Speaker
Description
Modelling of dielectric interfaces remains a central challenge in computational chemistry. Compared to solid-liquid or solid-gas interfaces, liquid-liquid and liquid-gas interfaces have so far received relatively little attention. We present a new method to incorporate solvation effects into density-functional theory calculations of organic adsorbates at such interfaces. Simulating a large number of solvent molecules explicitly at this first-principles level is not computationally tractable. We therefore resort to an implicit solvation approach, treating the solvent as a structureless dielectric medium.
Specifically, we advance the multipole expansion method, in which we model the interface as the boundary of two semi-infinite media with different permittivity. Our recent introduction of a piecewise multipole expansion [1] into this method allows us to accurately capture the dielectric response for larger adsorbates with an overall non-convex hull, with electrostatic interaction energies converged up to few meV. Free energy contributions beyond classical electrostatics are approximated by effective interface tensions.
Gauging the limiting behavior for moving the solute from one bulk medium into the other can straightforwardly be achieved by referencing against experimental transfer free energies. The behavior at the interface itself can be validated against force-field level molecular dynamics (MD) simulations with explicit solvent molecules, which are themselves in good agreement with experimental photoelectron angular distribution data [2]. These MD calculations yield thermal distributions of the solute atomic positions relative to the instantaneous interface. In our above described continuum model, corresponding distributions can be obtained by Monte Carlo sampling, this way enabling a direct comparison between the explicit and the implicit model. The role of the solvent structure in the adsorption can thus be assessed, revealing the capabilities, limitations and possible refinements of our continuum model.
[1] J. Filser, K. Reuter, and H. Oberhofer, J. Chem. Theory Comput. 18, 461 (2022).
[2] R. Dupuy, J. Filser, C. Richter, R. Seidel, F. Trinter, T. Buttersack, C. Nicolas, J. Bozek, U. Hergenhahn, H. Oberhofer, B. Winter, K. Reuter, and H. Bluhm, Phys. Chem. Chem. Phys. 24, 4796 (2022).
| Abstract Number (department-wise) | TH 15 |
|---|---|
| Department | TH (Reuter) |
