Research topics in the theoretical chemistry group

Intermolecular force fields

Intermolecular potential surfaces or, as they are often called, noncovalent force fields, determine many properties of matter. They include both weak Van der Waals forces and hydrogen bonding, which lead to the formation of supramolecular systems and play an important role in most biological processes. A longstanding activity of the Theoretical Chemistry group is the ab initio calculation of intermolecular potentials by quantum mechanical methods for a series of well-chosen model systems, also studied experimentally. The methods used are either based on symmetry-adapted perturbation theory (SAPT, for closed-shell systems) or on supermolecular coupled-cluster methods (for both open- and closed-shell systems).

Dynamics of molecular clusters and collisional processes

The intra- and intermolecular energy transfer and relaxation processes that occur in molecular aggregates when they are excited or when the molecules collide are very interesting. State-to-state studies by molecular beam techniques and laser spectroscopy provide detailed information on these processes, but theory is needed to understand what happens and to relate the observed properties to the underlying intermolecular force fields. The Theoretical Chemistry group performs quantum dynamics calculations for bound states and photodissociation of Van der Waals and hydrogen bonded clusters, as well as for (in)elastic molecular scattering. At the same time, since intermolecular forces cannot be directly measured, it is very useful that the comparison of the results of dynamics calculations with experimental data provides a critical test of the intermolecular potentials. Also aggregates containing (unstable) radicals or electronically excited species are being investigated.

State-to-state chemical reactions; theoretical approach.

Experimentally, chemical reactions can be studied at the state-to-state level in molecular beams. To guide and interpret such experiments theoretical studies are indispensable. We have been working on the development and application of time-independent and time-dependent quantummechanical methods and also on semiclassical and quasiclassical methods. Particularly the quantummechanical methods are very compute-intensive, but also semiclassical calculations become more and more demanding if the number of coordinates treated quantummechanically increases. Standard program packages are not available and software development is an important part of the work. Recently, our research has focussed on (in)elastic and reactive collisions of ultracold molecules and radicals, which can be extremely well controlled with the use of electric and magnetic fields.
Recent publications
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Last updated: January 16, 2007, by Gerrit C. Groenenboom, e-mail: