Ab initio molecular dynamics investigation of structural, dynamic and spectroscopic aspects of Se(vi) species in the aqueous environment

Abstract

Microscopic investigation of solvation of selenic acid (H₂SeO₄) in the aqueous environment has been carried out using the Car–Parrinello molecular dynamics simulation technique. The species deprotonates to HSeO₄⁻ in a few picoseconds owing to its low pK_a1 value of −3.0. A dynamic equilibrium between HSeO₄⁻ and SeO₄²⁻, is observed in qualitative agreement with the reported pK_a2 value of 1.70. The governing deprotonation mechanism and the structural and dynamic evolutions of the system, particularly the nature of hydrogen bonding, their strengths and lifetimes are investigated comprehensively. A comparison of the vibrational spectra of the species recorded in the gas phase and in the aqueous environment provides further insights on the nature of the interaction between the solute species and water. The results are in good agreement with the available experimental data and other recent computational studies.