The Sodium Atom Clusters The Collision Dynamics

This thesis reports a study on the collision dynamics of Na clusters by means of distance dependent tight-binding molecular dynamics (DDTB-MD).Cluster is a new form of material state that is between atoms and massive material. The investigation on it can help us to discern some properties of massive material as well as some special laws of microscopic systems. A new method for fabricating new materials with special performances can also be developed by studying the microstructure and special physicochemical properties of clusters.Clusters collision is a new direction in the cluster physics study, which makes it possible to study the dynamics properties of clusters. It is very important to study the collision processes between different clusters for understanding the non-local interaction, the dissipation in variety different motions, the lifetime of the compositions formed inside the collision, the extent of mixing of the degree of freedom, the reaction of selectivity of clusters and the formation of new clusters. As the simplest prototype, the alkali sodium cluster can be directly compared with nucleus. As a result, it has become an intensive cluster system, which experimental and theoretical researchers are interested in. Up to now, a large number of experimental data have been accumulated. However, the main aspects of the studying concern the symmetric collision. In fact, the big clusters and moleculars produced in experiments do not always have the good symmetric properties. So it is more imperative to simulate the non-symmetric collision between the projectile and target clusters.Within the framework of distance dependent tight-binding moleculardynamics (DDTB-MD) the collision dynamics of Nan is studied systematically. The software was improved based on that for symmetric collision so as to be able to study the non-symmetric collision and the collision between two Nan clusters with different temperatures. Different reaction mechanisms have been observed at the different incident energies and different impact parameters, such as fusion reaction, deep inelastic collision (DIG) and quasi-elastic collision, those are similar to the nuclear heavy-ion collisions (HIC). However, different interactions in nuclear system and cluster system give rise to different dynamical properties of them. One example is that the collisions of clusters with different geometric structures with the same cluster will demonstrate different properties. For example, at lower incident energy central collision a geometrically symmetric cluster with the target is feasible to form a more stable and larger cluster. It is very important to know this conclusion for producing new clusters. Also, it was known that the cluster collision process is reversible. At last, it was discovered that there could be rotation in the process at adequate conditions. The maximal rotation energy can reach one fifth of total excitation energy in cluster collisions, which is much less than what in HIC.