Anisotropic van der Waals dispersion forces in polymers: Structural symmetry breaking leads to enhanced conformational search

Abstract

The modeling of conformations and dynamics of (bio)polymers is of primary importance for understanding the physicochemical properties of soft matter. Although short-range interactions such as covalent and hydrogen bonding control the local arrangement of polymers, noncovalent interactions play a dominant role in determining the global conformations. Here, we focus on how the inclusion of many-body effects in van der Waals (vdW) dispersion influences the molecular dynamics of model polymers and a polyalanine chain studied with semiempirical quantum mechanics. We show that delocalized force contributions are key to exploring the conformational landscape, as they induce an anisotropic polarization response which efficiently guides the conformation towards globally optimized structures. This is in contrast with the commonly used pairwise interatomic Lennard-Jones-like potentials, which result in structures that optimize local regularity rather than global symmetries. The many-body vdW formalism results in a significant reduction in the roughness of the energy landscape and drives the conformational search towards geometries that are consistent with global spatial symmetries.