Here we use a pre-optimised structure of a GM Pt 13 and H 2 molecules to initiate globally optimised structures. From this investigation we can observe which sites and H 2 orientations are favourable for adsorption on the particle. Next, we use the 'in-sphere' structure generator which distributes the atoms within a sphere, this will find the GM structure irrespective of ideal molecule/NP configurations. This is done to simulate how the NP may look after adsorption has taken place and the reaction has cleaved the H 2 bond. We could use these structures can in turn be used to determine the desorption energies of the H atoms. With both these structures a full reaction path for H 2 desorption on can be determined.