In our pursuit of an accurate description of interlayer interactions in twisted bilayer graphynes, the explicit incorporation of anisotropy into the potential formulation holds the key.

Alongside the evolution of density functional theory into a new era led by the dispersion-corrected hybrid density functional theory approaches, formulation of a new generation of intermolecular potentials has also taken the center stage. An ideal potential formulation should desirably possess simplicity of functional forms, physically meaningful parameters, separability of various terms into atomic-level contributions, computational tractability, ability to capture non-additivity of interactions, transferability across different chemical species, and crucially, chemical fidelity in terms of reproducing the benchmark data. The Lennard-Jones potential, one of the popular intermolecular pair potentials for performing large-scale simulations fails to capture the intricate features of molecular interactions. Woven around the central theme of anisotropy in the nature of intermolecular interactions, herein, we describe various landmark contributions in the quest for chemical fidelity of empirical potential formulations that include (i) incorporation of the anisotropic nature of exchange-repulsion and dispersion contributions, (ii) multipolar description of the dispersion terms, (iii) damping functions to provide an accurate description of the asymptotes, and (iv) transferability of intermolecular interaction terms. We illustrate the nuances of intermolecular force field development in the context of modeling the non-covalent interactions governing the (i) binding of atoms and molecules with carbon nanostructures, (ii) molecular aggregates of polycyclic aromatic hydrocarbons, and (iii) interlayer interactions in layered nanostructures. We exemplify the hierarchy of empirical potentials by depicting them on the various rungs of the Jacob's ladder equivalent of density functional theory for the intermolecular force fields. Finally, we discuss some possible futuristic directions in intermolecular force field development.

Graphynes are a class of all-carbon two-dimensional membranes that have been intensely researched for various membrane-based technologies on account of their unique pore architectures. Herein, we report an investigation of the mechanism and energetics of adsorption of noble gases (He, Ne and Ar) on graphdiyne (GDY), the most popular form of graphynes. Two global optimization techniques, namely particle swarm optimization (PSO) and differential evolution are employed to predict the putative global minima configurations of rare gas clusters in the size range 1-30 when adsorbed on GDY. We use the 12-6 Lennard-Jones potential to represent the pairwise non-covalent interactions between various interacting atoms. Initially, the gas atoms adsorb as monolayers on GDY at the centers of the triangular pores until all the triangular pores are filled. This is followed by a second layer formation on top of the hexagonal pore centers or on top of the CÀ C bonds. The findings from the empirical approach are further validated by performing density functional theory calculations on the predicted adsorbed cluster configurations. We have also looked into the adsorption of noble gas clusters on bilayer GDY systems and have found that the intercalation of gas atoms within the bilayers is feasible. Our study suggests that the stochastic nature of the swarm intelligence technique, PSO can assist in an effective search of the potential energy surfaces for the global minima, eventually enabling large-scale simulations.