(712c) Ion Hydration at Short and Long Length Scales Conference: AIChE Annual MeetingYear: 2015Proceeding: 2015 AIChE Annual MeetingGroup: Engineering Sciences and FundamentalsSession: Thermodynamics at the Nanoscale II Time: Thursday, November 12, 2015 - 1:15pm-1:30pm Authors: Vlcek, L., Oak Ridge National Laboratory Chialvo, A. A., Oak Ridge National Laboratory Experimental studies of clusters comprised of an ion and solvent (water) molecules are a rich source of information about the details of ion solvation thermodynamics, which is otherwise experimentally inaccessible in bulk solution conditions. However, experiments based on mass spectrometry measurement of cluster-size distribution are limited only to clusters with water molecules in the first few hydrtion shells, leaving the region of larger clusters unexplored. We use combined classical and quantum mechanical Monte Carlo simulations to investigate the factors influencing ion hydration in small aqueous clusters and the thermodynamic changes accompanying the transition to bulk hydration.1,2 The results indicate that large systematic changes occurr at the vapor-liquid interface of the aqueous cluster-ions, which impact the overall thermodynamics and the relative favorability of cation and anion hydration. We discuss implications of these insights for the determination of single-ion hydration properties and for the methodology of classical and quantum simulations of aqueous electrolytes.3  Vlcek L., Chialvo A.A., Simonson J.M.: Correspondence between cluster-ion and bulk thermodynamic properties: on the validity of the cluster-pair-based approximation, J. Phys. Chem. A, 117(14), 11328-11338 (2013).  Vlcek L., Uhlik F., Moucka F., Nezbeda I., Chialvo A.A.: Thermodynamics of Small Alkali Metal Halide Cluster Ions: Comparison of Classical Molecular Simulations with Experiment and Quantum Chemistry. J. Phys. Chem. A 119(3), 488-500 (2015)  Vlcek L., Chialvo A.A.: Single-Ion Hydration Thermodynamics from Clusters to Bulk Solutions: Recent Insights from Molecular Modeling. Fluid Phase Equil. in review (2015).