Thermally activated snap-through transitions controlled by tunable free energy landscape

Abstract

The effects of thermal fluctuations on the morphology of two-dimensional elastic materials are hard to harness. We propose that such effects can be controlled and exploited in thermally activated snap-through transitions of geometrically constrained graphene nanoribbons (GNRs) with a tunable transition rate constant. The energetics and kinetics of these transitions can be fully characterized by combining enhanced sampling methods and generalized transition state theory. Using well-tempered metadynamics, we determine the complex free energy landscape and a pair of degenerate transition pathways of the GNR system. The resultant Landau free energy allows the application of generalized transition state theory (TST). Notably, generalized TST accurately captures how the transition rate constant responds to temperature and the tunable free energy landscape of our system, as substantiated by unbiased and accelerated molecular dynamics simulations for the rare event dynamics across different timescales. This work offers a theoretical framework for elastic metastability, introduces rare event methods into thermalized nanomechanical systems, and provides strategies for controlling thermally activated transitions in metastable elastic nanostructures.