Guest Talk by TU Dresden Senior Fellow Dr. Nicolas Lorente (CSIC-EHU)
Published on in NEWS
Dr. Nicolas Lorente from "Centro de Física de Materiales Centro Mixto CSIC-UPV/EHU" and "Donostia International Physics Center (DIPC)" joins cfaed in September 2019 as a TU Dresden Senior Fellow. He is hosted by cfaed Research Group Leader Dr. Francesca Moresco. His research interest focuses on quantum phenomena on surfaces.
On Wednesday, 18 September 2019, he will give a guest lecture about "Weakly-bound supramolecular structures: calculations for understanding experiments with the scanning tunneling microscope". The lecture is open to the public.
Time: 13:00 - 14:00; Location: TU Dresden, Barkhausenbau, room BAR I88, Georg-Schumann-Str. 11, 01187 Dresden
4-Acetylbiphenyl is a small aromatic molecule that binds via dispersive forces (van der Waals interaction) with a gold surface. Experiments performed in the group of Dr. Moresco in TU Dresden show that under certain conditions of deposition these molecules formed a 4-molecule superstructure nicknamed the “windmill” because of its cross-shaped structure. Hydrogen bonding is known to be efficient in creating molecular superstructures, and the presence of oxygen in the acetyl group makes it natural to assign the formation of the supramolecular structure to H-bonding. Closer inspection of the scanning tunneling microscope images (STM) reveals that the unique seemingly H-bond should take place between a methyl group and the O atoms. This is one of the weakest H bonds if it binds at all. We undertook density functional theory calculations completed by empirical van-der-Waals corrections to study the supramolecular structure. From the simulation of STM images, total energy calculations and Gibbs free-energy estimates, we reach the startling conclusion that windmills take place only if gold adatoms join the four acetylbiphenyl molecules together.