Spin polarised density functional theory (DFT) calculations were performed in this work with the Vienna Ab initio Simulation Package (VASP), using the Perdew-Burke Ernzerhof (PBE) exchange-correlation functional . Projector-augmented wave (PAW) pseudopotentials were used for all species . Two sets of pseudopotentials were used throughout this work. For the convex hull analysis of LaxPr4-xNi3O10 structures, a softer set of PAW pseudopotentials was used, labelled La, Pr_3, Ni, and O_s in the VASP 5 distribution, using a plane wave cut off of 400 eV. For the calculation of structural properties, defect formation energies and activation energies, p valence electrons were included for Ni (Ni_pv) and the normal oxygen pseudopotential (O) was used. For this later pseudopotential set, a plane wave cut off of 520 eV was used. An electronic convergence of 1×10 -6 eV was used for all calculations. A Hubbard U parameter was added to Ni using the rotationally invariant approach of Dudarev et al., to improve the description of electron correlation 29 . A U value of 6.2 eV was used for Ni based on the previous work by Wang et al . Gamma centred k-point meshes were used for all calculations to sample the Brillouin zone with a k-point grid density of at least 20 Å. A collinear ferromagnetic spin alignment was used for all calculations in this study.