Translation-Rotation Coupling in Collisions of Frictional Spheres and Structural Diversity and Stability in Amorphous Materials

Abstract

There are a number of advantages of using computational simulation methods in chemistry research – the exploration of a conditions and parameters that are not feasible in the laboratory, time saving and cost saving compared to certain experimental methods, and the ability to reveal information that is difficult or impossible to obtain experimentally. The first study (Chapter 2) in this thesis uses molecular dynamics simulation methods developed for granular material, to introduce a model which studies the coupling of translational and rotational velocities of a spherical particle in collision with a surface. Analytical treatments are presented and kinematic expressions are derived for the important limiting classes of two types of collision: energy conserving and rapid transverse dissipation. The second study (Chapter 3) theoretically studies, from the results of Chapter 2, the consequences of the collision between a particle and two parallel walls under a non-slip boundary condition applied at the microscopic level. Results show the deposit of energy from wall to particle preferentially choses the rotational degree of freedom, and the particle can be trapped within a confined space with a bounded oscillation of energy. The third study (Chapter 4) presents a new diversity measure for the structural diversity of crystals and glasses, adapted from biodiversity literature, which shows great effectiveness in the filtering of noise. The Favoured Local Structure (FLS) lattice model is used to produce analytical data. Diversity measures show that the stability of structures involve the inclusion and exclusion of local structures, and the spectrum between crystal and glass is associated with a stabilization of either point-like defects or grain boundaries. A common ground in these distinctive studies is the use of simple models, which proves to be functional and effective for investigating generic problems.