Sharma Bikramjit, Chandra Amalendu
Department of Chemistry, Indian Institute of Technology Kanpur 208016, India.
J Phys Chem B. 2020 Apr 2;124(13):2618-2631. doi: 10.1021/acs.jpcb.9b12008. Epub 2020 Mar 20.
The iodate ion has an anisotropic structure and charge distribution. It has a pyramidal shape with the iodine atom located at the peak of the pyramid. The water molecules interact differently with the positively charged iodine and the negatively charged oxygen atoms of this anion, giving rise to two distinct solvation shells. In the present study, we have performed ab initio Born-Oppenheimer molecular dynamics simulations to investigate the dynamics of water molecules in the iodine and oxygen solvation shells of the iodate ion and compared the behavior with those of the bulk. The dynamics of water is calculated for both the BLYP and the dispersion-corrected BLYP-D3 functionals at room temperature. The dynamics of water in the solvation shells at higher temperatures of 353 and 330 K has also been investigated for the BLYP and BLYP-D3 functionals, respectively. The hydrogen bond dynamics, vibrational spectral diffusion, orientational and translational diffusion, and residence dynamics of water molecules in the two solvation shells are looked at in the current study. The ion-water hydrogen bond dynamics is found to be somewhat faster than that for water-water hydrogen bonds in the bulk, which can be attributed to a ring-like electron distribution on the iodate oxygens. The dynamical trends are connected to the water structure making/breaking properties of the positively charged iodine and negatively charged oxygen sites of the anion. Furthermore, orientational jumps of the iodate ion and also those of surrounding water molecules which are hydrogen bonded to the oxygen atoms of the iodate ion are also investigated. It is found that the nature of these orientational jumps can be different from those reported earlier for planar polyoxyanions such as the nitrate ion.
碘酸根离子具有各向异性的结构和电荷分布。它呈金字塔形状，碘原子位于金字塔顶端。水分子与该阴离子带正电的碘和带负电的氧原子的相互作用方式不同，从而产生了两个不同的溶剂化壳层。在本研究中，我们进行了从头算的玻恩 - 奥本海默分子动力学模拟，以研究碘酸根离子的碘和氧溶剂化壳层中水分子的动力学，并将其行为与本体水的行为进行比较。在室温下，针对BLYP和色散校正的BLYP - D3泛函计算了水的动力学。还分别针对BLYP和BLYP - D3泛函研究了在353 K和330 K的较高温度下溶剂化壳层中水的动力学。本研究考察了两个溶剂化壳层中水分子的氢键动力学、振动光谱扩散、取向和平动扩散以及停留动力学。发现离子 - 水氢键动力学比本体水中水 - 水氢键动力学稍快，这可归因于碘酸根氧原子上的环状电子分布。动力学趋势与阴离子带正电的碘和带负电的氧位点的水结构形成/破坏性质相关。此外，还研究了碘酸根离子以及与碘酸根离子的氧原子形成氢键的周围水分子的取向跳跃。发现这些取向跳跃的性质可能与先前报道的平面聚氧阴离子（如硝酸根离子）的不同。
