First principle conductance calculation of zigzag, armchair and mixed geometries of S–6C–4H–S structures

We investigated ballistic transport properties of armchair (AC), zigzag (ZZ), mixed, rotated-AC and rotated-ZZ geometries of small molecules made of 2S, 6C & 4H atoms which exhibit sp–sp2 hybridization. Well-tested first principle scattering states formalism implemented in Quantum Espresso package has been employed to perform the calculations. The chains made of 6C-atoms with 1S-atom at each end and 4H-atoms attached to different C-atoms have been relaxed. This resulted in AC, ZZ, mixed geometry structures. Differences in transmission coefficient (T) curves of AC, ZZ and mixed molecules suggest geometry dependence of conductance and are in accordance with the previously reported results for AC and ZZ nanoribbons. In addition, our computed results for rotated-AC and rotated-ZZ suggest that the angle between electrode surface layers and molecular axis plays dominant role, compared to the role of angle between S–C bond and electrode surface layers, in determining conduction through the structure. The structures with molecular axis perpendicular to electrode surface layers yield higher conductance values.