Background:

• Fellowship of the American Physical Society, Chemical Physics,2001
• "Kilpatrick Lecture", Illinois Institute of Technology, 2000
• "Coulson Lecture", University of Georgia, 1998
• Distinguished Researcher Award, Bell Laboratories, 1987

Our research focuses on new developments in electronic structure theory along with challenging applications to investigate structures, chemistry, mechanisms, and properties of molecules and materials. Our work is collaborative and multidisciplinary, covering the areas of chemistry, physics, and materials science. Our research covers a broad spectrum of problems ranging from chemical bonding in small clusters to computational investigations of semiconductor and nanoscale materials.

Development of new methods in computational quantum chemistry. Electron correlation methods such as augmented coupled cluster theory have been developed to provide an accurate description of chemical bonding in molecules. Recent work has focused on developing composite models for accurate theoretical thermochemistry using traditional ab initio techniques as well as hybrid density functional methods. Extensions to heavier elements and development of new approaches applicable for larger molecules are active current topics.

Molecular applications. Innovative applications involving the structures, binding energies, vibrational and electronic spectra, and chemical reactivities of a wide variety of molecular systems are performed in our research group. Particular emphasis is placed on the prediction of structures and spectroscopic properties of novel species such as clusters. For example, the study of carbon clusters and fullerenes has been an ongoing active research area.

Materials applications. A particularly active research area concerns the development and application of cluster-based approaches to investigate the reactive chemistry of materials and surfaces. Many of these studies are carried out in close collaboration with experimental spectroscopic studies. For example, our investigations have unraveled the detailed mechanism of silicon oxidation including the identification of several key intermediates. Current emphasis is on designing embedding techniques to investigate chemical reactions in a variety of materials involving covalent, dative, and metallic bonding. Initial focus will be on understanding reactive processes such as chemical vapor deposition on semiconductor surfaces.

	Schematic view of water molecules approaching a reconstructed Si(100)-2x1 surface.

Selected Publications:

"Optical properties of point defects in SiO2 from time-dependent density functional theory," with D. Ricci and G. Pacchioni. J. Chem. Phys., 116, 825 (2002).

"Si-H bending modes as a probe of local chemical structure: thermal and chemical routes to decomposition of H2O on Si(100)-(2x1)," with M. K. Weldon, K. T. Queeney, A. B. Gurevich, B. B. Stefanov, and Y. J. Chabal. J. Chem. Phys., 113, 2440 (2000).

"Gaussian-3 (G3) theory for molecules containing first and second-row atoms," with L. A. Curtiss, P. C. Redfern, V. Rassolov, and J. A. Pople. J. Chem. Phys., 109, 7764 (1998).

"Electron correlation effects in molecules," with J. B. Anderson. J. Phys. Chem., 100, 12960 (1996).

"Isomers of C78: competition between electronic and steric factors," with C. M. Rohlfing. Chem. Phys. Lett., 208, 436 (1993).