Home >> Summer Program Home >> Research
  Login

Research at the CCC

The Center for Computational Chemistry at the University of Georgia seeks to develop theoretical and computational methods through mathematical models for describing and understanding the electronic structure of molecules. The members of the CCC utilize the tools of quantum chemistry to gain a greater understanding of the underlying processes of chemistry. This endeavor is supported by a number of key research areas and facilities.

Applications of Quantum Chemistry

The majority of active research at the CCC involves the application of ab initio quantum chemistry to molecular systems. Application of quantum chemical calculations to real chemical systems represents the essence of computational chemistry. Modeling chemistry through quantum mechanics can provide important properties such as the structure of a molecule, vibrational frequencies, and charge distributions. Properties such as the electronic structure and excited state information cannot be determined from molecular mechanics simulations, and ab initio theory provides the only means by which chemists can obtain this information from a theoretical perspective. A wide variety of theoretical methods, including density functional theory (DFT), coupled-cluster (CC), and configuration interaction (CI) theories are employed in our studies. Our research encompasses a wide range of chemical problems including:

  • Determination of solvent effects on SN2 reaction pathways
  • Metal-metal and metal-ligand bonding in organimetallic compounds
  • Determining ab initio limits for combustion and soot energetics
  • Sysmematic examination of molecular electron affinities with DFT
  • Identification of interstellar molecules and ions
  • The Renner-Teller effect
  • Relativistic corrections
  • Gallium-nitride and related nanorods
  • Lesions in DNA subunits
  • Effects of perfluoro compounds on global temperature patterns

Method Development

The CCC is at the forefront of method development in quantum chemistry with the programming package PSI. PSI is the center's own computational quantum chemistry program suite that includes capabilities such as self-consistent field, configuration interaction, multi-reference CI (MRCI), coupled-cluster, and explicitly-correlated computations. PSI provides group members an environment in which to build quantum chemical code with a suite of packages already available to them for development. Current development projects include:

  • MP-R12 and CC-R12 methods for highly accurate computations explicity utilizing the interelectronic coordinate
  • Multireference coupled-cluster and perturbation theories
  • Spectroscopic simulations via the vibronic coupling scheme
  • Relativistic corrections
  • NMR chemical shifts

Collaboration

Science is not performed in a vacuum and collaboration is an essential aspect of research. The CCC has correspondence with many well-known chemical research groups, both experimental and theoretical, from around the world. A few of the group's collaborators include:

  • Professor Nicholas C. Handy, University of Cambridge, England
  • Professor William H. Miller, University of California at Berkeley
  • Professor Martin Quack, Eidgenössische Technische Hochschule (ETH), Zürich
  • Professor Leo Radom, University of Sydney
Many members of the group and summer students have attended quantum chemistry conferences in the past in order to lecture and promote the research sponsored by the CCC. These conferences included:
  • Molecular Quantum Mechanics: : Analytic Gradients and Beyond, Budapest, Hungary, May 2007
  • 37th Southeastern Theoretical Chemistry Association, Virginia Tech University, June 2007
  • 7th World Congress of Theoretically Oriented Chemists, Cape Town, South Africa, January 2005

Computational Facilities

The CCC has a wide variety of computing power available for research use. Much of the work is carried out on our cluster of Linux based PC’s connected via fast Ethernet. The cluster currently consists of 60 Pentium 4 machines, with clock speeds ranging from 2.5 to 3.2 GHz and equipped with 1 to 3 GB of RAM. We have a rack-mounted cluster of 21 dual Opteron (2.2 GHz) nodes featuring 6 GB of RAM per node and 14 dual 2.6 GHz dual-core Opteron nodes with 16 GB of RAM per node and 500 GB scratch space. Each node is connected via Gigabit interconnect and equipped with high-speed SCSI hard drives. We recently acquired 13 new dual 3.0 GHz dual-core Opteron nodes with 16 GB each of RAM with 500 GB of scratch space. These nodes are connected together via Infiniband.

Recently, the CCC has also moved to a strategy in which each group member is issued a ‘dream machine,’ which is a high-end workstation, configured and maintained by each individual. These machines serve as terminals to access our ever-expanding cluster resources, provide a development platform, and run computations. A typical configuration for one of these workstations includes dual 3.0 GHz dual-core Opteron processors, 32 GB of RAM, a 500 GB hard drive, and a dual-screen display with 19-inch flat-panel monitors.

Along with PSI, the CCC uses a number of other computational chemistry software packages, including Gaussian 94, Q-Chem 3.1, ACES II, MPQC, MOLPRO, and NWChem.

Research Philosophy

The scope and caliber of the CCC's applications of electron structure theory to chemistry are unusual. Since its inception, the research undertaken has been timely and of broad chemical interest. Thoroughness is a valuable quality in group members, for applications work requires both an understanding of the theoretical methods used as well as a healthy familiarity with the corresponding experiments.

The most visible result of this approach has been the reversal of the conclusions of a number of distinguished experimentalists. Subsequent experimental studies have verified controversial predictions concerning the structure and singlet-triplet separation of methylene, the quadruple moment of ozone, the activation energy for D + HF exchange, and the vibrational spectrum of benzyne, to cite just a few. Equally important has been the manner in which the work in the Schaefer group has guided experimentalists into new directions. A recognized early example [Nature, 278, 507 (1979)] was the identification of the spectrum of triplet acetylene.

The tradition of serious methods development combined with thoughtful applications research continues at the Center for Computational Chemistry.

Some Recent Publications

  • “High-Order Excitations in State-Universal and State-Specific Multireference Coupled Cluster Theories: Model Systems,” F. A. Evangelista, W. D. Allen, and H. F. Schaefer, J. Chem. Phys. 125, 154113 (2006).
  • “Coupling Term Derivation and General Implementation of State-Specific Multireference Coupled Cluster Theories,” F. A. Evangelista, W. D. Allen, and H. F. Schaefer, J. Chem. Phys. 127, 024102 (2007).
  • “Carbene Stabilization by Aryl Substituents: Is Bigger Better?” H. L. Woodcock, D. Moran, B. R. Brooks, P. R. Schleyer, and H. F. Schaefer, J. Am. Chem. Soc. 129, 3763 (2007).
  • “Ionization Thresholds of Small Carbon Clusters: Tunable VUV Experiments and Theory,” L. Belau, S. E. Wheeler, B. W. Ticknor, M. Ahmed, S. R. Leone, W. D. Allen, H. F. Schaefer, and M. A. Duncan, J. Am. Chem. Soc. 129, 10229 (2007).
  • “Electron Attachment Induced Proton Transfer in a DNA Nucleoside Pair: 2′-Deoxyguanosine (dG) --2′-Deoxycytidine (dC),” J. Gu, Y. Xie, and H. F. Schaefer, J. Chem. Phys. 127, 155107 (2007).
  • “A Stable Neutral Diborene Containing a B = B Double Bond,” Y. Wang, B. Quillian, P. Wei, C. S. Wannere, Y. Xie, R. B. King, H. F. Schaefer, P. R. Schleyer, and G. H. Robinson, J. Am. Chem. Soc. 129, 12412 (2007).
Contact | Center for Computational Chemistry, 1004 Cedar St., The University of Georgia, Athens, GA 30602-2556, Tel: (706) 542-2067 Fax: 0406
The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.