Intermolecular van der Waals Interactions In ''Tight Spaces''

There are strong and substantial experimental indications that intermolecular van der Waals (vdW) interactions become reduced or even repulsive under confinement at surfaces [Phys. Rev. B 81, 035423 (2010)], inside nanotubes [Nature 537, 171 (2016)], and between 2D layers [Phys. Rev. B 94, 220102 (2016)]. These observations remain unexplained by standard treatments of vdW interactions based on a dipolar approximation, which predict universal long-range attraction between vdW dimers. Using the Drude response model of valence electrons, recently we have shown that the long-range electron correlation between spatially confined vdW dimers becomes repulsive when accounting for the full-Coulomb interaction between charge fluctuations [Phys. Rev. Lett. 118, 210402 (2017)]. Here we further develop an atomistic theory for full Coulomb coupled oscillators based on a microscopic many-body dispersion (MBD) Hamiltonian [Phys. Rev. Lett. 108, 236402 (2012)]. We apply this model to study the interplay between London attraction and vdW repulsion for intermolecular interactions in nanotubes, at surfaces, and between 2D materials. We find that repulsive vdW correlations in ``tight spaces'' can provide an additional degree of freedom for molecular self assembly.