2019

J. Phys.: Condens. Matter

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In spite of free-atom electronic-relaxation contributions to transition-metal cohesive-energies, numerous studies have misused the latter instead of using the solid-state interatomic bondenergy in modeling bulk and surface properties. This work reveals that eliminating the free-atom contributions from experimental cohesive-energies leads to highly accurate linear correlations of the resultant bond-energies with melting temperatures and enthalpies, as well as with inverse thermal-expansion coefficients, specifically for the fcc transition-metals. Likewise, predictions of surface segregation phenomena in Cu-Pd and Au-Pd alloys on the basis of the modified energetics are in much better agreement with reported low-energy ion scattering spectroscopy (LEISS) experimental results, as compared to the use of cohesiveenergy values. A last demonstration of the problem and its solution involves the significant impact of the modification on segregation (separation) phase transitions in Cu-Ni model nanoparticles.

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Dual structural transition in small nanoparticles of Cu-Au alloy

Cited by 12 publications

References 38 publications

Analysis of the size distribution of binary Cu-Au nanoparticles during synthesis from a gaseous medium

Analysis of the size distribution of binary Cu-Au nanoparticles during synthesis from a gaseous medium

The role of gold atom concentration in the processes of formation of Cu-Au nanoparticles from the gas phase

Thermal properties and segregation phenomena in transition metals and alloys: modeling based on modified cohesive-energies

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