3 years ago

Size-dependent melting modes and behaviours of Ag nanoparticles: a molecular dynamics study.

Wu, Zhou, Shi, Liang
The size-dependent melting behaviours and mechanism of Ag nanoparticles (NPs) with diameters of 3.5-16 nm were investigated by molecular dynamics (MD). Two distinct melting modes, non-premelting and premelting with transition range of about 7-8 nm, for Ag NPs were demonstrated via the evolution of distribution and transition of atomic physical states during annealing. The small Ag NPs (3.5-7 nm) melt abruptly without stable liquid shell before melting point, which is characterized as non-premelting. A solid-solid crystal transformation is conducted through the migration of adatoms on surface of Ag NPs with diameters of 3.5-6 nm before initial melting, which is mainly responsible for increasing slightly melting point of Ag NPs. On the other hand, surface prmelting of Ag NPs with diameters of 8-16 nm propagate from outer shell to inner core with initial anisotropy and late isotropy as temperature increases, and the close-packed facets {111} melt by a side-consumed way which is responsible for facets {111} melting in advance relative to crystallographic plane {111}. Once a stable liquid shell is formed, its size-independent minimum thickness is obtained, and a three-layer structure of atomic physical states is set up. Last, the theory of point defect-pair (vacancy-interstitial) severing as the mechanism of formation and movement of solid-liquid interface was also confirmed. Our study provide a basic understanding and theoretical guidance for research, production and application of Ag NPs.

Publisher URL: http://doi.org/10.1088/1361-6528/aa92ac

DOI: 10.1088/1361-6528/aa92ac

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