Characterization of the structure and dynamics of an aqueous Hg 2+ solution by an ab initio molecular dynamics study

Abstract

Quantum mechanical charge field (QMCF) MD simulation has been performed to investigate the structure and dynamics of Hg 2+ hydrate. The first-shell hexacoordinated [Hg(H 2O) 6] 2+ complex with an average Hg 2+-O distance of 2.40 Å is dominantly found, which corresponds to the neutron diffraction and extended X-ray absorption fine structure (EXAFS) experiments. Other species, in particular the 7-fold coordinated complexes, can be formed transiently, according to the water exchange processes with an associative interchange ( I a) mechanism. The second hydration shell exhibits a Hg 2+-O distance of 4.6 Å with a coordination number of ~ 14. The mean residence times (MRTs) of first- and second-shell waters clearly indicate a strong “structure-forming” ability of Hg 2+ in aqueous solution.