Catalytic effects of magnesium grain boundaries on H 2 dissociation

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.