Atomic basis sets for first-principles studies of Si nanowires

► DFT benchmarks using numerical atomic orbitals for Si nanowire properties. ► Optimised double zeta polarised basis set offers relatively converged results. ► Inclusion of d-polarization functions is crucial for correct results. ► Transferable optimised NAOs can be used in realistic device simulations. ► Conductivity is more sensitive to the basis sets than mean-free-path estimates.