EC-13. Ab Initio calculations of the Hg-I bond strength and its atmospheric relevance

Abstract
Mercury is a neurotoxin that poses a health risk, in particular for pregnant women. The atmospheric oxidation of gaseous elemental mercury (GEM) is the primary source of gaseous oxidized mercury (GOM) that deposits to ecosystem and can bioaccumulate as part of the food chain. The importance of iodine as oxidant of GEM has traditionally been dismissed, due to low iodine concentrations and faster Hg-I adduct decomposition rates (compared to more stable Hg-Br and Hg-OH adducts). Here we revisit theoretically the dissociation energy of the Hg-I bond strength, with the aim of obtaining a more accurate and reliable estimate of it. We used a highly precise method, called CCSD(T), to calculate the dissociation energy of Hg-I. The calculations included corrections for core-valence interactions and the use of increasingly larger basis sets to get the most accurate value possible. We also accounted for scalar relativity and spin-orbit coupling interactions. The atmospheric implications for mercury chemistry will be discussed. References: Shepler, B. C., Balabanov, N. B., & Peterson, K. A. (2005). Ab initio thermochemistry involving heavy atoms: An investigation of the reactions Hg+ IX (X= I, Br, Cl, O). The Journal of Physical Chemistry A, 109(45), 10363-10372. Cremer, D., Kraka, E., & Filatov, M. (2008). Bonding in mercury molecules described by the normalized elimination of the small component and coupled cluster theory. ChemPhysChem, 9(17), 2510-2521.