Impact dynamics of molecular clusters on surfaces: Fragmentation patterns and anisotropic effects

Abstract

The fragmentation dynamics of (H2O)1032 clusters colliding with a repulsive surface at incident velocities of 1753 m/s and 2909 m/s, corresponding to kinetic energies of 0.5 and 1.5 times the cluster binding energy, has been examined in a classical molecular dynamics simulations study. The results show a large anisotropy in the energy redistribution inside the cluster upon impact, which leads to asymmetric fragmentation, starting in the leading part of the cluster. The low-mass region of the fragment size distribution can be described by a power law with an exponent close to −1.6, and the range of this region increases with increasing incident velocity. The formed fragments have rather uniform internal temperatures close to the standard boiling point of water, but the translational energy of the monomers formed upon collision is much larger, pointing at the asymmetric energy distribution inside the cluster. The angular distributions of fragment mass and fragment kinetic energy peak at grazing exit angles. For the investigated conditions, the dynamics is insensitive to the details of the initial structure of the cluster.

Simulation of cohesive head-on collisions of thermally activated nanoclusters

“…There are a lot of studies on cluster-cluster and clustersurface collisions based on the molecular dynamics simulation. [27,28,29,30,31] We observe variety of rebound processes in such systems caused by the competition between the attractive interaction and the repulsive interaction of two colliding bodies. Binary collisions of identical clusters cause coalescence, scattering, and fragmentation depending on the cluster size and the impact energy.…”

Origin of rebounds with a restitution coefficient larger than unity in nanocluster collisions

“…There are many numerical studies on cluster-cluster and clustersurface collisions based on the molecular dynamics simulation. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] We observe variety of rebound processes for such systems caused by the competition between the attractive interaction and the repulsive interaction of two colliding bodies. Binary collisions of identical clusters cause coalescence, scattering, and fragmentation depending on the cluster size and the impact energy.…”

Molecular dynamics simulations of the micro-solvation of ions and molecules during cluster–surface collisions

“…We employ an SPC-based [17], rigid water model that previously has been used for MD simulations of H 2 O cluster-surface impact [15,[18][19][20]. The Na þ ion interacts with its charge of 1e electrostatically with the point charges of 0.41e and )0.82e located at the positions of the hydrogen and oxygen atoms in the SPCwater, respectively.…”

“…This cluster was equilibrated at an internal temperature of 47 K, as described in [15]. A Na þ doped cluster was generated by introducing an ion to the center of the neat water cluster, whereafter the system was allowed to equilibrate and relax at a temperature of 47 K. At time t ¼ 0, the cluster was placed above the surface, outside the range of the H 2 O-surface interaction potential and was given a velocity in the direction normal to the surface plane.…”

“…While the impact-induced injection of energy into the initially cold molecular cluster as well as the resulting charged and neutral cluster fragment size distributions have been studied in detail experimentally [11][12][13] as well as by molecular dynamics (MD) simulations [14,15], less attention has been attributed to the fate of the near-order in an impact heated cluster [15,16]. Here, we use classical MD simulations to monitor exchange process in the solvation shell of ions inside an impact heated cluster.…”