Ab initio and scaled potential energy surfaces for Ar–C2H2: Comparison with scattering and spectroscopic experiments

Abstract

Articles you may be interested inThe intermolecular potential energy surface for CO2-Ar: Fitting to highresolution spectroscopy of Van der Waals complexes and second virial coefficients Vibration-rotation excitation of CO by hot hydrogen atoms: Comparison of two potential energy surfaces Ab initio studies on the interstellar molecules C3H2 and C3H and the mechanism for the neutral-neutral reaction C(3 P)+C2H2New coupled-cluster ab initio potential energy surfaces ͑PES's͒ were determined for the interaction of Ar with a rigid acetylene molecule. These PES's were in addition modified by scaling the correlation energy. Based on both the original and scaled PES's, close-coupled calculations of the total differential scattering cross section were carried out. Rovibrational energy levels of the Ar-C 2 H 2 complex were computed variationally. In addition, we simulated the ir spectra corresponding to excitation of the upper diad of the 3 / 2 ϩ 4 ϩ 5 excited molecular vibrational states. The comparison of all these quantities with experiment shows generally good agreement for the several scaled PES's. In addition, the sensitivity of the PES to the experimental data are investigated by varying the scaling factor. The original and scaled PES's are also compared with several phenomenological PES's and a previously published ab initio PES ͓F.-M.

Intermolecular interaction potentials for the Ar–C2H2, Kr–C2H2, and Xe–C2H2 weakly bound complexes: Information from molecular beam scattering, pressure broadening coefficients, and rovibrational spectroscopy

“…Herein, we decided to compare our results with experimental ones and with values obtained from other empirical or semiempirical PES, considering that an exhaustive discussion of the theoretical works has been presented in Ref. 21. We stress that at variance with the other studies our PES has not been fitted to the spectroscopic data.…”

“…The opportunity of such an amount of experimental information has stimulated the production of a large number of PESs obtained either phenomenologically by fitting a selected set of experimental observables 9,12,17,18 or from direct ab initio calculations at various level of sophistication. [19][20][21][22][23] The anisotropy of the PES is stronger for the Ar case with respect to those shown by the lighter rare gas complexes, even if somewhat elusive. 19 Anyway, the rotational spectrum of Ar-C 2 H 2 is drastically different from that of Ne-C 2 H 2 ; 4 and despite the large amplitude internal motions of the system, it has been described with a semirigid rotor Hamiltonian.…”

Experimental 2CH excitation in acetylene-containing van der Waals complexes

“…C 2 H 2 -Ar presents a so-called pathologically flat potential energy surface, which has been extensively investigated by ab initio calculations [40,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66], demonstrating the skew T-shaped equilibrium geometry, with e ¼ 60…”

A Critical Assessment of Coupled Cluster Method in Quantum Chemistry

“…In cases where only derived properties are experimentally accessible (say, scattering cross sections or infrared spectra), even a simple scaling of theoretical correlation energies can help to produce the desired PESs, allowing a better interpretation of experimental results. (Cf., e.g., [378]. )…”

“…The shortcomings of theoretical PESs (due to both basis-set limitations and higher order excitations) can be partially compensated for by scaling of computed correlation energy contributions, as suggested by Yang et al [378] in their study of the Ar-ClH2 system. Since the entire PES is required here, it i s not surprising that the best results were obtained with the appropriately scaled CCSD PES, even though the results based on the CCSD(T) PES were only slightly less accurate.…”