The tools of our laboratory are paper, pencils, and digital computers. Some of the computers that we use are in the Chemistry Department; others are in the campus Advanced Computing Facility, which has just acquired major new equipment; yet others are in off-campus supercomputing centers. We are theoretical and computational chemists. Our main interests are in the motions of molecules and in the motions of atoms within molecules.

We study rotational-vibrational energy levels of individual molecules by quantum mechanical techniques. The aim of such studies is, in part, to find efficient methods to carry out these studies. On the other hand, techniques already available are being used to study the interaction between rotations and vibrations and also the effect of molecular potential functions on molecular energy levels.

We study the properties of large aggregates of molecules by integrating in time the equations of motion of the atoms in a system, subject to given forces, to obtain a trajectory for the system. This technique is known as the molecular dynamics (MD) technique. MD can be routinely employed for systems as large as a few thousand atoms. Under appropriate conditions, such a system can simulate a liquid, or a solid, or a surface. We have studied the properties of aqueous solutions as well as the vibrations of surfaces of crystals and of atoms adsorbed on these surfaces. We have investigated col lisions of a beam of molecules with a crystal and studied the details of both elastic processes and molecule-crystal chemical reactions. We are currently studying the motions of atoms in a liquid of long alkane chains and also of large cyclic alkanes. These latter studies are preparing us for undertaking calculations on large molecules which are of biological interest.

When an atom in a molecule is replaced by an isotopic atom (say, a hydrogen atom by a deuterium atom), the resulting effect on molecular properties is an isotope effect. Isotope effects on chemical rates, equilibria, polarizabilities, vapor pressures, and the like, follow from the effect of mass on the motions of atoms. Our interests in atomic motions have led to a parallel interest in the elucidation of isotope effects.