1999/11/18 by Andrés Aguado, Andres Aguado, Aguado, Andres +8
Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #Advanced Chemical Physics Studies #Material Dynamics and Properties #cond-mat #nanoparticles nucleation surface interactions #physics.atm-clus
paper · pdf · doi:10.48550/arxiv.physics/9911042
LaTeX file. 7 pages with 9 pictures. In the revised version, the discussion of melting of amorphous clusters is removed, and that of melting of icosahedral clusters is extended
arxiv created 2000/05/06 · arxiv updated 2009/11/30
The melting-like transition in sodium clusters NaN, with N=55, 92, and 142 is studied by using constant-energy molecular dynamics simulations. An orbital-free version of the Car-Parrinello technique is used which scales linearly with system size allowing investigation of the thermal behaviour of large clusters. The ground state isomer of Na142 (an uncomplete three-shell icosahedron) melts in two steps: the first one (at approx. 240 K) is characterized by the high mobility of the atoms located on the cluster surface; the second, homogeneous melting (at approx. 270 K), involves diffusive motion of all the atoms across the cluster. For the case of Na92, the icosahedral structure has a larger number of surface vacancies, and melts in two well separated steps, surface melting at approx. 130 K and homogeneous melting at approx. 240 K. Na55, a complete two-shell icosahedron, melts in a single stage at approx. 190 K. Our results on homogeneous melting for Na142 and Na92 are in excellent agreement with recent experimental determinations of melting temperatures and latent heats. However, the experimentally observed enhancement of the melting temperature around N=55 is not reproduced by the calculations.