Compositional ordering and quantum transport in Mo6S9−xIx nanowires: Ab initio calculations

We use ab initio calculations to study the compositional ordering and quantum transport in Mo6S9−xIx nanowires. The skeleton of these nanowires consists of Mo octahedra, which are functionalized by S and I adsorbates and connected by flexible S3 bridges. The optimum geometries and relative stabilities at different compositions are determined by using density functional theory. We find nanowires with x=3 to be particularly stable. Nanowires with other compositions are likely to phase separate into iodine-rich and iodine-depleted domains, some of which should have the Mo6S6I3 stoichiometry. Our transport calculations, which are based on the nonequilibrium Green’s function formalism, indicate that the nanowires are metallic independent of composition and exhibit a quantum conductance of G=3G0, with the three conductance channels involving the S3 bridges.