To perform calculations to optimise and test our algorithm we must decide on our energy calculator. Ideally, we would use DFT to geometry optimise all structures however performing tens of thousands of DFT local relaxations is computationally expensive and unnecessary to assess the algorithm performance. Instead, we test three candidate 'fast' energy calculators to perform these test and further assessments. We perform 901 local optimisation calculations for Pt 13 H 4 structures generated by distributing H 2 molecules on the surface of a Pt NP (c.f. section 2.3) with ONETEP. we then compares the energetic ordering of locally optimised ONETEP structures to locally optimised equivalents using xTB (c.f. section 2.4.1), MACE-MP-0 foundation model, and effective medium theory (EMT) as energetic evaluators.