This supplementary information contains the files necessary to reproduce DFT calculations contained in the publication titled "Unravelling the epitaxial growth mechanism of hexagonal and nanoporous boron nitride: A first-principles microkinetic model". Please see the README for coordinate files and corresponding total energies of all structures in the article (in 'Structure_files.zip'), including geometry optimisations and transition states of the reaction mechanisms using the CASTEP program. This work made use of ARCHER2, the UK’s national high-performance computing service, via the UK’s HPC Materials Chemistry Consortium, which is funded by EPSRC (EP/R029431 and EP/X035859) and Eureka, the University of Surrey’s High-Performance Computing facility.