Hg + Br → Hg Br recombination and collision-induced dissociation dynamics

Abstract

A global potential energy surface has been constructed for the system HgBr+Ar-->Hg+Br+Ar to determine temperature dependent rate constants for the collision-induced dissociation (CID) and recombination of Hg and Br atoms. The surface was decomposed using a many-body expansion. Accurate two-body potentials for HgBr, HgAr, and ArBr were calculated using coupled cluster theory with single and double excitations and a perturbative treatment of triple excitations [CCSD(T)], as well as the multireference averaged coupled pair functional method. Correlation consistent basis sets were used to extrapolate to the complete basis set limit and corrections were included to account for scalar and spin-orbit relativistic effects, core-valence correlation, and the Lamb shift. The three-body potential was computed with the CCSD(T) method and triple-zeta quality basis sets. Quasiclassical trajectories using the final analytical potential surface were directly carried out on the CID of HgBr by Ar for a large sampling of initial rotational, vibrational, and collision energies. The recombination rate of Hg and Br atoms is a likely first step in mercury depletion events that have been observed in the Arctic troposphere during polar sunrise. The effective second order rate constant for this process was determined in this work from the calculated CID rate as a function of temperature using the principle of detailed balance, which resulted in k(T) = 1.2 x 10(-12) cm(3) molecule(-1) s(-1) at 260 K and 1 bar pressure.

How Elementary Mercury Reacts in the Presence of Halogen Radicals and/or Halogen Anions: A DFT Investigation

“…b) Ozone mixing ratio in the atmosphere (35 cm above the surface) and in the air of snow obtained at Alert, Canada (828N) from February 29th to March 9th during twilight conditions. The same decreasing trend can be observed before (10-28 February) and after (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) March) this period. Data are extracted from ref.…”

“…[18][19][20][21][22] However, Tossel [23] reported a theoretical investigation of the thermal formation of Hg II complexes in the presence of various radicals. Balabanov et al [24][25][26] also reported dynamical studies on the collision of mercury atoms with halogen molecules. Theoretical methods, and in particular DFT methods, have proven in the past their ability in predicting the reactivity of metallic complexes.…”

Recent Advances in Atmospheric Chemistry of Mercury

“…Previous laboratory studies reported apparent rate coefficients in the range of (3.6 ± 0.9) × 10 −13 to (3.2 ± 0.3) × 10 −12 cm 3 molec −1 s −1 , at 1 atm and 298 K [19,20,22]. Theoretical studies estimated the rate constants to be from 9.8 × 10 −13 to 2.1 × 10 −12 cm 3 molec −1 s −1 , at 1 atm and 298 K [3,21,23]. Theoretical and experimental rate constants for mercury oxidation by Br and Cl atoms at 298 K have previously been compared in detail in Table A.2 by Subir et al [18].…”

Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory

“…There have been several quantum chemical studies of mercury compounds, [18,19, where those of the Peterson group [18,[21][22][23][24][25][26][27][28] and those by Tossell [29][30][31][32][33] are most noteworthy. Each of these investigations focused on selected mercury compounds HgX; however none of them attempted a comprehensive study of mercury bonding by varying X systematically within the periodic table.…”

“…However this reaction sequence can be excluded on the basis of theoretical calculations carried out herein and in the studies of others. [18][19][20][21][22][23][24][25][26][27][28][29][30] The reaction of elemental Hg with OH radicals is more likely considering a reaction energy of 12 kcal mol…”