Abstract
Ensemble averaging of molecular states is fundamental for the experimental determination of thermodynamic quantities. A special case occurs for single-molecule investigations under equilibrium conditions, for which free energy, entropy and enthalpy at finite temperatures are challenging to determine with ensemble averaging alone. Here we report a method to directly record time-averaged equilibrium probability distributions by confining an individual molecule to a nanoscopic pore of a two-dimensional metal-organic nanomesh, using temperature-controlled scanning tunnelling microscopy. We associate these distributions with partition function projections to assess real-space-projected thermodynamic quantities, aided by computational modelling. The presented molecular dynamics-based analysis is able to reproduce experimentally observed projected microstates with high accuracy. By an in silico customized energy landscape, we demonstrate that distinct probability distributions can be encrypted at different temperatures. Such modulation provides means to encode and decode information into position-temperature space.
Highlights
Ensemble averaging of molecular states is fundamental for the experimental determination of thermodynamic quantities
The dynamic behaviour of organic molecules at homogenous surfaces has been extensively studied and deep insight has been gained in their mobility characteristics
Through adequate assembly protocols we prepared metal-organic nanomeshes (MONs) with mainly single molecules captured in the hexagonal pores
Summary
Ensemble averaging of molecular states is fundamental for the experimental determination of thermodynamic quantities. We report a method to directly record time-averaged equilibrium probability distributions by confining an individual molecule to a nanoscopic pore of a two-dimensional metal-organic nanomesh, using temperaturecontrolled scanning tunnelling microscopy. We associate these distributions with partition function projections to assess real-space-projected thermodynamic quantities, aided by computational modelling. Statistical thermodynamics is one of the pillars of the atomistic theory of matter[1,2,3] In this context, the partition function plays a central role, bridging the distribution of states in a given system with macroscopic quantities, such as the free energy or specific heats. It is clear that the exploration of the spatial degrees of freedom underlying the configurational partition function can be expressed geometrically for a given system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
