Ab initio study of the hydration complexes of HCO−3

Abstract

Ab initio SCF-MO calculations have been performed on the first three hydrates of CHO−3 using minimal (STO-3G) and extended (4-31G) basis sets. The influence of diffuse functions (STO-3G* and 4-31G* basis sets), and the magnitude of the basis set superposition error (BSSE) have also been tested in few monohydrate complex calculations. Except for minimal basis set calculations, the computed hydration energy (ΔE0,1) associated with the first hydration step is in rather good agreement with the experimental value if the BSSE is taken into account. We also present the structures and the energies of the most stable di- and trihydrated complexes computed with the 4-31G basis set. Our results are discussed with a view to a study of the aqueous-phase reaction: CO2(aq) + OH−(aq) → HCO−3(aq).