LiHgTeO3: a Hg(I)-containing tellurite crystal with typical Hg-Hg bonds.

Birefringent crystals have attracted considerable attention owing to their unique capability in laser polarization modulation. Recently, Hg(I) ions featuring Hg-Hg bonds have been demonstrated to make a significant contribution to enhancing birefringence. Herein, we focused on the rarely investigated mercury-based tellurite system and successfully synthesized a novel Hg(I)-containing tellurite crystal, LiHgTeO3, featuring typical Hg-Hg bonds. This compound exhibits moderate birefringence (0.064 at 546 nm), a band gap of 3.05 eV, and high thermal stability up to 300 °C. Theoretical calculations reveal that the synergistic effect of [TeO3]2- polyhedra with stereochemically active lone pairs and the [Hg2O4]6- unit contributes significantly to the optical properties of the crystal. This work enriches the family of Hg(I)-based tellurite compounds.