A new full-dimensional ab initio intermolecular potential energy surface and vibrational states for (HF)2 and (DF)2

Abstract

We present a new full-dimensional ab initio potential energy surface (PES) of a hydrogen fluoride dimer [(HF)2] using the supermolecular approach. The calculations were performed at the coupled-cluster single double triple level, with an augmented correlation-consistent polarized valence quadruple-zeta basis set plus bond functions. The basis set superposition error was corrected by a full counterpoise procedure. With the exchange symmetry of the two HF molecules, the permutation invariant polynomial neural network approach was used to fit the hypersurface with a root-mean-square-error of 0.465 cm−1 for about 110 000 points. The ab initio noise of intermolecular potential in the long range was smoothed by the long-range coefficients method. The equilibrium configuration of the complex was found to be a Cs structure located at two equivalent minima with the well depth of 1573.495 cm−1. The eigenstates were calculated by employing a symmetry-adapted Lanczos propagation algorithm in the mixed radical discrete variable representation/angular finite basis representation. The tunneling splitting for the ground state of (HF)2 is 0.665 cm−1, agreeing well with experimental value of 0.65869 cm−1. Vibrational fundamentals are also very close to the observed values. The results of vibrational states calculations demonstrate the high accuracy of our new PES.

Breakdown of energy transfer gap laws revealed by full-dimensional quantum scattering between HF molecules

“…Our full-dimensional quantum-scattering calculations represent the first such study involving two “heavy” (non-H 2 ) molecules, and were made possible by a recently proposed scheme to reduce the size of the scattering calculations 39 . Both state-to-state cross-sections and rate coefficients are obtained, and the vibrational state-resolved rate coefficients are in excellent agreement with available experimental results, thanks to a highly accurate global PES obtained recently from high-level ab initio calculations 40 . Surprisingly, our results indicate that the energy transfer between these molecules satisfies neither the energy gap law nor angular momentum gap law.…”

“…Since TIQM scales as N 3 , where N is the dimension of the Hamiltonian matrix, the saving amounts to about 10 3 for J = 150. Our recently developed 6D PES 40 is used, which is much more accurate for scattering studies than previous PESs because it is based on high-level ab initio data, free of empirical adjustments, and accurate in both strongly interacting and in asymptote regions.…”

Soft experimental constraints for soft interactions: a spectroscopic benchmark data set for weak and strong hydrogen bonds

“…A more recent test of the back-correction reliability is possible for HFHF. 57,112 For this system, a combination of harmonic CCSD(T) basis set limit estimate and vibrational perturbation theory has yielded a surprisingly accurate match for the two HF stretching downshifts, within a few cm À1 . While there may still be some error compensation at play, it will not be very large.…”

Variational analysis of HF dimer tunneling rotational spectra using an ab initio potential energy surface

“…Variational calculations of excited rovibrational tunneling energy levels of the HF dimer are performed using the ab initio PES calculated by Huang et al [6].…”

“…PESs is presented, for example, by Klopper, Quack and Suhm [4,5]. The PES used here is due to Huang et al [6] and is based on about 100 000 points calculated using a very high level of theory. The accuracy of this PES is demonstrated below in Section 2.…”