Abstract
Structure and stability of nanometer-sized Ag887, Au887 and Ti787 clusters soft-landed on graphite (at deposition energies Edep = 0.001 − 5.0 eV per atom) are studied by means of molecular dynamics simulations. Parameters for the cluster–surface interactions are derived from complementary ab initio calculations. The shape and the contact angle of deposited clusters are systematically analyzed for different deposition energies and temperature regimes. The Ag887 cluster deposited at Edep ≲ 0.1 eV/atom undergoes collision-induced plastic deformation, thus acquiring an ellipsoidal shape with the contact angle close to 180°. In contrast, Au887 and Ti787 clusters undergo a collision-induced melting phase transition followed by their recrystallization; these processes lead to the formation of the droplet-like shapes of the clusters in a form of truncated spheroids. At larger deposition energies all clusters flatten over the surface and eventually disintegrate at Edep ≈ 0.75 − 1.0 eV/atom (for Ag887 and Au887) and ≈3 eV/atom (for Ti787). It is found also that the shape of deposited clusters is strongly influenced by the strength of cluster–substrate interaction and the corresponding interaction mechanism, namely the weak van der Waals interaction between metal and carbon atoms or the van der Waals interaction with an onset of covalent bonding. Similar phenomena should arise in the deposition of clusters made of other elements, which interact with a substrate by one of the above-described mechanisms.Graphical abstract
Highlights
The interaction of atomic clusters and nanoparticles with surfaces has been a widely studied topic in cluster science over the past several decades [1,2,3]
The dynamics of metal clusters and carbon fullerenes deposited onto different surfaces was explored both experimentally [4,5,6,7] and computationally by means of molecular dynamics (MD) simulations [8,9,10]
A large increase of the internal energy of Au887 and Ti787 clusters deposited at Edep 0.1 eV/atom leads to fast melting and recrystallization of the clusters, which happen over several tens of picoseconds
Summary
The interaction of atomic clusters and nanoparticles with surfaces has been a widely studied topic in cluster science over the past several decades [1,2,3]. The shape, contact angle, contact radius and height of the deposited clusters are systematically analyzed for different deposition energies Edep and temperature regimes. The dependence of these parameters on the initial structure and internal energy of the clusters is elaborated. A large increase of the internal energy of Au887 and Ti787 clusters deposited at Edep 0.1 eV/atom leads to fast melting and recrystallization of the clusters, which happen over several tens of picoseconds These processes lead to the formation of the droplet-like shapes of the clusters in a form of truncated spheroids. We expect that similar phenomena shall arise in the deposition of metal clusters made of other elements (e.g., Pt, Co, Ni, Pd), which interact with a substrate by one of the above-described mechanisms
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