Time-dependent density functional theory investigation of the formation of H$^{3+}$ from alkanes

TL;DR

This study uses time-dependent density functional theory to explore how H$^{3+}$ ions form from different alkane dications, revealing distinct pathways and branching ratios for ethane, propane, and butane.

Contribution

It introduces a TDDFT-based method to simultaneously analyze electronic and nuclear dynamics in alkane dications, elucidating formation mechanisms of H$^{3+}$ ions.

Findings

Ethane and propane have similar H$^{3+}$ formation branching ratios.

Butane shows a lower H$^{3+}$ formation branching ratio.

Ethane follows the minimum-energy pathway, while propane involves H$_2$ roaming.

Abstract

The formation of H$^{3+}$ from ethane, propane, and butane dications was investigated with time-dependent density-functional theory (TDDFT) simulations. This approach offers the benefit of simultaneously addressing nuclear and electronic dynamics, enabling the investigation of electronic excitation, charge transfer, ionization, and nuclear motion. For each dication we determined the ground-state HOMO, the branching ratios of all dissociation channels, and the mechanism leading to H$^{3+}$. The simulated branching ratios for ethane and propane are similar, while butane is markedly lower. Ethane follows the minimum-energy pathway (MEP) proposed previously; propane forms H$^{3+}$ mainly via H$_2$ roaming. In butane, H$^{3+}$ appears only through the MEP within the present trajectory set; roaming H$_2$ was not observed under the same conditions.