Rotation of hydrogen molecules during the dissociative adsorption on the Mg(0001) surface: A first-principles study

TL;DR

This first-principles study reveals how hydrogen molecules rotate during dissociative adsorption on Mg(0001), affecting energy barriers and electronic interactions, providing insights into surface chemistry mechanisms.

Contribution

The paper uncovers the rotation behavior of hydrogen molecules during dissociation on Mg(0001) and explains its electronic basis, which was not previously understood.

Findings

Hydrogen molecules initially orient perpendicular before rotating parallel during adsorption.

Rotation reduces the dissociation energy barrier for hydrogen molecules.

The orientation at the transition state differs from initial and final states.

Abstract

Using first-principles calculations, we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg(0001) surface. It is found that during the dissociative adsorption process with the minimum energy barrier, the hydrogen molecule firstly orients perpendicular, and then rotates to be parallel to the surface. It is also found that the orientation of the hydrogen molecule at the transition state is neither perpendicular nor parallel to the surface. Most importantly, we find that the rotation causes a reduction of the calculated dissociation energy barrier for the hydrogen molecule. The underlying electronic reasons for the rotation of the hydrogen molecule is also discussed in our paper.