Accurate ab initio intermolecular potential energy surface for the quintet state of the O2(Σg−3)–O2(Σg−3) dimer

Abstract

A new potential energy surface ͑PES͒ for the quintet state of rigid O 2 ͑ 3 ⌺ g − ͒ +O 2 ͑ 3 ⌺ g − ͒ has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations ͓RCCSD͑T͔͒. A large number of relative orientations of the monomers ͑65͒ and intermolecular distances ͑17͒ have been considered. A spherical harmonic expansion of the interaction potential has been built from the ab initio data. It involves 29 terms, as a consequence of the large anisotropy of the interaction. The spherically averaged term agrees quite well with the one obtained from analysis of total integral cross sections. The absolute minimum of the PES corresponds to the crossed ͑D 2d ͒ structure ͑X shape͒ with an intermolecular distance of 6.224 bohrs and a well depth of 16.27 meV. Interestingly, the PES presents another ͑local͒ minimum close in energy ͑15.66 meV͒ at 6.50 bohrs and within a planar skewed geometry ͑S shape͒. We find that the origin of this second structure is due to the orientational dependence of the spin-exchange interactions which break the spin degeneracy and leads to three distinct intermolecular PESs with singlet, triplet, and quintet multiplicities. The lowest vibrational bound states of the O 2 -O 2 dimer have been obtained and it is found that they reflect the above mentioned topological features of the PES: The first allowed bound state for the 16 O isotope has an X structure but the next state is just 0.12 meV higher in energy and exhibits an S shape.

Diatom–diatom interactions: Building potential energy surfaces and effect of intramolecular vibrations

“…We show that the main anisotropy term ( f 202 ) can be obtained with the same degree of accuracy than the isotropic one, also starting from the calculations at the KK geometries. The approach is tested for the O 2 ( 3 Σ)O 2 ( 3 Σ) dimer for which an accurate PES has been published 12. In that work, the dependence of the interaction with the intermolecular degrees of freedom was computed for the state of quintet multiplicity using restricted coupled‐cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)].…”

Influence of external electric fields on oxygen vacancies at the anatase (101) surface

“…This dimer has been the subject of detailed crossed molecular beam studies 11,12 and high resolution spectroscopy 13,14 together with accurate ab initio studies. [15][16][17] It is interesting to point out there is still controversy regarding the exact estimate of the binding energy for the dimer. 18 Even though oxygen is the third most abundant element in the universe, a large fraction of it remains unaccounted for at higher densities corresponding to the interstellar medium (ISM).…”

Molecular Interactions for Modeling of Oxygen System Using van der Waals Density Functional Approach

“…6, we present J as a functions of θ at d = 3.3Å using vdW-DF-GC. To check the accuracy of vdW-DF-GC approach, our result is compared with the Bartolomei's result of RCCSD(T) method [14]. Both curves have a very similar behavior with respect to θ except for scale of interaction energy.…”

“…Usefully, the various configurations (S-type, T-type, and X-type) are investigated, because such configurations are found in the solid oxygens at high pressures or high magnetic fields and, in the liquid oxygens [10]. The results of quantum chemistry have been already reported [11][12][13][14]. For checking accuracy of functionals, it is important to investigate other configurations using vdW-DF-GC method.…”