Lomboy Anna Joselle V, Topper Robert Q
Department of Chemistry and Department of Chemical Engineering, The Cooper Union for the Advancement of Science and Art, New York, New York 10003, United States.
Department of Chemistry, The Cooper Union for the Advancement of Science and Art, New York, New York 10003, United States.
J Phys Chem A. 2021 Apr 1;125(12):2546-2557. doi: 10.1021/acs.jpca.1c00732. Epub 2021 Mar 18.
Structural studies of ammonium halide nanoparticles can help to reveal fundamental information about the detailed nature of intermolecular forces. This study focuses on small ammonium fluoride clusters, which exhibit complex behavior in comparison to other ammonium halide clusters due to the weak acidity and strong hydrogen-bonding ability of HF. Calculations of optimized structures and binding energies are presented for cation, anion, and neutral clusters using MP2, CCSD(T), FNO-CCSD(T), ωB97M-V, and MN15 methods. The extent to which proton transfer occurs between two given cluster components was quantified using a dimensionless proton-transfer parameter (ξ), leading to a classification of different types of hydrogen bonds within the clusters. Whereas the neutral clusters exhibit a complex transition from ordinary hydrogen bonding to a combination of shared-proton hydrogen bonds and complete proton transfers, the anion and cation systems exhibit a rapid transition toward complete proton transfer from HF to NH, with incomplete proton transfer observed only in the smallest anion and cation clusters. Ionic interaction energies of these clusters were also computed and found to exhibit trends which can be interpreted by the size-dependent behavior of ξ. This work extends our understanding of the size-dependent trends in intermolecular forces which govern the formation of anhydrous ammonium halide clusters as well as the relationship between strong hydrogen bonding and proton transfer.
卤化铵纳米颗粒的结构研究有助于揭示有关分子间力详细性质的基本信息。本研究聚焦于小氟化铵团簇，由于HF的弱酸性和强氢键能力，与其他卤化铵团簇相比，它们表现出复杂的行为。使用MP2、CCSD(T)、FNO-CCSD(T)、ωB97M-V和MN15方法给出了阳离子、阴离子和中性团簇的优化结构和结合能计算结果。使用无量纲质子转移参数(ξ)对两个给定团簇组分之间发生质子转移的程度进行了量化，从而对团簇内不同类型的氢键进行了分类。中性团簇表现出从普通氢键到共享质子氢键和完全质子转移组合的复杂转变，而阴离子和阳离子体系则表现出从HF到NH的完全质子转移的快速转变，仅在最小的阴离子和阳离子团簇中观察到不完全质子转移。还计算了这些团簇的离子相互作用能，发现其呈现出可由ξ的尺寸依赖性行为解释的趋势。这项工作扩展了我们对控制无水卤化铵团簇形成的分子间力的尺寸依赖性趋势以及强氢键与质子转移之间关系的理解。
