Computation of Rate Constants for Some Chlorination Reactions of Mercury Atoms during Combustion

The geometric optimizations of reactants, products and transition states have been made using the quantum chemistry MP2 method at the SDD/6-311 + + G(3df, 3pd) basis function levels. The properties of stable minima were validated by analysis of vibration frequencies. Furthermore, the microscopic reaction mechanisms have been investigated by ab initio calculations. Among those chlorination reactions involving mercury, the processes of the reaction Hg + HCl → HgCl + H are Hg + HCl → TS(HgClH) → HgCl + H, which include only one transition state (TS) and no intermediate (M), which is similar in character to the reactions HgCl + HCl → HgCl₂ + H and HgCl + Cl → HgCl₂. On the basis of the geometric optimization, the rate constants at every 1 degree interval from 200 K to 2000 K were calculated neither from experimental data nor by estimation, but directly from the quantum chemistry software ‘Khimera’.