The chemical state of Hg in synthetic crystals of zinc and mercury sulfides studied by XAFS spectroscopy

Abstract

In this study, a series of synthetic mercury-bearing sphalerite and zinc-bearing metacinnabar crystals was grown using the salt flux method at 605-650 ​°C at the hot and cold ends of the ampoule, respectively, in a composition range from 2 to 82 ​mol.% of the HgS component. According to the XAFS (X-ray Absorption Fine Structure) measurements, mercury in the sphalerite-metacinnabar crystals exists in the form of a solid solution. The EXAFS (Extended X-ray Absorption Fine Structure) spectra confirm the increase in the ionic radius of all coordination shells in the crystal structure of the Hg-sphalerite and Zn-metacinnabar on 0.14–0.28 ​Å, depending on the calculated model compared to the distances in pure sphalerite. However, the crystal structure does not change. The established nominal oxidation state of mercury in the (Zn, Hg)S is 2+.