Intermetallic and Extraordinary Bonds of Beryllium and the Alkaline Earth Metals

该奖项由化学部门化学结构、动力学和机理a项目资助，埃默里大学的Michael C. Heaven教授和他的研究小组正在研究铍元素（Be）的不寻常的键合机制。一种常见的化学键被称为共价单键，其中两个电子由两个原子共享，这对电子中的每个原子通常为键贡献一个电子。铍原子的不寻常之处在于，它们经常形成所谓的对置共价键，即两个键的电子都是由另一个原子提供的。Heaven研究小组正在使用专门的激光和质谱仪来表征含有Be和其他金属原子的小分子的结构和性质（例如，BeLi, LiBeLi, Li4Be2，其中“Li”是锂原子）。由于铍的毒性，其化学性质尚未得到充分的研究。然而，Be及其化合物表现出独特而有用的性质。例如，铍合金由于其特殊的强度与重量比而被用作轻质结构材料。这种金属的显著耐久性反映在它被用作聚变反应堆的等离子体表面材料这一事实上。该研究项目提供了对化学键的新见解，以及可用于测试键合新理论的数据，并有助于预测用于新技术应用的新be化合物的性质。从事这个项目的研究生在实验化学和理论化学方面都获得了经验。来自亚特兰大大学中心联盟（AUCC）机构的本科生也参与了该项目。与AUCC机构的成功合作为来自传统黑人学院和大学（HBCUs）的本科生提供了研究机会。本科研究人员不仅要接受与Be化学相关的技术培训，还要培养软技能，如网络、论文准备和研究成果的口头展示。目前，评价铍量子化学模型所需的实验数据还很缺乏。这种验证需要建立对用于识别具有有价值的物理和化学性质的化合物的计算方法的信心。原型铍化合物的实验研究是本研究的主要目标。光谱学技术，包括激光诱导荧光（LIF）和脉冲场电离零电子动能（PFI-ZEKE）正在应用于气相分子和离子，以获得结构和热力学性质。选择LiBe（以及LiBe（+）、LiBe（-）、LiBe（+）等离子）和LiBeLi作为研究对象，是因为它们已经成为天堂实验室和其他机构进行高水平理论研究的对象。除了实验光谱工作外，该项目还采用了利用完全主动空间自一致场（CASSCF）和多参考构型相互作用（MRCI）的计算研究。本研究为研究生、本科生和博士后提供了丰富的先进实验和理论方法经验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.