Thermal and Electronic Fluctuations of Flexible Adsorbed Molecules: Azobenzene on Ag(111).
We investigate the thermal and electronic collective fluctuations that contribute to the finite-temperature adsorption properties of flexible adsorbates on surfaces on the example of the molecular switch azobenzene C_{12}H_{10}N_{2} 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 10^{24}  s^{-1} that largely exceeds previously reported estimates. We relate this effect to sizable fluctuations across structural and electronic observables. A comparison of our calculations to temperature-programed 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.
Department Chemie, Technische Universität München, D-85748 Garching, Germany.|Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA.
Reinhard J
RJ
Maurer
Fritz-Haber Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.|Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China.
Wei
W
Liu
Fritz-Haber Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.|Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Luxembourg.
Igor
I
Poltavsky
Department Chemie, Technische Universität München, D-85748 Garching, Germany.
Thomas
T
Stecher
Department Chemie, Technische Universität München, D-85748 Garching, Germany.
Harald
H
Oberhofer
Department Chemie, Technische Universität München, D-85748 Garching, Germany.
Karsten
K
Reuter
Fritz-Haber Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.|Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Luxembourg.
Alexandre
A
Tkatchenko