Compositional ordering and quantum transport in Mo₆S_9−xI_x nanowires: Ab initio calculations

We use ab initio calculations to study the compositional ordering and quantum transport in Mo₆S_9−xI_x 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.