Gregory Tschumper of the University of Mississippi has received an award from the Theory, Models and Computational Methods. The project focuses on high accuracy electronic structure characterization of molecular clusters held together by weak non-covalent interactions such as hydrogen bonding and dispersion interactions. Non-covalent clusters have significance in almost every area of the physical and biological sciences, playing key roles in everything from solvation to the physical, chemical, and electronic properties of materials in the solid phase.
The project has two goals: (1) Development and implementation of multi-centered (MC) integrated electronic structure methods (e.g., MO:MO, QM:QM, QM:MM and ONIOM) for the evaluation of molecular properties such as dipole moments, harmonic vibrational frequencies, NMR shielding constants among others; and (2) Application of the methodology for studying chemical physics of water clusters and micro-solvation phenomena. Of particular interest are the electronic and vibrational structure of water clusters at the crossover from 2D to 3D hydrogen bonding networks, the blue-shifted vibrational frequencies of azabenzenes in the condensed phase, and the relationship between the energy of complexation and solvent polarity for aromatic ¼-type interactions between "electron rich" 1,5-dialkoxynaphthalenes and "electron deficient" 1,4,5,8-naphthalenetetracarboxylicdiimides.Broader impact activities include a continued effort to mentor female and underrepresented students at the undergraduate and graduate level. Software developed during the project is made freely available. In addition, the large body of benchmark data generated as a by-product during the calibration of the MC integrated technique is collected, organized and distributed in a public and accessible database.
Research: Many important chemical, physical, and biological processes often depend more on what happens between molecules than within molecules. These "non-covalent" interactions influence a number of vital biological processes included protein folding, drug binding, molecular recognition and the stabilization of DNA and RNA structures. The insight into non-covalent interactions being gained from this work is fundamentally important to drug design, self-assembled nanomaterials, crystal engineering and even sensor technologies for biological and chemical agents. The research enabled by this award has led to the development of computational methods to accurately model these intermolecular interactions and their experimentally detectable manifestations. These new methods drastically reduce the computational demands of the most reliable quantum mechanical models so that the necessary computations can be performed routinely on modest resources (like those often found in individual research labs or small departments) rather than requiring a world-class supercomputer. Education: Thirteen undergraduate students and nine graduate students were directly (stipends) and indirectly (supplies, computational resources, etc.) supported by this research program. During the award period, six of these undergraduate students (four of whom are female) obtained their bachelor's degrees while majoring in chemistry. These students gained valuable research skills and experience in the PI's lab that will help them as they seek post-baccalaureate degrees. Two women also obtained their doctorates under the PI's direction in that time frame, and two more earned their master's degrees. Dr. Kari Copeland completed the doctoral program in 2012, and she was one of five African American Ph.D. students (including 3 women) who earned their chemistry doctorates in 2012-2013 from the PI's department at the University of Mississippi. (See Figure 1.) Kari is currently a post-doc in the lab of Glake Hill at Jackson State University, an HBCU in Jackson, MS. Outreach: The PI has taken numerous steps to increase public awareness of the important roles that modeling and simulation play in the modern scientific process. All honors sections of general chemistry (or "freshman" chemistry) taught by the PI include a series of computational chemistry modules designed to reinforce learning objectives related to basic molecular shape and intermolecular forces. Working with a team from Research Media Ltd., the PI developed a nontechnical write-up of this NSF funded research program that can be found online and free of charge in the January 2013 issue (#18, pages 59-62) of International Innovation. The PI also gave overview of computational science and supercomputing to the general public at a local science cafe in November 2012. The very diverse audience included everyone from middle school students to retired faculty. One high school student at the talk is now attending the University of Mississippi and is now interested in pursuing a degree in chemistry.
