Research interests of Dr. Astrid S. de Wijn

Theoretical physics: statistical physics, condensed matter, and nonlinear dynamics

The common denominator of my work is the investigation of transport of matter, energy, and momentum, and its relationship to microscopic nonlinear dynamics. My aim is to develop new, general, theoretical models for systems which are out of equilibrium or in which equilibrium does not exist. Currently, I focus on two types of systems:
  1. molecules and nanoscale objects on surfaces and
  2. gases and liquids of various levels of complexity.
My studies utilise analytical as well as computational methods to solve fundamental and applied problems.

Nonlinear dynamics of nanosystems

Nanoscale systems are becoming more and more experimentally accessible, due to advances in microscopic manipulation and measurement techniques. Theoretical approaches to experimental results in these systems, however, have often been limit ed to numerical simulations. Because fluctuations are large, the powerful formalism of equilibrium statistical mechanics cannot be applied directly. Additionally, surface effects dominate bulk effects, and interactions are often strongly nonlinear. The most promising basis for understanding the mechanics of nanosystems, therefore, are dynamical systems theory, which also forms the foundations of statistical mechanics, and computer simulations. My goal is to employ the analytical methods of nonlinear dynamics as well as numerical simulations, to study the internal degrees of freedom (vibrations, rotations, etc.) of molecules and nanoclusters, as well as their prominent role in the transport of such objects on surfaces. Deeper understanding of this role provides insight into experimental results and ways to control the motion of nanosystems on surfaces, and contributes important understanding to the development of a statistical formalism for small systems.

Applied kinetic theory

Accurate transport coefficients such as viscosity of complex liquids and gases are needed in many practical applications. Kinetic theory is the only instrument at our disposal for turning detailed knowledge of the interactions between molecules into predictions for transport coefficients. Nevertheless, it is notoriously difficult to obtain accurate results for transport coefficients of any but the simplest systems. My objective is to develop new kinetic approaches to transport coefficients such as viscosity and diffusion of liquids and gases. These approaches are necessarily semi-empirical, making use of existing experimental data on transport coefficients, and combining these with detailed understanding of the mathematics of kinetic theory.