Emergent Rate Laws for Collective Lying-Standing Transitions

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Lying-standing transitions in molecular monolayers at organic-inorganic interfaces significantly impact interface properties like dipoles and energy levels.
• Predicting the collective kinetics of these transitions is challenging due to complex interplay of molecular behaviors.

Purpose of the Study:

• To establish a quantitative relationship between adsorbate properties and transition kinetics for lying-standing transformations.
• To develop a predictive model for collective transition rates based on microscopic processes.

Main Methods:

• Utilized first-principles-based kinetic Monte Carlo simulations.
• Employed a mean-field coarse-graining strategy for computational efficiency.
• Investigated the prototypical system of tetracyanoethylene on Cu(111).

Main Results:

• Collective transition rates emerge from coupled processes (reorientation, adsorption, diffusion), not single steps.
• A geometric factor quantitatively explains deviations between single-molecule and collective rates.
• Molecular geometry, specifically footprint ratio, acts as a control parameter, accelerating transitions.

Conclusions:

• Derived an analytical expression linking microscopic rates to geometric parameters for collective reorientation.
• The model accurately reproduces simulation results across different kinetic regimes.
• Provides transferable design principles for controlling transition timescales at organic-inorganic interfaces.