Accurate ab initio determinations of thermochemical properties of environmental and biological molecular systems for benchmarking with experiments
EMSL Project ID
9591
Abstract
We propose to carry out high-level ab initio electronic structure calculations to study the chemistry of environmentally and biologically important molecular systems, which are relevant to the mission of the Department of Energy (DOE) and are of interest to the nation. The main goals of our proposed research are threefold: (1)We aim to obtain accurate ab initio determination of molecular structures, energetic properties such as heats of formation, ionization energies and bond dissociation energies, as well as spectroscopic properties including rotational constants, centrifugal distortion constants, vibrational frequencies and anharmonicities for a selected set of halogenated hydrocarbons and their cations; the corresponding experimental spectroscopic and energetic studies of these halogenated hydrocarbons will be carried out in the team leader's laboratory in Davis. The computational results will be useful in spectral simulations, assignments, and characterizations. In cases where the spectroscopic constants and thermochemical data are not known, the theoretical predictions are crucial to the experimental assignment and simulation.
(2)Through the comparisons between computational and experimental results, various theoretical methods and semi-empirical procedures (e.g., complete basis set extrapolation, Gaussian-n and Weizmann-n formalisms) will be evaluated and benchmarked. Furthermore, modifications will be performed on these theoretical methods and new approximation algorithms will be developed. The modifications and developments are aimed to improving the computational accuracy down to ~1 kJ mol-1 and the concomitant reduction of computational cost.
(3)Rigorous experimental investigations together with theoretical calculations on a series of amino acid molecules will allow the reliable determination of molecular structural parameters, thermochemical data, and spectroscopic constants for individual amino acids. The structural and energetic information obtained in this project will be used to modify and update the existing molecular mechanic force field parameterization database for peptides and proteins. The updated database is expected to be invaluable for studying protein folding and protein-ligand interaction.
All the computational results will be benchmarked and fully validated with the state-of-the-art experimental works carried out in the laboratory of the team leader. The experimental investigation features single-photon vacuum ultraviolet (VUV) as well as two-color infrared-VUV laser photoionization and photoelectron techniques for the spectroscopic studies of halogenated hydrocarbons and amino acid molecules. The resolutions achieved for VUV-photoionization and VUV-photoelectron measurements are 0.12 cm-1 and 1 cm-1, respectively. Previous studies indicate that spectroscopic and energetic data for polyatomic species can be determined to within 0.2 kJ mol-1. Such unrivaled precisions from experiments provide an ideal benchmarking tool to any high-level ab initio calculations. The proposed project will involve collaborations between the experimental group at the University of California at Davis and the theoretical groups at the National Center for Supercomputing Applications in Urbana-Champaign and the Chinese University of Hong Kong. Various quantum mechanical models (perturbation theory, density functional theory, coupled cluster, and multi-reference based configuration interaction methods) together with correlation-consistent basis sets will be employed to provide reliable computed results and the best possible comparisons with our experimental measurements.
Project Details
Project type
Capability Research
Start Date
2004-10-01
End Date
2006-10-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Aylward FO, KE Burnum, JJ Scott, G Suen, SG Tringe, SM Adams, KW Barry, CD Nicora, PD Piehowski, SO Purvine, GJ Starrett, LA Goodwin, RD Smith, MS Lipton, and CR Currie. 2012. "Metagenomic and metaproteomic insights into bacterial communities in leaf-cutter ant fungus gardens." The ISME Journal. doi:10.1038/ismej.2012.10 (Epub ahead of print)
Chundawat SP, MS Lipton, SO Purvine, N Uppugundla, D Gao, V Balan, and BE Dale. 2011. "Proteomics based compositional analysis of complex cellulase-hemicellulase mixtures." Journal of Proteome Research 10(10):4365-4372. doi:10.1021/pr101234z