TITLE

Post-Hartree–Fock study on Ar–HCO+ and He–HCO+ complexes: A critical examination of experimental data

AUTHOR(S)
Nowek, Andrzej; Leszczynski, Jerzy
PUB. DATE
October 1996
SOURCE
Journal of Chemical Physics;10/15/1996, Vol. 105 Issue 15, p6388
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The second order Mo\ller–Plesset (MP2) to the fourth order many-body perturbation theory including single, double, triple, and quadruple substitutions (MP4(SDTQ)), coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], quadratic configuration interaction with single and double substitutions (QCISD), and QCISD including noniterative triples contributions [QCISD(T)] ab initio correlated levels of theory have been employed in studies on molecular geometry and stability of the Ar–HCO+ and He–HCO+ complexes. Triple-zeta split-valence (6-311G) and correlation consistent (cc-pVTZ) basis sets augmented with diffuse and polarization functions were used. At applied levels of theory the predicted interaction energies (corrected for the basis set superposition error and zero-point vibrational energy) for Ar–HCO+ range from -3.21 kcal/mol (QCISD/6-311G(2df,2pd) to -4.21 kcal/mol (MP4(SDTQ)/aug-cc-pVTZ), and for He–HCO+ vary from -0.12 kcal/mol (-42 cm-1, MP2/cc-pVTZ) to -0.37 kcal/mol (-130 cm-1, CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVTZ). The optimized Ar–H distance (2.1392 Å at QCISD/cc-pVTZ and 2.1222 Å at MP2/aug-cc-pVTZ) agrees very well with the experimentally determined (2.13 Å) value, whereas when step-by-step higher level methods and basis sets are applied, the predicted He–H distance (1.9156 Å at QCISD(T)/aug-cc-pVTZ dramatically retreats from the experimental value of 2.00 Å. © 1996 American Institute of Physics.
ACCESSION #
7649542

 

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