β-Technetium dichloride: solid-state modulated structure, electronic structure, and physical properties.

Area of Science:

• Solid-state chemistry
• Inorganic materials science
• Materials characterization

Background:

• Technetium dichloride (TcCl2) exists in multiple forms, influencing its properties.
• Understanding polymorphs is crucial for materials development and application.

Purpose of the Study:

• Synthesize and characterize a new polymorph of technetium dichloride, β-TcCl2.
• Investigate the crystallographic structure and physical properties of β-TcCl2.
• Explore potential stable forms of TcCl2 using theoretical calculations.

Main Methods:

• Synthesis of β-TcCl2 via reaction of Tc metal and chlorine at 450 °C in a sealed tube.
• Crystallographic structure determination.
• Physical property measurements including resistivity, Seebeck effect, magnetic susceptibility, and reflectance spectroscopy.
• Density functional theory (DFT) calculations.

Main Results:

• Successful synthesis of a new technetium dichloride polymorph, β-TcCl2.
• Elucidation of the crystal structure as infinite chains of face-sharing [Tc2Cl8] units with ordered Tc≡Tc vectors.
• β-TcCl2 identified as a p-type semiconductor with a band gap of 0.12(2) eV.
• Magnetic susceptibility measurements indicated diamagnetic behavior.

Conclusions:

• The novel β-TcCl2 polymorph possesses a unique modulated structure.
• β-TcCl2 exhibits semiconductor properties relevant for electronic applications.
• Theoretical calculations provide insights into other potential stable TcCl2 forms.