Structural Transitions at Dense Arrays of Protogenic Surface Groups

Structural Transitions at Dense Arrays of Protogenic Surface Groups 

Calculations were performed on a unit cell with three SGs and three water molecules. The main model system studied was of an array of SGs of the type 

In this definition, E incorporates correlation energies between SGs due to electrostatic interactions and hydrogen bonding in the interfacial layer. 

Upon increasing dec the fully dissociated upright structure destabilizes. The average hydrogen bond distance increases from doo = 2.6 A at dec 6.2 A to 

A transition from fully dissociated to partially dissociated tilted configuration occurs at dec = 8.7 A with two H2O and one H3O+ ion remaining per unit cell. At dec = 9.2 A, another transition from a partially dissociated to a completely nondis-sociated state occurs. At dec beyond this point, every acid group retains only one 

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