Electrochemical Surface
Potential Due to Classical
Point Charge Models Drives Anion Adsorption to the Air–Water
Interface
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Abstract
We demonstrate that the driving forces for ion adsorption
to the
air–water interface for point charge models result from both
cavitation and a term that is of the form of a negative electrochemical
surface potential. We carefully characterize the role of the free
energy due to the <i>electrochemical</i> surface potential
computed from simple empirical models and its role in ionic adsorption
within the context of dielectric continuum theory. Our research suggests
that the electrochemical surface potential due to point charge models
provides anions with a significant driving force for adsoprtion to
the air–water interface. This is contrary to the results of
ab initio simulations that indicate that the <i>average electrostatic</i> surface potential should favor the desorption of anions at the air–water
interface. The results have profound implications for the studies
of ionic distributions in the vicinity of hydrophobic surfaces and
proteins