Department of Chemistry & Biochemistry, University of Mississippi, University, Mississippi 38677-1848, United States.
J Phys Chem A. 2021 Jun 3;125(21):4589-4597. doi: 10.1021/acs.jpca.1c02878. Epub 2021 May 24.
Crystallization of carbonic acid likely begins with a linear or ribbon-esque oligomerization, but a helical spiral is shown here to be a new, competing motif for this process. The present combined density functional theory and coupled-cluster theory work examines both the ribbon and the new helical spiral motifs in terms of relative energies, sequential binding energies, and electronic spectra which could potentially aid in distinguishing between the two forms. The helix diverges in energy from the ribbon by roughly 0.2 eV (∼4 kcal/mol) per dimer addition, but the largest intensity absorption features at 9.16 eV (135 nm) and 7.11 eV (175 nm), respective of the ribbon and spiral, will allow these to be separately observed and classified via electronic spectroscopy to determine more conclusively which motif holds in the earliest formation stages of solid carbonic acid.
碳酸的结晶可能首先经历线性或带状寡聚化，但此处显示螺旋形是该过程的新的竞争模式。目前的组合密度泛函理论和耦合簇理论研究从相对能量、顺序结合能和电子光谱方面考察了带状和新螺旋形模式，这些可能有助于区分这两种形式。螺旋形相对于带状每增加一个二聚体，能量相差约 0.2eV（约 4kcal/mol），但最大强度的吸收特征分别位于 9.16eV（135nm）和 7.11eV（175nm）处，分别对应于带状和螺旋形，这将允许通过电子光谱分别观察和分类，以更确定地确定在固体碳酸的最早形成阶段哪种模式存在。
