Icosahedral metallic nanoclusters: low-temperature structures or pre-melting ones?

Melting of cuboctahedral nanoclusters of fcc metals ( Ag , Au , Cu , Ni , Pd и Pt ) containing 561 atoms and a transition to icosahedral isomers preceding their melting were simulated using the isothermal molecular dynamics. The heating process was simulated in the NVT ensemble using the well-known open LAMMPS program, the Verlet velocity algorithm and the Nosé-Hoover thermostat. The interatomic interactions in metal nanoparticles were reproduced by employing the embedded atom method. At a relatively low for MD experiments heating rate of 0,15 K/ps, the cuboctahedron → icosahedron transition was observed in the face-centered cubic nanoparticles of all the above metals, except for Ag nanoparticles. However, an increase in the heating rate to 1,5 K/ps led to the fact that the cuboctahedron → icosahedron transition began to be observed in Ag nanoclusters as well. Unlike nanoparticles of other metals, the cuboctahedron → icosahedron transition in Pt nanoclusters occurs at a very low temperature, close to the initial temperature preceding the heating of the particles and equal to 10 K. In contrast, in Ni particles the cuboctahedron → icosahedron transition was observed at a temperature close to the melting point.

metal nanoclusters, isomers, cuboctahedron-icosahedron transition, melting, molecular dynamics