In previous versions of QUBEKit, we have computed the electron density using a minimal parameter solvent model, with the solute cavity defined by an isosurface of the electron density. We argued that a solvent dielectric = 4 is appropriate, as it leads to charges that are polarised midway between vacuum and a dielectric medium of = 78 (i.e. water). Gaussian09 provides the IPCM implicit solvent model, which also builds the solute cavity from an isosurface of the electron density, and so we use this model as our default here.