Tang Carson L, Turney Justin M, Schaefer Henry F
Center for Computational Quantum Chemistry, Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2025 Aug 14;129(32):7507-7516. doi: 10.1021/acs.jpca.5c04243. Epub 2025 Aug 3.
Atmospheric iodine chemistry has garnered increasing attention as a result of increased iodine emissions. A key subset of this chemistry involves iodine oxides (IO), which serve as precursors to particle formation. Among these, IO is the simplest iodine oxide involved in particle formation, but it has remained undetected in the atmosphere. Previous theoretical studies have characterized this peculiar molecule, primarily using energies to refine geometries obtained at low levels of theory. Due to the reemerging interest in IO, this study presents geometries optimized at the CCSD(T)/aug-cc-pwCVTZ-PP level of theory─marking the first instance, to the best of our knowledge, where this system has been studied exclusively with CCSD(T). Harmonic vibrational frequencies were computed at the same level of theory. Final energetics were obtained using the very high level CCSDT(Q) method with basis sets up to quintuple-zeta cardinality (aug-cc-pwCV5Z-PP) and extrapolated to the CBS limit to yield CCSDT(Q)/CBS//CCSD(T)/aug-cc-pwCVTZ-PP energies. These energies include harmonic zero-point vibrational energy corrections and scalar relativistic energy corrections. Additionally, this study discovers new isomers along the IO potential energy surface, a novel contribution to the field. The performance of different computational methods and DFT functionals commonly used in atmospheric chemistry is also assessed relative to high-level theoretical methods.
由于碘排放增加,大气碘化学已受到越来越多的关注。这种化学过程的一个关键子集涉及碘氧化物(IO),它是颗粒形成的前体。其中,IO是参与颗粒形成的最简单的碘氧化物,但它在大气中一直未被检测到。先前的理论研究已经对这种特殊分子进行了表征,主要是利用能量来优化在低理论水平下获得的几何结构。由于对IO的兴趣再度兴起,本研究展示了在CCSD(T)/aug-cc-pwCVTZ-PP理论水平下优化的几何结构——据我们所知,这是首次对该体系仅使用CCSD(T)进行研究。在相同理论水平下计算了谐振动频率。最终能量学使用非常高的水平CCSDT(Q)方法获得,基组高达五重ζ基数(aug-cc-pwCV5Z-PP),并外推到CBS极限以产生CCSDT(Q)/CBS//CCSD(T)/aug-cc-pwCVTZ-PP能量。这些能量包括谐零点振动能量校正和标量相对论能量校正。此外,本研究沿着IO势能面发现了新的异构体,这是该领域的一项新贡献。相对于高水平理论方法,还评估了大气化学中常用的不同计算方法和DFT泛函的性能。