Controlled Deposition and Glassification of Copper Nanoclusters

The dynamics and energy conversion and redistribution pathways in collisions of nanocrystals with bare solid surfaces and with adsorbed liquid films are investigated with molecular dynamics simulations. While impact of an ordered Cu14, icosahedral cluster on a bare C u ( l l 1 ) surface at velocities larger than thermal leads to various outcomes including implantation, indentation, disordering, and spreading, deposition into a low-density liquid film (argon) results in efficient energy transfer to the liquid which for incidence velocities as high as 2-4 km/s can lead to controlled soft landing of a crystalline cluster on the solid substrate. For an incidence velocity of 2 km/s the cluster does not melt, maintaining its icosahedral structure, while for a velocity of 4 km/s the cluster superheats and melts and subsequently recrystallizes after soft landing on the C u ( l l 1 ) surface. In collisions of the cluster with a higher-density liquid (xenon), with incidence velocities of 2-4 km/s, a larger fraction of the cluster translational energy is converted into internal energy of the cluster than in the case of the argon film. Such collisions lead to rapid attenuation of the cluster incident velocity, accompanied by ultrafast heating to high temperatures, superheating, and melting of the cluster. For certain impact velocities, e.g., 2 km/s into xenon, fast cooling via heat transport into the fluid can quench the metallic cluster into a glassy state. The branching ratios for conversion, partitioning, and dissipation of the incidence translational energy of the projectile cluster into internal degrees of freedom of the cluster and those of the target fluid are determined by the relative mass densities and sound velocities of the two materials. New methods for controlled growth of nanophase materials and for preparation of nanoglass aggregates, based on cluster deposition onto liquids, are suggested.