On the use of explicitly correlated treatment methods for the generation of accurate polyatomic -He/H2 interaction potential energy surfaces: The case of C3-He complex and generalization

M M Al Mogren; O Denis-Alpizar; D Ben  Abdallah; T Stoecklin; P Halvick; M-L Senent; M Hochlaf

doi:10.1063/1.4890729

On the use of explicitly correlated treatment methods for the generation of accurate polyatomic -He/H2 interaction potential energy surfaces: The case of C3-He complex and generalization

J Chem Phys. 2014 Jul 28;141(4):044308. doi: 10.1063/1.4890729.

Authors

M M Al Mogren¹, O Denis-Alpizar², D Ben Abdallah³, T Stoecklin², P Halvick², M-L Senent⁴, M Hochlaf⁵

Affiliations

¹ Chemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Kingdom of Saudi Arabia.
² Université de Bordeaux, ISM, CNRS UMR 5255, 33405 Talence Cedex, France.
³ Laboratoire de Spectroscopie Atomique, Moléculaire et Applications - LSAMA Université de Tunis, Tunis, Tunisia and Department of General Studies, Riyadh Corporation of Technology, Technical and Vocational Training Corporation, P.O. Box: 42826, Riyadh 11551, Kingdom of Saudi Arabia.
⁴ Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-C.S.I.C., Serrano 121, Madrid 28006, Spain.
⁵ Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France.

PMID: 25084911
DOI: 10.1063/1.4890729

Abstract

Through the study of the C3(X1Σg (+)) (1)Σg (+)) + He((1)S) astrophysical relevant system using standard (CCSD(T)) and explicitly correlated (CCSD(T)-F12) coupled cluster approaches, we show that the CCSD(T)-F12/aug-cc-pVTZ level represents a good compromise between accuracy and low computational cost for the generation of multi-dimensional potential energy surfaces (PESs) over both intra- and inter-monomer degrees of freedom. Indeed, the CCSD(T)-F12/aug-cc-pVTZ 2D-PES for linear C3 and the CCSD(T)-F12/aug-cc-pVTZ 4D-PES for bent C3 configurations gently approach those mapped at the CCSD(T)/aug-cc-pVXZ (X = T,Q) + bond functions level, whereas a strong reduction of computational effort is observed. After exact dynamical computations, the pattern of the rovibrational levels of the intermediate C3-He complex and the rotational and rovibrational (de-) excitation of C3 by He derived using both sets of PESs agree quite well. Since C3 shows a floppy character, the interaction PES is defined in four dimensions to obtain realistic collisional parameters. The C-C-C bending mode, which fundamental lies at 63 cm(-1) and can be excited at very low temperatures is explicitly considered as independent coordinate. Our work suggests hence that CCSD(T)-F12/aug-cc-pVTZ methodology is the key method for the generation of accurate polyatomic - He/H2 multi-dimensional PESs.