Quantum-mechanical van der Waals Interactions from Atoms to Asteroids

Noncovalent van der Waals (vdW) interactions arise from quantum-mechanical electronic and atomic fluctuations and they are ubiquitous in essentially all molecules and materials [RMP 88, 045003; Chem. Rev. 117, 4714; Science 351, 1171]. Intergrain vdW interactions have even been hypothesized to explain cohesion in kilometer-sized rubble pile asteroids in space [Nature 512, 174]. I will review the substantial progress in our understanding of everpresent quantum vdW forces at the atomic, nano, and mesoscopic scales achieved during the last two decades. Then I will turn to big gaps in our knowledge where intensive research is required, including (i) the unification of vdW methods with semilocal density functionals, (ii) the scaling of vdW forces with topology, dimensionality, size, and electronic properties of materials, (iii) the interplay between atomic vibrations and electronic fluctuations in the vdW forces, (iv) the delicate transition between vdW and Casimir physics in complex systems.