Accurate Calculations of Rate Constants for the Forward and Reverse H2O + CO ⇆ HCOOH Reactions

The forward and reverse H2O + CO <-> HCOOH reactions were investigated using high-level methodologies in order to provide accurate thermodynamic and kinetic data between 200 and 4000K. Geometries of reactants, transition state (TS), and product were determined with the Coupled Cluster Theory including single and double excitations (CCSD) along with the cc-pVTZ basis set, whereas associated vibrational frequencies, zero-point energies, and thermal corrections were scaled to consider anharmonicity effects. Besides, the description of electronic energies was improved by means of core-valence correlation and iterative triple-excitation contributions together with a complete basis set extrapolation (E-CBS,E-Delta) in order to achieve accurate values of enthalpies, Gibbs energies, and rate constants. Such rate constants were estimated at the high-pressure limit by variational TS treatments combined with different quantum tunneling approaches. Finally, modified Arrhenius' equations were fitted between 700 and 4000K from our most reliable results.