The results of comparative atomistic simulation are presented for segregation and thermally induced structural transformations (melting/crystallization) in binary Pt–Pd nanoalloys and ternary Pt–Pd–Ni nanoparticles, where Ni (20 at

The reliability of the atomistic simulation is determined in terms of the correctness of the problem statement, including the choice of the interatomic interaction potential and its parameterization. In this paper, a detailed testing of the tight-binding potential parameters was carried out by means of studying the influence of the ratio between pair and many-body interactions on the process of the structure formation in binary Pd-Pt nanoparticles. Three parameterizations of the tight-binding potential for the cross parameters were selected: set (I) corresponded to the use of the Lorentz-Berthelot rule, sets (II) and (III) specified the scaling laws for the pair interaction parameters and the many-body interaction parameters, respectively. For sets (I) and (III), the surface segregation of palladium atoms was established, while the use of set (II) led to the formation of the Janus structure. In addition, differences in the formation of the local structure in binary Pd-Pt nanoparticles were established. Set (III) predicts the dominance of the local bcc structure. Radial distributions of the local density of Pd and Pt atoms in the Pd-Pt nanoparticles at a final temperature of 300 K were also calculated.

A comparative study combining the experimental technique of scanning electron microscopy and atomistic simulation by (molecular dynamics) was carried out using of the ternary CoCrMo nanoalloy as an example. Employing the technology of selective laser melting based on the PR-KH28M6 powder, a sample was made for which a non-uniform surface composition with respect to the presence of cobalt and chromium was identified, i.e. areas were simultaneously enriched and depleted in these elements, which indicates the possibility of forming various intermetallic compounds based on them. In the process of atomistic simulation, three nanoparticles of the ternary CoCrMo nanoalloy with the number of 10000, 15000 and 30000 atoms were subjected to a sequential cycle of heating and cooling, including the identification of phase transitions corresponding to melting and crystallization, respectively. The corresponding temperatures of the beginning and end of the phase transition were determined. The regularities of structural and surface segregation in the ternary CoCrMo nanoalloy are described. It is noted that for nanoparticles containing 10000 atoms, only a shell of cobalt atoms is formed without forming a core, while for nanoparticles containing 15000 and 30,000 atoms, an onion-like structure is formed. Chromium atoms form either the core of the nanoparticle as at N =10000 or the peripheral region as at N =15000 and 30000. Molybdenum atoms behave indifferently, i.e. are distributed uniformly throughout the entire volume of the nanoparticles under

The article is devoted to the study of stability of ternary Cu-Fe-Ni nanoparticles (consisting of 5400 atoms) with a core-shell structure and its relationship with the surface segregation. The main focus is on modeling their structural formation using the LAMMPS software. The authors test the hypothesis that stability of nanoparticles depends on the spontaneous segregation of one of the components to the surface. Three configurations with different atomic distributions (configuration Cu 45 Fe 45 Ni 10 with random distribution of atoms, as well as configurations - Cu 25 Fe 25 @ Ni 50 and Fe 25 Ni 25 @Cu 50 ) are considered, and numerical modeling is performed for each of them using molecular dynamics methods and applying the tight-binding and embedded atom method potentials. The analysis showed that copper tends to segregate to the surface, while nickel concentrates in the core, significantly affecting mechanical properties of the nanoparticles. Patterns of the defect formation and their impact on the strength of nanostructures were identified. The article emphasizes that the correct choice of shell and core can both stabilize and destabilize the nanoparticles, providing prospects for the practical application of these materials.

In this paper, we study the layer-by-layer growth process of a bimetallic nanoparti-cle Au-Ag having face-centered cubic and decahedron structure. The Monte Carlo method was chosen to implement this problem combined with an approach from molecular dynamics. The Monte Carlo method allows solving of problems with periodic boundary conditions. Computer implementations of the method have been developed in two different software products Metropolis (Tver State University) and Tsuyoyama (Institute of Information and Communication Technol-ogies). Interaction between atoms is calculated using multi-body tight-binding model. It is estab-lished that the order of addition of atoms (simultaneous or layered) affects the chemical ordering in the studied gold-silver equiatomic nanoalloys. In addition, the difference between the values of specific energy corresponding to Metropolis and Tsuyoyama software becomes quite small, supporting the inference that the numerical procedure for the layer-by-layer growth is adequate.

In this work, scenarios of structure formation in ternary nanoparticles based on platinum and palladium of four stoichiometric compositions of different sizes were studied, with nickel acting as a dopant. Two alternative methods were used: the molecular dynamics method (implemented in the open source software LAMMPS) and the Monte Carlo method (implemented in the Metropolis scheme). In addition, to describe the interatomic interaction, two versions of force fields were used: the modified tight-binding potential (when implementing the molecular dynamics and Monte Carlo methods) and the embedded atom potential (when implementing the molecular dynamics method). Based on the results of a series of computer experiments, it was found that palladium atoms have increased segregation to the surface. At a cooling rate of 0,1 K/ps, an ordered crystalline FCC structure with inclusions of the HCP phase is formed. With an increase in the nickel dopant content to 20% in the ternary Pd-Pt-Ni nanoparticle, the identifiable local structure becomes more complex, both in terms of the number of phases and in terms of structural segregation.

In this study, the possibility of controlling the coalescence of clusters during the formation of bimetallic nanoparticles and nanoalloys is demonstrated for the first time using joint electric explosion of Nb/Al and Nb/Ag wires under an argon atmosphere as an example. The evolution of clusters in the condensed phase is considered based on the adiabatic approximation to expand the products of the electric explosion of wires. Controlling the temperature and size of the clusters formed under the electric explosion of wires generating the energy necessary for the transition from the metallic state to the two-phase state (clusters of the condensed phase and weakly ionized plasma) allows synthesizing nanoparticles and bimetallic nanoparticles possessing the structures of nanoalloys and Janus particles, respectively. The experimental studies are supplemented by describing structural patterns and segregation phenomena using a hybrid computer experiment that adopts two alternative methods, i.e., the Monte Carlo and molecular dynamics methods. Both methods predict similar structure formation trends, particularly segregation patterns, in Nb-Ag and Nb-Al nanoparticles. For the first time, we have obtained bimetallic nanoparticles possessing a more complex structure, compared to the formerly known core shell, namely the onion-like structure. The Nb-2964-Ag-2964 and Nb-2964-Al-2964 nanoparticles s are characterized by the formation of icosahedral cores and crystalline cores based on the hcp and fcc phases, respectively, over the entire temperature range studied. (C) 2022 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

В данной работе методом молекулярной динамики с использованием потенциала сильной связи исследовались биметаллические наночастицы Au - Co трёх стехиометрических составов различного размера. Установлены закономерности структурообразования, описаны их характерные особенности. В частности, в составах с 50ат.% и 75ат.% содержанием Au образуются множественные малые ядра локальной икосаэдрической симметрии. Только в составе Co -25ат.% Au с увеличением размера частиц преобладают кристаллические фазы. Выявлены составы, в которых внутренняя симметрия наночастицы определена наличием одного икосаэдра, либо сверхструктуры из нескольких икосаэдров. Рассчитаны концентрационные зависимости энергии смешения биметаллической наночастицы Au - Co. Показано, что в определённом диапазоне размеров существуют концентрационные составы, при которых биметаллический наносплав может проявлять нестабильность. С использованием калорических кривых потенциальной части внутренней энергии определены температуры кристаллизации. Установлено, что температура кристаллизации демонстрирует умеренный, либо существенный, в зависимости от состава, рост с увеличением размера биметаллических наночастиц Au - Co. This work studied bimetallic Au - Co nanoparticles of three stoichiometric compositions of various sizes by the molecular dynamics method using the tight-binding potential. The regularities of structure formation are established, their characteristic features are described. In particular, in compositions with 50at% and 75at% Au content, multiple small nuclei of local icosahedral symmetry are formed. Crystalline phases prevail only in the Co - 25 at% Au composition with an increase in the particle size. Compositions are revealed in which the internal symmetry of a nanoparticle is determined by the presence of one icosahedron or a superstructure of several icosahedrons. The concentration dependences of the mixing energy of a bimetallic Au - Co nanoparticle are calculated. It is shown that there are concentrations of compositions at which bimetallic nanoalloys can exhibit instability in a certain size range. Crystallization temperatures were determined using the caloric curves of the potential part of the internal energy. It was found that the crystallization temperature demonstrates a moderate or significant, depending on the composition as well as growth with an increase in the size of bimetallic Au - Co nanoparticles.