The Rattling and Rotation Behaviours of the Hydrated Excess Proton in Water

2019-05-28T14:40:49Z (GMT) by Shuping Bi
<p><b>The rattling and rotation behaviours of the hydrated excess proton (H<sup>+</sup>) in water are investigated using the density functional theory–quantum chemical cluster model (DFT-CM) method. The rattling pathways for the target proton <sup>*</sup>H<sup>+</sup> between two adjacent O atoms in the form of Zundel configurations with symmetrical solvation environments are obtained. The zero-point contribution reduces the reaction energy barrier and enables the rattling to occur spontaneously at room temperature. The rotational behaviour of <sup>*</sup>H<sup>+</sup> in the form of <sup>*</sup>H<sup>+</sup>·H<sub>2</sub>O<sup>*</sup> is found. Upon <sup>*</sup>H<sup>+</sup>·H<sub>2</sub>O<sup>* </sup>rotation, <sup>*</sup>H<sup>+</sup> changes its position accompanied by concerted displacement of surrounding solvent water molecules and the breaking and formation of hydrogen bonds. The “<sup>*</sup>H<sup>+</sup>·H<sub>2</sub>O<sup>*</sup> rotating migration mechanism” is proposed for the proton transfer mechanism in water — the same <sup>*</sup>H<sup>+</sup> migrates via <sup>*</sup>H<sup>+</sup>·H<sub>2</sub>O<sup>*</sup> rotation through void in solvent water, rather than different protons hopping along water hydrogen bond chains as known as the Grotthuss mechanism.</b></p><p><b> </b></p>