ONETEP is a linear-scaling density functional theory (DFT) method. It is based on reformulating DFT in terms of the one-particle density matrix. This matrix is expressed in terms of an atom-centred, non-orthogonal generalised Wannier functions (NGWFs). The NGWFs are in turn expanded with a basis set of periodic sinc (psinc) functions which are related to plane waves through a unitary transformation. This allows us to truncate the one-particle density matrix and thus achieve linear scaling for large enough systems. We used on-thefly norm-conserving pseudopotentials were generated using CASTEP and a 830 eV kinetic energy cutoff for the psinc basis set. The electron density of Pt atoms was characterized using 13 NGWFs, while 1 NGWF was used for each H atom in the system. The NGWF radii were set to 10 a0 ( 5.29 Å). The PBE functional was selected to calculate the energy of electron exchange and correlation interactions. The ensemble DFT method, as implemented in ONETEP, was used to converge the energy calculation due to the likelihood that the systems we produce will be non-gapped. We limited ensemble DFT to 10 iterations, set the smearing width to 0.1 eV, and used the Pulay mixing method to accelerate convergence.