A new accurate ground-state potential energy surface of ethylene and predictions for rotational and vibrational energy levels

Thibault Delahaye; Andrei Nikitin; Michaël Rey; Péter G Szalay; Vladimir G Tyuterev

doi:10.1063/1.4894419

A new accurate ground-state potential energy surface of ethylene and predictions for rotational and vibrational energy levels

J Chem Phys. 2014 Sep 14;141(10):104301. doi: 10.1063/1.4894419.

Authors

Thibault Delahaye¹, Andrei Nikitin², Michaël Rey¹, Péter G Szalay³, Vladimir G Tyuterev¹

Affiliations

¹ Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, F-51687, Reims Cedex 2, France.
² Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Russian Academy of Sciences, 634055 Tomsk, Russia and Quamer, State University of Tomsk, Russia.
³ Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest, Hungary.

PMID: 25217910
DOI: 10.1063/1.4894419

Abstract

In this paper we report a new ground state potential energy surface for ethylene (ethene) C2H4 obtained from extended ab initio calculations. The coupled-cluster approach with the perturbative inclusion of the connected triple excitations CCSD(T) and correlation consistent polarized valence basis set cc-pVQZ was employed for computations of electronic ground state energies. The fit of the surface included 82,542 nuclear configurations using sixth order expansion in curvilinear symmetry-adapted coordinates involving 2236 parameters. A good convergence for variationally computed vibrational levels of the C2H4 molecule was obtained with a RMS(Obs.-Calc.) deviation of 2.7 cm(-1) for fundamental bands centers and 5.9 cm(-1) for vibrational bands up to 7800 cm(-1). Large scale vibrational and rotational calculations for (12)C2H4, (13)C2H4, and (12)C2D4 isotopologues were performed using this new surface. Energy levels for J = 20 up to 6000 cm(-1) are in a good agreement with observations. This represents a considerable improvement with respect to available global predictions of vibrational levels of (13)C2H4 and (12)C2D4 and rovibrational levels of (12)C2H4.