The Bristol & Oxford Chemical Dynamics Group

Integrated electronic structure theory and dynamical methods for modelling chemical reactivity and dynamics.

Most of the experimental work will be complemented by theoretical and computational studies designed to attain a deeper and critical interpretation of the phenomena of interest. The two prerequisites of such theoretical calculations are the potential energy surface (PES), which characterises the interactions within the reacting system, and a suitable method for propagating the system on the PES. These are mutually interlinked and can pose considerable computational challenge. The aim of this work package extends way beyond simply delivering these two objectives for particular systems. Specifically, we plan to develop methodologies by which both constructing the PES and performing the dynamical simulations become less onerous and time consuming activities. Primary concerns are to increase the speed of such calculations by exploiting the transferability between models of gas and liquid phase systems, and between systems of differing complexity, and increasing the automation and inter-linkages between the various computational tasks.

Depending of the desired accuracy, a variety of methods will be used to construct the PESs, including ab initio electronic structure and density functional calculations, while the dynamical calculations will focus on the use of classical and semi-classical propagators of codes developed or modified by the participating groups. We plan extensive investigations of empirical valence bond (EVB) and polynomial PESs, and of the related dynamics computer codes, in an effort to achieve the above aims.

Empirical valence bond (EVB) Hamiltonian matrix. The EVB formalism reduces the computational burden by using molecular mechanics force fields and dividing the system into smaller subsystems whose energies are represented in the diagonal of the matrix (JCP 134 214508, (2011)). .
Vibrational energy distribution of the product HCN molecule formed in the C6H6 + CN -> C6H5 + HCN gas phase reaction calculated with EVB method (JCP 134 214508, (2011)).

Further Information