The SiOH+–HSiO+ system: A high level ab initio quantum mechanical study

Abstract

Ab initio electronic structure theory has been employed in order to investigate the ground state potential energy hypersurface of the SiOH+–HSiO+ system. Geometries and physical properties including dipole moments, harmonic vibrational frequencies, and infrared intensities of two equilibrium and isomerization (1,2 hydrogen shift) reaction transition state were determined. The self-consistent-field, configuration interaction with single and double excitations, coupled cluster with single and double excitations (CCSD), and CCSD with perturbative triple excitations [CCSD(T)] levels of theory were used with five basis sets. At the highest level of theory employed in this study, CCSD(T) using the triple zeta plus double polarization with diffuse and higher angular momentum functions basis set, linear SiOH+ is predicted to be more stable than linear HSiO+ by 66.1 kcal/mol. This energy difference becomes 64.1 kcal/mol with an appropriate zero-point vibrational energy (ZPVE) correction. At the same level of theory, the classical barrier height for the exothermic isomerization (1,2 hydrogen shift) reaction HSiO+→SiOH+ is determined to be 29.3 kcal/mol and the activation energy (with the ZPVE correction) is 27.3 kcal/mol. The geometrical and energetic features are compared with those of the valence isoelectronic HBO–BOH, HCO+–COH+, and AlOH–HAlO systems.