Coupled cluster and density functional investigation of the neutral sodium-benzene and potassium-benzene complexes

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

The isotropic and anisotropic coefficients C_n ^l,m of the long-range spherical expansion ∼1/Rⁿ (R-the intermolecular distance) of the dispersion and induction 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_n,disp ^l,m and induction C_n,ind ^l,m coefficients (C_n ^l,m=C_n,disp ^l,m+C_n,ind ^l,m) 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 ≈ 6 Å. 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.

Interactions of benzene, naphthalene, and azulene with alkali-metal and alkaline-earth-metal atoms for ultracold studies

We consider collisional properties of polyatomic aromatic hydrocarbon molecules immersed into ultracold atomic gases and investigate intermolecular interactions of exemplary benzene, naphthalene, and azulene with alkali-metal (Li, Na, K, Rb, and Cs) and alkaline-earth-metal (Mg, Ca, Sr, and Ba) atoms. We apply the state-of-the-art ab initio techniques to compute the potential energy surfaces (PESs). We use the coupled cluster method restricted to single, double, and noniterative triple excitations to reproduce the correlation energy and the small-core energy-consistent pseudopotentials to model the scalar relativistic effects in heavier metal atoms. We also report the leading long-range isotropic and anisotropic dispersion and induction interaction coefficients. The PESs are characterized in detail, and the nature of intermolecular interactions is analyzed and benchmarked using symmetry-adapted perturbation theory. The full three-dimensional PESs are provided for the selected systems within the atom-bond pairwise additive representation and can be employed in scattering calculations. The present study of the electronic structure is the first step toward the evaluation of prospects for sympathetic cooling of polyatomic aromatic molecules with ultracold atoms. We suggest azulene, an isomer of naphthalene which possesses a significant permanent electric dipole moment and optical transitions in the visible range, as a promising candidate for electric field manipulation and buffer-gas or sympathetic cooling.

Theoretical characterization of hexagonal 2D Be3N2 monolayers

With the help of DFT calculations, a possible synthesis method for monolayer Be₃N₂ is proposed. Furthermore, its excellent thermal, dynamical, and mechanical stability makes it a material of comparable caliber to that of graphene.

Unusual Enhancement of the Adsorption Energies of Sodium and Potassium in Sulfur-Nitrogen and Silicon-Boron Codoped Graphene

Herein, we have employed first-principles calculations to investigate the interaction between XY dual-doped graphene (DDG) (X = AL, Si, P, S; Y = B, N, O) and sodium/potassium. The introduction of two dopants alters the adsorption energy (AE) of sodium and potassium with respect to perfect graphene by an average of 0.88 and 0.66 eV, respectively. The systems that display the strongest interactions with the two alkalies assayed are SN and SiB DDG. Although the adsorption energy of sodium on graphene is weaker in comparison to that of potassium, the introduction of these dopants significantly reduces this difference. In effect, in some cases, the AE-K and AE-NA differ by less than 0.05 eV. The protrusion of the 3p dopants out of the graphene plane creates a hole where sodium and potassium can easily be intercalated between two layers of dual-doped graphene. The interlayer distances are reduced by less than 0.4 Å after K intercalation, making the process very favorable. Finally, most importantly, this eminent rise in adsorption energies guarantees exceptional storage capacities at the cost of low doping concentration.