Catalytic effects of magnesium grain boundaries on H2 dissociation

• The dissociation barrier for H2 in a certain Mg grain boundary has been calculated.
• The dissociation rate in a GB is increased by a factor 25 compared to the surface.
• The diffussion of H in and out of the GB plane is calculated.

The influence of a Σ10(112¯4)/[11¯00] grain boundary in magnesium on the dissociation of the hydrogen molecule has been investigated by ab initio calculations. It is found that the dissociation barrier is indeed lowered by 0.115 eV, including zero point motion, compared to the clean surface. This results in a 25 fold increase in the transition rate, at desorption temperature of 572 K. Furthermore, different diffusion paths of hydrogen in and out of the grain boundary plane are investigated.