Thermodynamic uncertainty relation for Langevin dynamics by scaling time

The thermodynamic uncertainty relation (TUR) quantifies a relationship between current fluctuations and dissipation in out-of-equilibrium overdamped Langevin dynamics, making it a natural counterpart of the fluctuation-dissipation theorem in equilibrium statistical mechanics. For underdamped Langevin dynamics, the situation is known to be more complicated, with dynamical activity also playing a role in limiting the magnitude of current fluctuations. Progress on those underdamped TUR-like bounds has largely come from applications of the information-theoretic Cram\'er-Rao inequality. Here, we present an alternative perspective by employing large deviation theory. The approach offers a general, unified treatment of TUR-like bounds for both overdamped and underdamped Langevin dynamics built upon current fluctuations achieved by scaling time. The bounds we derive following this approach are similar to known results but with differences we discuss and rationalize.Comment: 6 pages, 3 figure

In Silico Design of 2D and 3D Covalent Organic Frameworks for Methane Storage Applications

Here, we present a database of 69 840 largely novel covalent organic frameworks assembled in silico from 666 distinct organic linkers and four established synthetic routes. Due to their light weights and high internal surface areas, the frameworks are promising materials for methane storage applications. To assess their methane storage performance, we used grand-canonical Monte Carlo simulations to calculate their deliverable capacities. We demonstrate that the best structure, composed of carbon–carbon bonded triazine linkers in the tbd topology, has a predicted 65-bar deliverable capacity of 216 v STP/v, better than the best methane storage materials published to date. Using our approach, we also discovered other high-performing materials with 300 structures having calculated deliverable capacities greater than 190 v STP/v and 10% of these outperforming 200 v STP/v. To encourage screening studies of these materials for other applications, all structures and their properties were made available on the Materials Cloud

Limits on the Precision of Catenane Molecular Motors: Insights from Thermodynamics and Molecular Dynamics Simulations

Thermodynamic uncertainty relations (TURs) relate precision to the dissipation rate, yet the inequalities can be far from saturation. Indeed, in catenane molecular motor simulations, we record precision far below the TUR limit. We further show that this inefficiency can be anticipated by four physical parameters: the thermodynamic driving force, fuel decomposition rate, coupling between fuel decomposition and motor motion, and rate of undriven motor motion. The physical insights might assist in designing molecular motors in the future