  By explicitly including fractionally ionic contributions to the
polarizability of a many-component system we are able to significantly improve
on previous atom-wise many-body van der Waals approaches with essentially no
extra numerical cost. For non-ionic systems our method is comparable in
accuracy to existing approaches. However, it offers substantial improvements in
ionic solids, e.g. producing better polarizabilities by over 65% in some cases.
It has particular benefits for two-dimensional transition metal
dichalcogenides, and interactions of H$_2$ with modified coronenes - ionic
systems of nanotechnological interest. It thus offers an efficient improvement
on existing approaches, valid for a wide range of systems.
