Minimalistic Descriptions of Nondynamical Electron Correlation: From Bond-Breaking to Transition-Metal Catalysis

From a theoretical standpoint, the accurate description of potential energy surfaces for bond breaking and the equilibrium structures of metal-ligand catalysts are distinctly similar problems. Near degeneracies of the bonding and anti-bonding orbitals for the case of bond breaking and of the partially-filled d-orbitals for the case of metal-ligand catalyst systems lead to strong non-dynamical correlation effects. Standard methods of electronic structure theory, as a consequence of the single-reference approximation, are incapable of accurately describing the electronic structure of these seemingly different theoretical problems. The work within highlights the application of multi-reference methods, methods capable of accurately treating these near-degeneracies, for describing the bond-breaking potentials in several small molecular systems and the equilibrium structures of metal-salen catalysts. The central theme of this work is the ability of small, compact reference functions for accurately describing the strong non-dynamical correlation effects in these systems.Ph.D.Committee Chair: C. David Sherrill; Committee Member: Jean-Luc Bredas; Committee Member: Mostafa El-Sayed; Committee Member: Peter J. Ludovice; Committee Member: Thomas Orland

A framework for execution of computational chemistry codes in grid environments

International audienceGrid computing is a promising technology for computational chemistry, due to the large volume of calculations involved in appplications such as molecular modeling, thermochemistry and other types of systematic studies. Difficulties in using computational chemistry codes in grid environments arise, however, from the fact that the application software is complex, requiring substantial effort to be installed on different platforms. Morever, these codes depend upon task-dependent sets of data files to be present at the execution nodes. Aiming to improve the usability of different quantum chemistry codes in the distributed, heterogeneous environments found in computational grids, we describe a framework capable of handling the execution of different codes on different platforms. This framework can be divided into three independent parts, one dealing with the mapping of a calculation to a set of codes and the construction of execution environments, one dealing with the management of grid resources, and one that takes care of the heterogeneity of the environment. The suitability of this framework to tackle typical quantum chemistry calculations is discussed and illustrated by a model application