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

Abstract

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. For this system, we deduced inelastic collisional data including (de-)excitation collisional and pressure broadening cross sections. Our work shows that the CCSD(T)-F12/aug-cc-pVTZ PES describes correctly the repulsive wall, the van der Waals minimum and long range internuclear distances whereas cc-pVXZ-F12 (X = D,T) basis sets are not diffuse enough for that purposes. Interestingly, the collision cross sections deduced from the CCSD(T)-F12/aug-cc-pVTZ PES are in excellent agreement with those obtained with CCSD(T)/CBS methodology. The position of the resonances and the general shape of these cross sections almost coincide. Since the cost of the electronic structure computations is reduced by several orders of magnitude when using CCSD(T)-F12/aug-cc-pVTZ compared to CCSD(T)/CBS methodology, this approach can be recommended as an alternative for generation of PESs of molecular clusters and for the interpretation of accurate scattering experiments as well as for a wide production of collisional data to be included in astrophysical and atmospherical models.

Potential energy surface of the CO2–N2 van der Waals complex

“…We can conclude that the CCSD(T)-F12a/aug-cc-pVTZ method performs very well for selected configurations at long-range separations which confirms again the validity of this methodology. 15,43,17 …”

“…We established also that this level of theory is suited to generate accurate multidimensional PESs of weakly bound dimers with reduced computational cost. [12][13][14][15][16][17] At present, we take advantage of this technique to derive the 4D-PES of the CO 2 -N 2 complex along the intermonomer coordinates. Later on, we deduced an analytical representation of this 4D-PES.…”

Rotational study of the NH3–CO complex: Millimeter-wave measurements and ab initio calculations

“…We also show the results obtained at the explicitly correlated CCSD(T)-F12a 20 and a medium-sized basis set. It was previously shown [21][22][23] that the CCSD(T)-F12 method can provide accurate spectroscopic data for bimolecular complexes. It is seen in Fig.…”

Theoretical spectroscopic characterization at low temperatures of detectable sulfur-organic compounds: Ethyl mercaptan and dimethyl sulfide

“…59 As it is well established in the literature, the CCSD(T)-F12/VTZ-F12 level of theory reaches the standard CCSD(T)/AV5Z accuracy, with a strong reduction of computational efforts by about two orders of magnitude in CPU time and disk. [61][62][63][64][65][66] Note that the explicitly correlated coupled-cluster methodology presently used in conjunction with the VTZ-F12 basis set allows to describe the correlation effects due to valence electrons.…”