We
propose a computationally lean, two-stage approach that reliably
predicts self-assembly behavior of complex charged molecules on metallic
surfaces under electrochemical conditions. Stage one uses ab initio
simulations to provide reference data for the energies (evaluated
for archetypical configurations) to fit the parameters of a conceptually
much simpler and computationally less expensive force field of the
molecules: classical, spherical particles, representing the respective
atomic entities; a flat and perfectly conducting wall represents the
metallic surface. Stage two feeds the energies that emerge from this
force field into highly efficient and reliable optimization techniques
to identify via energy minimization the ordered ground-state configurations
of the molecules. We demonstrate the power of our approach by successfully
reproducing, on a semiquantitative level, the intricate supramolecular
ordering observed experimentally for PQP
+
and ClO
4
–
molecules
at an Au(111)–electrolyte interface, including the formation
of open-porous, self-host–guest, and stratified bilayer phases
as a function of the electric field at the solid–liquid interface.
We also discuss the role of the perchlorate ions in the self-assembly
process, whose positions could not be identified in the related experimental
investigations.