Power of the Many‐Body Force: Magnitudes and Angles of Atomic Van der Waals Dispersion Forces in Extended Molecular Systems

A distinctive feature of soft materials such as polymers, liquids, biomolecules, and nanostructures is that their macroscopic properties are highly dependent on structural dynamics, even at equilibrium. This is a consequence of fewer covalent bonds when compared to hard solids, which grants soft materials higher structural flexibility, mostly controlled by noncovalent forces such as van der Waals dispersion (vdW) interactions. Although vdW energies have been investigated thoroughly in a wide range of systems, much less is known about the magnitudes and orientations of atomic vdW forces beyond the highly approximate pairwise (PW) Lennard–Jones‐like potentials. The present study compares PW and quantum‐mechanical many‐body vdW forces in large molecular systems with a varying degree of structural order. Many‐body effects can enhance atomic vdW forces by up to 300% and introduce significant angular deviations of up to 60 degrees on average. The changes in the power‐law decay rate alone account for a significant portion of the many‐body contributions, indicating that an effective PW potential tailored to reproduce the decay rate of many‐body dispersion will already be more accurate than standard models. These results highlight how collective phenomena in soft matter can be rationalized through a more accurate quantum‐informed perspective on vdW forces.