Long-range interactions of aromatic molecules with alkali-metal and alkaline-earth-metal atoms

TL;DR

This paper calculates long-range interaction coefficients for aromatic molecules with alkali and alkaline-earth atoms, providing detailed data crucial for modeling van der Waals forces in spectroscopic and scattering research.

Contribution

It introduces first-principles calculations of dispersion and induction coefficients up to n=12 for aromatic-atom complexes, including higher-order terms for accurate interaction modeling.

Findings

Inclusion of coefficients with n>6 improves interaction energy accuracy at R≈6 Å.

Provides comprehensive long-range potential data for aromatic-atom complexes.

Highlights importance of higher-order terms in van der Waals region modeling.

Abstract

The isotropic and anisotropic coefficients $C^{l,m}_n$ of the long-range spherical expansion $\sim 1/R^n$ ($R$ -- the intermolecular distance) of the dispersion and inductions intermolecular energies are calculated using the first principles for the complexes containing an aromatic molecule (benzene, pyridine, furan, and pyrrole) and alkali-metal (Li, Na, K, Rb, and Cs) or alkaline-earth-metal (Be, Mg, Ca, Sr, and Ba) atoms in their electronic ground states. The values of the first and second-order properties of the aromatic molecules are calculated using the response theory with the asymptotically corrected LPBE0 functional. The second-order properties of the closed-shell alkaline-earth-metal atoms are obtained using the expectation-value coupled cluster theory and of the open-shell alkali-metal atoms using analytical wavefunctions. These properties are used for the calculation of the dispersion $C^{l,m}_{n,\text{disp}}$ and induction $C^{l,m}_{n,\text{ind}}$ coefficients ($C^{l,m}_n=C^{l,m}_{n,\text{disp}}+C^{l,m}_{n,\text{ind}}$) with $n$ up to 12 using the available implemented analytical formulas. It is shown that the inclusion of the coefficients with $n>6$ is important for reproducing the interaction energy in the van der Waals region at $R\approx 6$ angstrom. The reported long-range potentials should be useful for constructing the analytical potentials, valid for the whole intermolecular interaction range, which are needed for spectroscopic and scattering studies.