# Research of the Dellago Group

We study the statistical mechanics of complex systems with the help of computer simulations. In particular, our research is focused on the following areas.

### Dynamics of complex systems

Many processes in areas ranging from physics to chemistry, biology and materials science are all characterized by wide ranges of length, energy, and time scales. A primary research goal in our group is to develop computer simulation algorithms which overcome these difficulties. Recently, Prof. Dellago has helped develop **transition path sampling**, a computer simulation technique to investigate processes involving rare events. Prof. Dellago has recently organized a workshop, where transition path sampling and other techniques to deal with rare events in complex systems were discussed.

### Proton conduction in aqueous media

Proton conduction in aqueous environments is fundamental to many biological and technological processes ranging from ATP synthesis to electrical power generation in hydrogen fuel cells. One research focus in our group is the study of **proton transfer** **in bulk wate**r and **through membranes**. For this purpose we use molecular dynamics simulations based on empirical potentials as well as ab initio simulations.

### Nonlinear spectroscopy

Nonlinear response functions are commonly used in the interpretation of nonlinear optical and NMR experiments. One research goal of our group is to develop equilibrium and nonequilibrium simulation strategies for the calculation of such nonlinear response functions in **classical mechanical systems**.

### Nonlinear dynamics

The dynamics of complex systems is typically complicated by chaotic behavior. This **Lyapunov instability** is another central research theme in the Dellago group. Recent work includes the characterization of chaos in hard sphere fluids, the fractal analysis of nonequilibrium steady states, and the application of kinetic theory to chaos in dilute gases.

### Nanomaterials

When a crystal is reduced in size from macroscopic dimensions down to the molecular scale its physical and chemical properties can change dramatically. We use molecular dynamics and other more sophisticated simulation methodologies to study the morphology and structure of **gold nanoparticles** and pressure induced structural transitions in **semiconductor nanocrystals**