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Abstract:
We investigate the thermal and electronic collective
fluctuations that contribute to the finitetemperature
adsorption properties of
flexible adsorbates on surfaces on the example of the molecular
switch azobenzene C12H10N2 on the Ag(111) surface. Using first-principles molecular dynamics simulations
we obtain the free energy of adsorption that accurately accounts for entropic contributions,
whereas the inclusion of many-body dispersion interactions accounts for the electronic correlations
that govern the adsorbate binding. We find the adsorbate properties to be strongly entropy-driven,
as can be judged by a kinetic molecular desorption prefactor of 1024 s-1 that largely exceeds previously
reported estimates. We relate this effect to sizable
fluctuations across structural and electronic
observables. Comparison of our calculations to temperature-programmed desorption measurements
demonstrates that finite-temperature effects play a dominant role for
flexible molecules in contact
with polarizable surfaces, and that recently developed first-principles methods offer an optimal tool
to reveal novel collective behavior in such complex systems.
