Professor Oppenheim's research is in the area of theoretical physical chemistry and, in particular, statistical mechanics. The aim of this research is to study and understand the molecular foundations of the macroscopic behavior of chemical systems. There are several major areas currently under investigation.

The first area is the study of time-dependent properties of fluid systems. These include the properties of nonequilibrium systems and time-dependent correlations in equilibrium and steady-state systems. The particular fields studied include hydrodynamics, diffusion controlled reactions, spectroscopic line broadening phenomena and NMR. In addition, transitions from one steady state to another are under investigation.

The second major area of study is the time-dependent properties of fluid-fluid and fluid-solid surfaces. Surface properties are special because of the lack of symmetry that exists. These investigations have importance in the study of surface specific reactions and heterogeneous catalysis.

Finally, we are studying granular and two-phase flow emphasizing the differences of behavior between granular and molecular systems.