Stress distribution and mechanical properties of free and assembledNi3Alnanoclusters

Abstract

Classical molecular dynamics with a semiempirical N-body potential is used to study the distribution of local stress in bimetallic Ni 3 Al nanoparticles and in cluster-assembled materials. The materials considered are synthesized with these particles by low-energy deposition at 0.5 eV per atom and by compaction with an external pressure of 2 GPa, thus featuring different nanostructures. Both are nanoporous, the lowest density being obtained by deposition. Their mechanical response to a uniaxial external load is then studied and deformation mechanisms are identified and are found to be similar in both nanostructures. In the core of isolated clusters, the partial pressures on the nickel and aluminium subsystems are found to differ by several GPa and, as a balance to surface tension, the hydrostatic core pressure is positive and depends on the cluster size. The surface stress is tensile and, because of structural disorder, the partial pressures distributions on Ni and Al at the surface are scattered. When nanostructured systems are formed, strong and highly inhomogeneous shear stress appears, the cluster cores may become tensile, and the interfacial areas remain mainly tensile as well. The partial pressure difference between Ni and Al is somewhat reduced. It is shown that the effect of temperature is to reduce this difference still further and to homogenize the spatial stress distribution. When subjected to a uniaxial stress, both materials display an elastic and a plastic regime. The elastic limit is the lowest for the most porous material and decreases with increasing temperature. Plastic deformation is dominated by both grain boundary sliding and by the enlargement of the open volumes, without evidence for the nucleation of cracks. These open volumes are found to facilitate dislocation activity which is evidenced in grains with sizes as small as two nanometers. This dislocation activity is found to result in the production of stacking faults as well as to the recovery of defects induced by the deposition or by the compaction.

Core–shell-structured bimetallic clusters and nanowires

“…In our study, periodic boundary conditions were applied along the NW axis, but no periodic boundary conditions were used for the cluster. This method has been proved to be successful in the study of bimetallic alloys [44,45], thin films [46], and clusters [27,[47][48][49][50][51][52]. Simulations and our programming details for the study of the structural properties of the bimetallic clusters can be found elsewhere in the literature [47,48,52] and in our previous work [27,[49][50][51].…”

Atomistic Modeling of Multishell Onion-Ring Bimetallic Nanowires and Clusters

“…Semi-grand-canonical ensemble Monte Carlo (SEMI-GCMC) simulations were used to study the structures of bimetallic nanowires and clusters, which is efficient to study the chemical ordering of the bimetallic systems. − Details of this method can be found in our previous work. ,, The total number of atoms ( N = N A + N B , A/B = Pd/Pt, Ag/Au, and Ag/Pd), chemical potential difference (Δμ = μ B − μ A , A/B = Pd/Pt, Ag/Au, and Ag/Pd) between the two species, and temperature T were fixed, but N A and N B (A/B = Pd/Pt, Ag/Au, and Pg/Pd) were allowed to vary in the SEMI-GCMC method. Therefore, the chemical composition and atomic ordering at a given temperature were obtained by performing the MC simulation at a fixed value of chemical potential difference Δμ between the two species in the nanowire and cluster.…”

Моделирование Взаимодействия Двудольных Биметаллических Кластеров С Низкоэнергетическими Кластерами Аргона

“…Было принято во вни-мание, что потенциал Акланда реалистично описывает Физика твердого тела, 2017, том 59, вып. 1 структуру однокомпонентных нанокластеров при раз-личных температурах [41], а также механические свой-ства однокомпонентных и бинарных наночастиц [42,43]. Вычисленные согласно потенциалу Акланда теплоты перемешивания пар Ni−Al H mix {AB} = −18.3 kJ/mol и Cu−Au H mix {AB} = −5.3 kJ/mol качественно соответству-ют приведенным выше экспериментальным значениям, что позволило оценивать влияние взаимного перемеши-вания компонентов кластеров на измеряемые параметры.…”