Fig. 2: HMS formation under acidic conditions.
a A representative mechanism for HCHO + \({{{{\rm{HOSO}}}}}_{2}^{-}\) reaction. b Gibbs free-energy profiles for HCHO + \({{{{\rm{HOSO}}}}}_{2}^{-}\) reaction in gas phase and their corresponding structures of the stationary points optimized at M06-2x/6-311++G(d, p) level of theory. Relative single point energies of reactant complex (R), transition state (TS), and product (P) were obtained at CCSD(T)/aug-cc-pVTZ level of theory. c (Top) Schematic representation of the CV. (Bottom) Gibbs free-energy profile (blue line) with error band (shaded area) for aqueous HCHO + \({{{{\rm{HOSO}}}}}_{2}^{-}\) reaction compared with the experimental result (\(\Delta {G}_{\exp }^{{{\ddagger}} }\)) of Boyce et al.35. Relevant error band is calculated on the standard deviation by employing cubic interpolation on three independently obtained free-energy profiles. The error of the free-energy barrier is the standard deviation of the free-energy barriers of three metadynamics simulations. d (Top) Snapshot structures (reactant, Rbulk, transition state, TSbulk, and product, Pbulk) obtained from a single metadynamics-biased AIMD simulations. (Bottom) Relevant CV variation as a function of the simulation time for aqueous reaction (blue line). e Gibbs free-energy profile (red line) with error band (shaded area) for the heterogeneous HCHO + \({{{{\rm{HOSO}}}}}_{2}^{-}\) reaction. Calculation of error band is same as the bulk reaction simulation. f (Top) Snapshot structures (Rinter, TSinter, and Pinter) obtained from a single metadynamics-biased AIMD simulations. (Bottom) Relevant CV variation as a function of the simulation time for interfacial reaction (red line).
