Atomic basis sets for first-principles studies of Si nanowires

Total energy and electronic structure calculations are performed within Density Functional Theory for silicon nanowires with hydrogen and hydroxyl surface termination and for doped silicon nanowires. The performance of numerical atomic orbital basis sets on predicting the structural and electronic properties is evaluated using plane wave results as a reference. For studies of silicon nanowires, a good compromise between efficiency and accuracy is offered by optimised double zeta polarised basis sets. This set yields total energy per atom converged within 0.1. meV and band structures that compare favourably to those generated by plane waves. Using a band structure analysis, it is found that conductivity predictions are much more sensitive to the basis sets than estimates of the mean free path. Finally, optimised orbitals are transferable and can be used in more demanding realistic device simulations.