First principle calculations of conductance within plane wave basis set via nonorthogonal Wannier-type atomic orbitals

Abstract

We present a plane wave/pseudopotential implementation of the method to calculate electron transport properties of nanostructures. The conductance is calculated via the Landauer formula within formalism of Green's functions. Nonorthogonal Wannier-type atomic orbitals are obtained by the sequential unitary rotations of virtual and occupied Kohn-Sham orbitals, which is followed by two-step variational localization. We use these non-orthogonal Wannier type atomic orbitals to partition the Kohn-Sham Hamiltonian into electrode-contact-electrode submatrices. The electrode parts of the system are modeled by two metal clusters with additional Lorentzian broadening of discrete energy levels. We examined our implementation by modeling the transport properties of Na atomic wires. Our results indicate that with the appropriate level broadening the small cluster model for contacts reproduces odd-even oscillations of the conductance as a function of the nanowire length.