Theory of the structure, dynamics and functionality of organic functional units on surfaces

In this project, compational chemistry methods shall be used to study the geometrical and electronic structure and the dynamics and functionality of organic functional units on surfaces. Due to the complexity of the systems, a hierarchy of different theoretical approaches shall be used. Smaller systems and the interaction between single functional units shall be addressed by first-principles electronic structure methods. This allows the analysis of their electronic, optical, chemical and catalytic properties. Larger systems and the dynamics and kinetics of the structure formation will be treated with force-field methods. These force-fields shall also be used for a pre-optimization of the structures that shall be described by first-principles methods.

In detail, first the properties of metal-molecule-metal contacts shall be theoretically addressed in close collaboration with experiments also performed within SFB. These structures are prepared by metal deposition on thin layers of small aromatic thiols such as 4-mercaptopyridine which can still be handled in DFT programmes. As a first step, the structure and stability of pure self-assembled monolayers on Au(111) shall be studied before the properties of the metal-molecule-metal contacts will be determined. We will in particular focus on the electronic properties of the contacts because of possible applications of the contacts as molecular electronics devices.

In addition, semiconducting organic layers shall be addressed which are formed from linear and cyclic arrangements of pyridines or thiophenes. We are particularly interested in the modification of the electronic and optical properties of these layers achieved through oxidation or doping. Furthermore, the process of the structure formation shall be studied with molecular dynamics and kinetic Monte Carlo simulations based on interaction parameters that are derived from force-field calculations.