Estimating Ag-Cu Nanoalloy Applicability for PCM Data Recording

2020 ◽  
Vol 310 ◽  
pp. 47-52
Author(s):  
Yuri Ya Gafner ◽  
Svetlana L. Gafner ◽  
Daria A. Ryzhkova
Keyword(s):  
Copper Content ◽  
Removal Rate ◽  
Tight Binding ◽  
Heat Removal ◽  
Binding Potential ◽  
Chemical Compositions ◽  
Internal Structures ◽  
Individual Particles ◽  
Dynamics Method ◽  
Change Memory

The paper studies applicability of individual particles of Ag-Cu nanoalloys as data bits in the next generation memory devices constructed on the phase change memory principle. To fulfill this task, the structure formation was simulated with the molecular dynamics method on cooling from the melt of Ag-Cu nanoparticles of the diameter of 2.0 – 8.0 nm of different chemical compositions (with copper content in the alloy from 10 to 50 percent), based on the modified tight-binding potential (TB-SMA). The authors investigated the influence of the size effects and the heat removal rate on the formation of the clusters structure. The investigation showed that different internal structures can be developed upon cooling from the liquid phase, so there were determined some criteria of their stability. Clusters with copper content of not more than 10% and diameters of more than 6.0 nm were isolated from the entire set of the considered particles.

scholarly journals SIMULATION OF THE FRACTAL METAL FILMS FORMATION

2020 ◽  
pp. 424-437
Author(s):  
Дмитрий Викторович Иванов ◽  
Сергей Александрович Васильев ◽  
Николай Юрьевич Сдобняков ◽  
Елена Владимировна Романовская ◽  
Виталий Александрович Анофриев ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Beam ◽  
Gold Film ◽  
Tight Binding ◽  
Copper Surface ◽  
Metal Films ◽  
Binding Potential ◽  
Fractal Structures ◽  
Software Product ◽  
Dynamics Method

В данной работе методом молекулярной динамики с использованием потенциала сильной связи проведено моделирование процесса молекулярно-лучевой эпитаксии с целью определения закономерностей при формировании фрактальных металлических пленок на твердой поверхности. В качестве подложки использовалась медь, пленка формировалась из атомов золота. Показана возможность формирования фрактальных структур в островковой пленке золота на поверхности меди. Различными аналитическими методами с использованием программного продукта Gwyddion проанализирован диапазон изменения фрактальной размерности при различных условиях молекулярно-динамического эксперимента. In this work, molecular dynamics method and the tight binding potential was used to simulate the process of the molecular beam epitaxy in order to determine regularities in the formation of fractal metal films on a solid surface. Copper was used as a substrate, the film was formed from gold atoms. The possibility of formation of fractal structures in an island gold film on the copper surface is shown. Various analytical methods using the Gwyddion software product have used to analyze a range of changes in the fractal dimension under different conditions of molecular dynamics experiment.

scholarly journals STRUCTURAL STABILITY OF Ag AND Ag NANOCLUSTERS WITH A CHANGE IN THE INITIAL MORPHOLOGY

2021 ◽  
pp. 604-611
Author(s):  
Дарья Антоновна Рыжкова ◽  
Светлана Леонидовна Гафнер ◽  
Юрий Яковлевич Гафнер
Keyword(s):  
Tight Binding ◽  
Thermal Relaxation ◽  
Silver Nanoclusters ◽  
Binding Potential ◽  
Magic Numbers ◽  
Structural Transitions ◽  
Thermally Induced ◽  
Second Moment ◽  
Moment Approximation ◽  
Dynamics Method

В статье методом молекулярной динамики с использованием модифицированного потенциала сильной связи TB-SMA (second moment approximation of tight-binding) проводится сравнительный анализ характера термически индуцированных структурных переходов в нанокластерах серебра, число атомов в которых соответствует «магическим» числам икосаэдрической структуры, при вариации их начальной морфологии. Показано, что в случае начальной ГЦК конфигурации формирование Ih модификации происходит либо на этапе предварительной термической релаксации, либо в ходе дальнейшего нагрева. При начальной аморфной морфологии характер структурных переходов претерпевает значительные изменения. Так, например, формирующаяся Ih модификация обладает большей стабильностью в области высоких температур и точка плавления нанокластеров смещается на величину более 100 К. Такой эффект обусловлен более плавным изменением удельной потенциальной энергии нанокластера в сравнении со случаем, когда устойчивая Ih конфигурация формируется при низких температурах. Полученные данные могут быть использованы при процессах создания нанокластеров серебра с требуемым внутренним строением. This article provides a comparative analysis of thermally induced structural transitions in silver nanoclusters with a change in their initial morphology. The study was executed by the molecular dynamics method using the modified TB-SMA (second moment approximation of tight-binding) tight binding potential. The number of atoms in nanoclusters corresponds to the icosahedral structure «magic» numbers. It is shown that for nanoclusters with the initial FCC configuration, the Ih modification is formed either at the stage of preliminary thermal relaxation or during further heating. For nanoclusters with an initial amorphous morphology, the nature of structural transitions undergoes significant changes. For example, the formed Ih modification is more stable at high temperatures and the melting point of nanoclusters shifts by more than 100 K. This effect is due to a smoother change in the specific potential energy of the nanocluster in comparison with the case when a stable Ih configuration is formed at low temperatures. The data obtained can be used in processes to create silver nanoclusters with the required internal structure.

scholarly journals Оценка влияния икосаэдрических "магических" чисел на термическую стабильность малых нанокластеров серебра

2022 ◽  
Vol 64 (3) ◽  
pp. 313
Author(s):  
Д.А. Рыжкова ◽  
С.Л. Гафнер ◽  
Ю.Я. Гафнер
Keyword(s):  
Tight Binding ◽  
Thermal Relaxation ◽  
Silver Nanoclusters ◽  
Binding Potential ◽  
Magic Numbers ◽  
Structural Transitions ◽  
Icosahedral Structure ◽  
Thermally Induced ◽  
Fcc Phase ◽  
Dynamics Method

A comparative analysis of thermally induced structural transitions in silver nanoclusters, the number of atoms of which corresponded to the “magic” numbers of the icosahedral (Ih) structure with variation of their initial morphology, was carried out by the molecular dynamics method using the modified tight-binding potential TB-SMA. It is shown that, in the case of the initial fcc phase, the formation of the Ih modification, depending on the particle size, occurred either at the stage of preliminary thermal relaxation or during further heating. At the initial amorphous morphology, the nature of the structural transitions underwent significant changes. Thus, even in the case of Ag55 clusters, the icosahedral structure was formed only in 50-60% of the experiments performed. Based on the data obtained, it was concluded that to create a stable Ih structure, it is necessary to use the thermal cycling procedure.

scholarly journals SOME NEW RESULTS OF MODELING THE PROCESSES OF THE GAS-PHASE SYNTHESIS OF CU - AU NANOPARTICLES

2020 ◽  
pp. 384-393
Author(s):  
Юрий Яковлевич Гафнер ◽  
Светлана Леонидовна Гафнер ◽  
Юлия Андреевна Куликова
Keyword(s):  
Chemical Composition ◽  
Tight Binding ◽  
Binding Potential ◽  
Particle Structure ◽  
Size Mismatch ◽  
Phase Synthesis ◽  
Small Clusters ◽  
Gas Medium ◽  
Content Of Gold ◽  
Dynamics Method

Методом молекулярной динамики на основе потенциала сильной связи проведена имитация процесса синтеза из высокотемпературной газовой среды бинарных нанокластеров Cu - Au методом конденсации. В качестве начальной конфигурации были использованы 91124 атомов Cu и Au , расположенных хаотично в пространстве с целевым химическим составом CuAu, CuAu, CuAu и CuAu. Найдено, что в случаях стехиометрического химического состава исходной газовой смеси (CuAu или CuAu) наблюдается выделение очень мелких кластеров с подавляющим содержанием в них атомов золота. Также было показано, что многие полученные при таком синтезе наночастицы обладали пятичастичным строением. Сделано предположение, что причиной такого расположения атомов в исследуемых соединениях может быть разный размер атомов золота и меди, приводящий к «разрыхлению» кристаллической решетки. Simulation of synthesis of binary Cu - Au nanoclusters from a high-temperature gas medium by the condensation method was carried out by the molecular dynamics method based on the tight-binding potential. The initial configuration consisted of 91124 Cu and Au atoms was located randomly in space with the target chemical composition CuAu, CuAu, CuAu and CuAu. It was found that in the cases of the stoichiometric chemical composition of the initial gas mixture (CuAu or CuAu), very small clusters with an overwhelming content of gold atoms were observed. It was also shown that many nanoparticles obtained by this synthesis had a five-particle structure. It is assumed that the reason for such an arrangement of atoms in the compounds under study may be the size mismatch of gold and copper atoms, leading to «loosening» of the crystal lattice.

scholarly journals Solidification Enhancement in a Multi-Tube Latent Heat Storage System for Efficient and Economical Production: Effect of Number, Position and Temperature of the Tubes

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3211
Author(s):  
Min Li ◽  
Jasim M. Mahdi ◽  
Hayder I. Mohammed ◽  
Dmitry Olegovich Bokov ◽  
Mustafa Z. Mahmoud ◽  
...  
Keyword(s):  
Free Convection ◽  
Heat Storage ◽  
Liquid Fraction ◽  
Removal Rate ◽  
Heat Removal ◽  
Vertical Direction ◽  
Heat Transfer Fluid ◽  
Latent Heat Storage ◽  
Solidification Mode ◽  
The Impact

Thermal energy storage is an important component in energy units to decrease the gap between energy supply and demand. Free convection and the locations of the tubes carrying the heat-transfer fluid (HTF) have a significant influence on both the energy discharging potential and the buoyancy effect during the solidification mode. In the present study, the impact of the tube position was examined during the discharging process. Liquid-fraction evolution and energy removal rate with thermo-fluid contour profiles were used to examine the performance of the unit. Heat exchanger tubes are proposed with different numbers and positions in the unit for various cases including uniform and non-uniform tubes distribution. The results show that moving the HTF tubes to medium positions along the vertical direction is relatively better for enhancing the solidification of PCM with multiple HTF tubes. Repositioning of the HTF tubes on the left side of the unit can slightly improve the heat removal rate by about 0.2 in the case of p5-u-1 and decreases by 1.6% in the case of p5-u-2. It was found also that increasing the distance between the tubes in the vertical direction has a detrimental effect on the PCM solidification mode. Replacing the HTF tubes on the left side of the unit negatively reduces the heat removal rate by about 1.2 and 4.4%, respectively. Further, decreasing the HTF temperature from 15 °C to 10 and 5 °C can increase the heat removal rate by around 7 and 16%, respectively. This paper indicates that the specific concern to the HTF tube arrangement should be made to improve the discharging process attending free convection impact in phase change heat storage.

scholarly journals Structure Simulation of Nickel Clusters by Transferable Tight－Binding Potential

2000 ◽  
Vol 49 (1) ◽  
pp. 54
Author(s):  
Luo Cheng－lin ◽  
Zhou Yan－huai ◽  
Zhang Yi
Keyword(s):  
Tight Binding ◽  
Binding Potential ◽  
Nickel Clusters ◽  
Structure Simulation

The Impact of Manufacturing Technology on the Thermal and Electrical Properties of Ceramic Powders Intended for Spraying Using the APS Method

2011 ◽  
Vol 465 ◽  
pp. 219-222 ◽  
Author(s):  
Grzegorz Moskal ◽  
Andrzej Grabowski
Keyword(s):  
Thermal Diffusivity ◽  
Spray Drying ◽  
Internal Structures ◽  
Spherical Structures ◽  
Thermal And Electrical Properties ◽  
Chemical And Phase Compositions ◽  
Surface Morphologies ◽  
The Impact ◽  
Spraying Method ◽  
Individual Particles

This article describes the microstructures, chemical and phase compositions, surface morphologies, and internal structures of three ZrO2 x 8Y2O3-type of powders obtained by different manufacturing methods. The first of the analyzed powders was a conventionally prepared form of the material obtained by the spraying method. The second powder was a spherically shaped form of the material obtained from the spray drying process. It displayed a distinctive surface morphology characterized by a rough structure with visible cavities. The particle sizes of these two powders were comparable. The third form of the powder was classified as “nano” and was obtained by a grinding and crushing method. The shapes of individual particles were generally polyhedral with smooth surfaces and no visible porosity. A study of the chemical composition of each form of the powder did not show significant differences, similar to the results obtained from the phase composition study. The results of thermal diffusivity and electrical impedance studies indicated that the electrical and thermal properties of the powders with spherical structures, i.e., sprayed and spray drying, were very similar. The thermal diffusivity and impedance properties of these two powders were greater than those of the ground powder with a finer grain size.

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