Centrifugal distortions in molecules: An ab initio approach with application to ozone

Abstract

Our procedure for employing analytical gradients of ab initio potential energy hypersurfaces in the description of centrifugally distorted molecules is applied for the first time to an asymmetric top, namely ozone. Both single determinantal (HF/6-31G*) and analytically fitted multiconfigurational self-consistent field surfaces were utilized. The focus of the HF/6-31G* study is upon the centrifugal distortion pathway. Quartic centrifugal spectroscopic coefficients are obtained in both cases and are in reasonable agreement with experiment.

Centrifugal distortions in molecules: An ab initio approach with application to water

“…[4-101 that the representation of the dependence of the rotational energy upon the angular momentum in terms of Pad6 approximants provides much better spectral fits than the conventional power series representation that is often divergent or poorly convergent. We noted earlier [ 1,2] an approximately linear fall-off of our computed quartic centrifugal distortion coefficients with increasing angular momentum, this fall-off not matching the quadratic fall-off expected from the next (sextic) term in a power series representation. We demonstrate here the compatibility of an approximate linear fall-off to a Pade representation, thus providing further support for their use in spectral fittings.…”

“…We note, as we did for ozone [2], that the bond lengthening is roughly isotropic when expressed in terms of rotational energy rather than angular momentum. (Table I) (12) where H, is the quartic Hamiltonian, such as that from (9), and H6 is the analogous [ 161 sextic Hamiltonian.…”

“…Particularly satisfying was the excellent description of both the scalar and tensor quartic coefficients, D, and D,, respectively, for the spherical tops CH, and SF,. In a second article [2] we outlined an extension of the method to asymmetric tops and gave results for a particularly important molecule, namely ozone, for which we have also made a theoretical study of the effects of anharmonicity on its ultraviolet continuum band shape [3]. In the present article we explore two additional questions about centrifugal distortions, namely what are the effects of electron correlation on the centrifugal stabilization energies, and what is the significance of the approximately linear fall-off of effective quartic spectroscopic constants as observed in our earlier computations [ 1,2]?…”

“…Particularly satisfying was the excellent description of both the scalar and tensor quartic coefficients, D, and D,, respectively, for the spherical tops CH, and SF,. In a second article [2] we outlined an extension of the method to asymmetric tops and gave results for a particularly important molecule, namely ozone, for which we have also made a theoretical study of the effects of anharmonicity on its ultraviolet continuum band shape [3]. [4-101 that the representation of the dependence of the rotational energy upon the angular momentum in terms of Pad6 approximants provides much better spectral fits than the conventional power series representation that is often divergent or poorly convergent.…”

Turning point surfaces and their enclosed volumes for rotating Lennard-Jones rare-gas trimers ArxNe3-x,x= 0–3

“…Minimized total energy (equation(3)) versus square of the angular momentum normal to molecular plane for ArNe2. The structures are an acute isosceles triangle with Czv symmetry (o), centrosymmetric linear Ne-Ar-Ne with DWh symmetry (n), and non-centrosymmetric Ar-Ne-Ne with C, , symmetry (A).…”