Weak Noncovalent Interactions in Nonequilibrium Structures: How Good Are the Dispersion Corrections?

Noncovalent interactions exhibit features that are not
always
well-described by density functional theory, even when specific corrections
are applied. This is illustrated by the series of acene and polyene
dimers in eclipsed arrangements, which, being far from their energy
minima, highlight the challenges associated with nonequilibrium structures.
For these systems, the most common dispersion corrections, including
some of the D-family, XDM, VV10, and MBD, were tested. Our results
show that corrections relying on information from the electron density,
such as VV10 and MBD, are capable of handling these challenging cases,
while other approaches show errors that increase with system size.
This analysis suggests that nonequilibrium geometries are insufficiently
represented in the parametrization of dispersion corrections, a shortcoming
that could significantly affect the modeling of systems under “real
life” conditions.