Rough energy-landscapes of hydrated anions
The first half of this work focuses on addressing the comparative behavior of aqueous anions, F−, Cl−, Br−, I− and HO− on the basis of quasi-chemical theory (QCT). Firstly, I study structures and free energies of hydration clusters for those anions utilizing electronic structure calculations on cluster geometries sampled from an AIMD (ab initio molecular dynamics) simulation stream. This data base serves to formulate a statistical thermodynamic rough-landscape procedure that treats un- favorable ligand crowding and compares accurately with detailed thermodynamic in- formation. Secondly, I analyze the hydration structures and free energies of each ion in bulk aqueous solution with AIMD simulations and QCT. This analysis shows that QCT-defined poly-dispersity is consequential for n ≤ 3. Utilizing the results from these simulations and QCT leads to free energies and direct comparison with exper- iments. This work will help address Hofmeister ranking of ions in aqueous solutions and physical views involved in designing liquid-discharge-free desalination procedures. In the second half of this thesis, I investigate the shapes of droplets captured between two chemically distinct plates and the consequent capillary forces. This work serves as a preliminary step toward characterizing the influence of second-phase bridg- ing between biomolecular surfaces on their solution contacts, i.e., capillary attraction or repulsion.