Scaling properties of liquid dynamics predicted from a single configuration: Small rigid molecules

TL;DR

This paper extends a force-based isomorph tracing method, originally for atomic systems, to small rigid molecules, demonstrating that a single configuration suffices to predict liquid dynamics across different molecular models.

Contribution

The study generalizes a force-based isomorph prediction method to molecular systems, showing it effectively predicts liquid dynamics with minimal configurations.

Findings

The center-of-mass force invariance method performs best among tested approaches.

A single equilibrium configuration can accurately trace out isomorphs in molecular models.

The method works well for different simple molecular models.

Abstract

Isomorphs are curves in the thermodynamic phase diagram along which structure and dynamics are invariant to a good approximation. There are two main ways to trace out isomorphs, the configurational-adiabat method and the direct-isomorph-check method. Recently a new method based on the scaling properties of forces was introduced and shown to work very well for atomic systems [T. B. Schroder, Phys. Rev. Lett. 129, 245501 (2022)]. A unique feature of this method is that it only requires a single equilibrium configuration for tracing out an isomorph. We here test generalizations of this method to molecular systems and compare to simulations of three simple molecular models: the asymmetric dumbbell model of two Lennard-Jones spheres, the symmetric inverse-power-law dumbbell model, and the Lewis-Wahnstr\"om o-terphenyl model. We introduce and test two force-based and one torque-based methods, all of which require just a single configuration for tracing out an isomorph. Overall, the method based on requiring invariant center-of-mass reduced forces works best.