Intermetallic and Extraordinary Bonds of Beryllium and the Alkaline Earth Metals

Emory University, Atlanta GA

Investigators

Abstract

In this award, funded by the Chemical Structure, Dynamics and Mechanisms-A Program of the Chemistry Division, Professor Michael C. Heaven and his research group at Emory University are investigating the unusual bonding mechanisms of the element beryllium (Be). A common type of chemical bond is called a covalent single bond, where two electrons are shared by two atoms, each atom of the pair typically contributing one electron to the bond. Beryllium atoms are unusual in that they often form what are called dative covalent bonds, where both bonding electrons are provided by the other atom. The Heaven research group is using specialized lasers and mass spectrometers to characterize the structure and properties of small molecules containing Be and other metal atoms (e.g., BeLi, LiBeLi, Li4Be2, where "Li" is a lithium atom). The chemistry of beryllium is underexplored due to its toxicity. However, Be and its compounds exhibit unique and useful properties. For example, beryllium alloys are used as lightweight structural materials due to their exceptional strength to weight ratios. The remarkable durability of the metal is reflected by the fact that it is used as a plasma facing material in fusion reactors. This research project is providing new insights into chemical bonding in general, as well as data that can be used to test new theories on bonding and help in the prediction of the properties of new Be compounds for new technological applications. The graduate students engaged in this project are gaining experience in both experimental and theoretical chemistry. Undergraduate students from the Atlanta University Center Consortium (AUCC) institutions are also involved in the project. This successful collaboration with AUCC institutions provides research opportunities for undergraduate students from Historically Black Colleges and Universities (HBCUs). Undergraduate researchers are not only receiving technical training related to Be chemistry, but also developing soft skills, such as networking, manuscript preparation and oral presentation of research results. At present, the experimental data needed to evaluate quantum chemical models for beryllium are lacking. This validation is needed to establish confidence in the computational methods used to identify compounds with valuable physical and chemical properties. Experimental studies of prototypical beryllium compounds are the primary objectives of this research. Spectroscopic techniques, including laser-induced fluorescence (LIF) and pulsed-field ionization-zero electron kinetic energy (PFI-ZEKE) are being applied to gas phase molecules and ions to obtain structural and thermodynamic properties. The species being examined, including LiBe (and ions LiBe(+), LiBe(-)) and LiBeLi are chosen because they have been the subjects of high-level theoretical investigations in the Heaven laboratory and by others. In addition to the experimental spectroscopic work, this project employs computational studies that utilize complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI). The research provides the graduate and undergraduate students, and post-doctoral associates involved with a rich experience in advanced experimental and theoretical methods. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.