The rich and complex potential energy surface of the ethanol dimer

Abstract

The potential energy surface of the ethanol dimer is systematically explored via density functional theory and high level ab initio computations. A picture with a multitude of local minima very close in energy emerges. Three groups of interactions are at play stabilizing the dimers. On one hand, electrostatic attraction leads to a number of structures where dimers interact via hydrogen bonds. Our computations also reveal a large number of structures where the dominant stabilization arises from C–H···O hydrogen bonds and a smaller set of structures stabilized by purely dispersive interactions between the alkyl chains. Calculated shifts of the stretching O–H frequencies are in very good agreement with experimental values. Energy decomposition analysis shows that the electrostatic term dominates the stabilization of the O–H···O hydrogen bond clusters, while for the other dimers, polarization, charge transfer, and dispersion become the major stabilizing effects.