Growth, structure and optical properties of Tl4HgBr6 single crystals

Experimental and theoretical study of Raman scattering spectra of ternary chalcogenides Tl4HgI6, Tl4HgBr6, and TlHgCl3

“…All compounds under investigation are direct band gap semiconductors and reveal a pronounced anisotropy in crystallographic directions that are parallel or perpendicular to the c ‐axis. The band gap values for Tl 4 HgI 6 , Tl 4 HgBr 6, and TlHgCl 3 are found to be 2.15, 2.43, and 2.74 eV, respectively …”

“…The Bridgman–Stockbarger method was used to grow Tl 4 HgI 6 and Tl 4 HgBr 6 crystals. Initial mixture in all cases consisted of binary halogenides that were obtained and purified using a technique similar to our previous research . Because of the incongruent melting type for Tl 4 HgBr 6 , the composition of the starting material for the growth was selected from its primary crystallization field and amounted to 70 mol.% TlBr and 30 mol.% HgBr 2 , in which the excessive HgBr 2 was used as a solvent.…”

“…The samples cut of them for Raman measurements were 0.5 × 0.5 × 0.2 cm. A more detailed description of the crystal growth process and X‐ray diffraction characterization is given in our previous works …”

“…It was recently shown that ternary chalcogenides Tl 4 HgI 6 and Tl 4 HgBr 6 possess attractive physical properties . In particular, high atomic numbers Z of the constituents (Tl: 81, Hg: 80, I: 53, and Br: 35) result in rather high material densities of 6.719 and 6.558 g/сm 3 , respectively .…”

“…Tl 4 HgBr 6 was initially found to be isomorphic to Tl 4 HgI 6 and belonging to the centrosymmetric P 4/mnc space group . Later, however, both compounds were considered to be non‐centrosymmetric (P 4nc ) . The structure of TlHgCl 3 was found to be orthorhombic P mna …”