A fully ab initio potential curve of near-spectroscopic quality for OH- ion: importance of connected quadruple excitations and scalar relativistic effects.
A benchmark study has been carried out on the ground-state potential curve of the hydroxyl anion, OH-, including detailed calibration of both the l-particle and n-particle basis sets. The CCSD(T) basis set limit overestimates omega(e) by about 10 cm(-1), which is only remedied by inclusion of connected quadruple excitations in the coupled cluster expansion--or, equivalently, the inclusion of the 2pi orbitals in the active space of a multireference calculation. Upon inclusion of scalar relativistic effects (-3 cm(-1) on omega(e)), a potential curve of spectroscopic quality (sub-cm(-1) accuracy) is obtained. Our best computed EA(OH), 1.828 eV, agrees to three decimal places with the best available experimental value. Our best computed dissociation energies, D0(OH-) = 4.7796 eV and D0(OH) = 4.4124 eV, suggest that the experimental D0(OH) = 4.392 eV may possibly be about 0.02 eV too low.
Martin
J M
JM
Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel. comartin@wicc.weizmann.ac.il
D055580:Astronomical Phenomena; D001256:Astronomy; D002138:Calibration; D019411:Clinical Laboratory Techniques; D019443:Cosmic Dust / Q000032:analysis*; D006878:Hydroxides / Q000737:chemistry*; D008956:Models, Chemical
D019443:Cosmic Dust; D006878:Hydroxides; C031356:hydroxide ion