Molecular dynamics simulations of coherent structures in strongly coupled Yukawa liquids

Abstract

This thesis presents a computational study of large scale hydrodynamic flows in strongly coupled liquids using ?first principles? classical molecular dynamics (MD) simulations. The prototype model used in the study is a Yukawa liquid. As is well known, Yukawa liquids are ubiquitous in nature and well known examples include complex or ?dusty? plasmas, colloids and certain astrophysical systems such as giant planetary interiors and cometary tails, to mention a few. The components of a typical Yukawa liquid such as a complex plasma are electrons, positive ions, neutrals and negatively charged dust grains. Such a complex plasma can exist in a state of strong coupling where the ratio of average interparticle potential energy per dust grain can significantly exceed the average kinetic energy. It is important to note that the mutual influence of the components determines the physical state of the system, for eg. the grain-plasma interaction can lead to the charge on a given dust grain to be a function of time i.e Q = Q(t). Hence, a complex plasma cannot, in general, be described by thermodynamic potentials and are as such thermodynamically open systems. As can be expected, an ideal description of complex plasma amounts to modeling grain-grain interactions including the dynamics of electrons, ions and neutrals. Such a description is clearly a formidable challenge even with the availability of modern day computers. One can, however, construct a near ideal ?exact? description of complex plasma by considering only one charged species, namely the dust grains and assuming that both the grain charge and the background plasma do not evolve in time. This allows the grain dynamics to be modeled by a screened Coulomb or a Yukawa potential U(r) = (1/r)exp(and#8722;r/and#955;D), where and#955;D is the Debye length of the background plasma. The resulting N body problem is numerically solved using a classical MD simulation. Using ?first principles? classical MD simulations, the present thesis reports the onset, growth and nonlinear saturation of large scal