Effects of many-body dispersion interactions on phase transitions of coarse-grained polymers

Non-covalent interactions are crucial to the structure formation of soft matter. An important role is played by the van der Waals dispersion interaction, which is often modelled by efficient, but incomplete pairwise (PW) approximations. Substantially more accurate interaction energies are provided by the more recent many-body dispersion model (MBD) [1], but its relevance for (thermo)dynamic properties remains largely unexplored. In particular, since MBD predicts an increased effective interaction range which depends on the global configuration of the system, we anticipate enhanced cooperativity in conformational changes of polymers.

Here, we adapt microcanonical inflection point analysis [2] to characterize these effects in phase transitions of small, flexible model polymers. We ensure comprehensive sampling of their configurational space by running extensive canonical replica-exchange molecular dynamics. By reweighting, we compute relevant microcanonical observables and explore how the description of the dispersion interaction (PW or MBD) manifests in the properties of the polymer's clustering transition.

[1] Tkatchenko et al, PRL 108, 23, 236402 (2012)

[2] Schnabel, Seaton, Landau and Bachmann, PRE 84, 1, 011127 (2011)