Phase diagram of Ag–Pd bimetallic nanoclusters by molecular dynamics simulations: solid-to-liquid transition and size-dependent behavior

Abstract

This report on the solid-to-liquid transition region of an Ag-Pd bimetallic nanocluster is based on a constant energy microcanonical ensemble molecular dynamics simulation combined with a collision method. By varying the size and composition of an Ag-Pd bimetallic cluster, we obtained a complete solid-solution type of binary phase diagram of the Ag-Pd system. Irrespective of the size and composition of the cluster, the melting temperature of Ag-Pd bimetallic clusters is lower than that of the bulk state and rises as the cluster size and the Pd composition increase. Additionally, the slope of the phase boundaries (even though not exactly linear) is lowered when the cluster size is reduced on account of the complex relations of the surface tension, the bulk melting temperature, and the heat of fusion. The melting of the cluster initially starts at the surface layer. The initiation and propagation of a five-fold icosahedron symmetry is related to the sequential melting of the cluster.

A molecular dynamics study of cooling rate during solidification of metal nanoparticles

“…In addition to experiments over many years [1,[8][9][10][11], numerical simulations such as molecular dynamics (MD) and Monte Carlo (MC) simulations have contributed to interpreting the configuration and thermodynamic properties of nanoparticles. These atomic simulations have revealed interesting properties unique to nanoparticles such as a stable structure for small particles with a specific magic number [12,13], depression of the melting point [14][15][16][17][18][19][20][21], the effect of substrates on the phase stability of nanoparticles [17,18,20,[22][23][24][25], and the effect of orientation of the substrate on nanoparticle epitaxy [24][25][26][27], the solid-to-liquid transition region of binary nanoparticles [28][29][30][31] and the structural properties of binary nanoparticles [32].…”

Simultaneous melting of shell and core atoms, a molecular dynamics study of lithium–copper nanoalloys

“…Despite decades of study, melting of nanoparticles continues to generate interest among researchers (Andrievski 2014). Many studies have investigated the effect of melting on the size and composition of nanoalloys (Chen et al 2007;Wen et al 2012;Buffat and Borel 1976;Kim et al 2009)). The melting temperature of spherical nanoparticles decreases in proportion to the ratio of the surface area to the volume of the particle (Buffat and Borel (1976)).…”

“…Studies on several bimetallic nanoparticles found that core-shell nanoparticles exhibit two-stage melting: surface melting of the external atoms, followed by homogeneous melting of the core (Mejía-Rosales et al 2006;Yang et al 2008;Huang et al 2013;Sankaranarayanan et al 2005). Melting of nanoalloys originates from the surface and then gradually propagates into the interior region, ultimately resulting in a complete first-order transition from the solid to the liquid phase (Mottet 2013;Wen et al 2012;Yang et al 2008;Huang et al 2013;Kuntová et al 2008;Kim et al 2009). …”

Temperature-dependent properties of 147- and 309-atom iron-gold nanoclusters

“…These novel properties have also triggered theoretical evaluation of the stability and structural evolution of the nanoparticles as a function of temperature. [11][12][13][14] The unusual properties of gold nanoparticles [3][4][5] have prompted experimental and theoretical investigations aimed at discovering novel properties when Au alloys with other transition metals. 15 An interesting combination is that of Au and Fe, which although immiscible in the bulk, forms Au-Fe layered films whose properties (magnetic anisotropy, enhanced Curie temperature, intense interband absorption peak, structure dependent absorption characteristics, etc.)…”