| Sumario: | A second polymorph of technetium dichloride, β-TcCl, has been synthesized from the reaction of Tc metal and chlorine in a sealed tube at 450 °C. The crystallographic structure and physical properties of β-TcCl have been investigated. The structure of β-TcCl consists of infinite chains of face sharing [TcCl] units; within a chain, the Tc≡Tc vectors of two adjacent [TcCl] units are ordered in the long-range where perpendicular and/or parallel arrangement of Tc≡Tc vectors yields a modulated structure. Resistivity and Seebeck measurements performed on a β-TcCl single crystal indicate the compound to be a p-type semiconductor while a magnetic susceptibility measurement shows technetium dichloride to be diamagnetic. A band gap of 0.12(2) eV was determined by reflectance spectroscopy measurements. Theoretical calculations at the density functional level were utilized for the investigation of other possible stable forms of TcCl.
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