Electronic structure, galvanomagnetic and magnetic properties of the bismuth subhalides Bi4I4 and Bi4Br4

Two bismuth-rich subhalides, Bi₄Br₄ and Bi₄I₄, featuring extended quasi one-dimensional metallic fragments in their structures, have been investigated. The gas-phase technique of crystal growth has been refined for obtaining large (up to 5 mm long) single crystals. Electronic structure calculations on three-dimensional structures of both compounds have been performed (DFT level, hybrid B3LYP functional), predicting a semiconducting behavior for both compounds, with an indication of possible directional anisotropy of electric conductivity. Galvanomagnetic (resistance, magnetoresistance, Hall effect, thermopower) and magnetic (temperature and field dependence of magnetization) properties have been measured experimentally. Both compounds are found to be diamagnetic, room-temperature semiconductors with n-type conductivity. While Bi₄Br₄ demonstrates a typical case of one dimensionality, the difference in magnetoresistivity between Bi₄Br₄ and Bi₄I₄ indicates some weak interactions between isolated bismuth metallic fragments within the bismuth substructures.