A potential surface for the interaction between water and coronene as a model for a hydrophobic surface

Abstract

The potential energy surface for the interaction of a coronene molecule, as a model for a graphitic sheet, with a water molecule over its central ring has been calculated at the DFT and MP2 levels. The lowest energy orientation has both hydrogen atoms of the water pointing down symmetrically towards the coronene surface; this is also the preferred geometry for circumcoronene, C₅₄H₁₈. This is different from the water–benzene system, where the minimum is asymmetric, with one hydrogen pointing towards one of the carbon atoms in the ring. The coronene–water interaction energies were parameterized as a function of the Euler angles that describe the orientation of the water molecule and the distance between the oxygen atom and the coronene plane. The symmetry and distance dependence of the angular components were used to determine the physical origin of each term.

Keywords:

• hydrophobic interaction
• coronene
• circumcoronene
• dipole–quadrupole
• dipole-induced dipole

Acknowledgements

This work was supported by the National Science Foundation (grant No. CHE-0515922) and the Mildred B. Cooper Chair at the University of Arkansas. Funds for the acquisition of the Red Diamond supercomputer were provided, in part, by the National Science Foundation under grant No. MRI-0421099.