Isotopic effects on the rotational (de-)excitation rate coefficients of ortho-CH3Cl colliding with He.

Chloromethane, CH3Cl, is the first organohalogen molecule to be detected in the interstellar medium. Using the recently generated accurate three-dimensional potential energy surface (3D-PES) for the weakly bound CH335Cl-He complex, we deduced that of CH337Cl-He. Both 3D-PESs were incorporated later into dynamical computations code for nuclear motions treatments of each isotopologue colliding with He.

Towards the generation of potential energy surfaces of weakly bound medium-sized molecular systems: the case of benzonitrile-He complex.

Currently, the explicitly correlated coupled cluster method is used routinely to generate the multi-dimensional potential energy surfaces (mD-PESs) of van der Waals complexes of small molecular systems relevant for atmospheric, astrophysical and industrial applications. Although very accurate, this method is computationally prohibitive for medium and large molecules containing clusters. For instance, the recent detections of complex organic molecules (COMs) in the interstellar medium, such as benzonitrile, revealed the need to establish an accurate enough electronic structure approach to map the mD-PESs of these species interacting with the surrounding gases.

Theoretical study of the CO-O van der Waals complex: potential energy surface and applications.

A four-dimensional-potential energy surface (4D-PES) of the atmospherically relevant carbon dioxide-oxygen molecule (CO-O) van der Waals complex is mapped using the explicitly correlated coupled cluster method with single, double, and perturbative triple excitations (UCCSD(T)-F12b), and extrapolation to the complete basis set (CBS) limit using the cc-pVTZ-F12/cc-pVQZ-F12 bases and the formula. An analytic representation of the 4D-PES was fitted using the method of interpolating moving least squares (IMLS). These calculations predict that the most stable configuration of CO-O complex corresponds to a planar slipped-parallel structure with a binding energy of ∼ -243 cm.

Potential energy surface of the CO2-N2 van der Waals complex.

Four-dimensional potential energy surface (4D-PES) of the atmospherically relevant CO2-N2 van der Waals complex is generated using the explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in conjunction with the augmented correlation consistent triple zeta (aug-cc-pVTZ) basis set. This 4D-PES is mapped along the intermonomer coordinates. An analytic fit of this 4D-PES is performed.

Explicit correlation treatment of the potential energy surface of CO2 dimer.

We present an extensive study of the four-dimensional potential energy surface (4D-PES) of the carbon dioxide dimer, (CO2)2. This PES is developed over the set of intermolecular coordinates. The electronic computations are carried out at the explicitly correlated coupled cluster method with single, double, and perturbative triple excitations [CCSD(T)-F12] level of theory in connection with the augmented correlation-consistent aug-cc-pVTZ basis set.

On the accuracy of explicitly correlated methods to generate potential energy surfaces for scattering calculations and clustering: application to the HCl-He complex.

We closely compare the accuracy of multidimensional potential energy surfaces (PESs) generated by the recently developed explicitly correlated coupled cluster (CCSD(T)-F12) methods in connection with the cc-pVXZ-F12 (X = D, T) and aug-cc-pVTZ basis sets and those deduced using the well-established orbital-based coupled cluster techniques employing correlation consistent atomic basis sets (aug-cc-pVXZ, X = T, Q, 5) and extrapolated to the complete basis set (CBS) limit. This work is performed on the benchmark rare gas-hydrogen halide interaction (HCl-He) system. These PESs are then incorporated into quantum close-coupling scattering dynamical calculations in order to check the impact of the accuracy of the PES on the scattering calculations.