Quantum effects become important in nanoscale systems such as molecules and clusters, which consist of a few to a few thousand atoms. The structure (how the atoms are arranged within the cluster), electronic and optical properties (for example, at what wavelengths they absorb or emit light) of these systems can be size dependent, and significantly different from the properties of the bulk materials. Clusters have recently captured considerable attention as it was realized that their properties could be tuned with size, leading to new applications with potential impact in almost all fields of science and technology: medicine, information technology, manufacturing, environmental protection, and homeland security, among others. None of the above would be possible without experimental research that can develop techniques for creating, manipulating, and studying these novel materials, and without the theoretical research that can help explain and predict their properties.
We use ab initio methods to calculate the electronic and optical properties of molecules and clusters. Ab initio, or first-principles, methods referes to the fact that we don't use empirical parameters or extrapolations based on bulk properties in our calculations - we do calculations starting from the basic properties of atoms and quantum mechanics. In particular, we use the real-space method within density functional theory (DFT), as well as time-dependent density functional theory (TDDFT) and many-body methods to study the properties of atomic clusters. This methods are implemented in a computer program called PARSEC.
Our calculations involve numerically solving a complicated eigenvalue equation, which requires a lot of computer time and memory. We are currently building a 16-processor computer cluster at the University of St. Thomas that we will use in this research project as well as make available for projects from other UST departments.