A full-dimensional quantum dynamical study of the vibrational ground state of $H_3O_2^-$ and its isotopomers

TL;DR

This study uses advanced quantum dynamical methods to analyze how deuteration affects the vibrational ground state and stability of the hydrated hydroxide anion and its isotopomers, revealing isotope effects on energy and geometry.

Contribution

It provides a detailed quantum dynamical analysis of isotope effects on the vibrational ground state of H3O2- and its isotopomers, including zero-point energies and geometric changes.

Findings

Isotopomers with bridging hydrogen are more stable by about 1 kJ/mol.

Deuteration causes elongation of the O--O distance by 0.005 to 0.009 Å.

Ground state tunneling splitting varies with isotopomer due to torsional motion.

Abstract

We investigated the effect of deuteration on the vibrational ground state of the hydrated hydroxide anion using a nine-dimensional quantum dynamical model for the case of J=0. The propagation of the nuclear wave function has been performed with the multi-configuration time-dependent Hartree method which yielded zero-point energies for the normal and fully deuterated species in quantitative agreement with previous diffusion Monte Carlo calculations. According to the zero-point energy the isotopomers having the hydrogen atom in the bridging position are more stable by about 1 kJ/mol as compared to the deuterium case. This holds irrespective of the deuteration state of the two OH groups. We also report the secondary geometric H/D isotope effect on the O--O distance which amounts to an elongation of about 0.005 A for the symmetric isotopomers and 0.009 A in the asymmetric case. Finally, we explore the isotopomer sensitivity of the ground state tunneling splitting due to the torsional motion of the two OH groups.