Recent Improvements to the NWChem COSMO Module

This work presents
recent developments in the COSMO solvation model
implementation in NWChem. A new cavity construction approach, based
on the solvent-excluding surface (SES) and utilizing the well-established
GEPOL algorithm, has been introduced. Additionally, a straightforward
procedure to merge surface segments that are too closeoften
a source of numerical artifactshas been implemented. The available
methods for correcting outlying surface charges have also been reviewed
and improved. To validate the new implementation, we computed dielectric
solvation energies for a chemically diverse set of approximately 100
molecules, including neutral species, small ions, and common ionic
liquid components. Results were compared to those from GAMESS using
the double-cavity method as a reference. Although the double-cavity
approach can be regarded as more accurate, the simpler correction
schemes available in NWChembased on scaling factors or Lagrange
multiplierscan achieve excellent agreement if the potential
is also properly corrected, with mean unsigned deviations of around
0.15 kcal/mol. Predictions of typical vapor–liquid and liquid–liquid
equilibria using a COSMO-SAC variant based on NWChem also showed very
promising results.