  General properties of the recently observed screening of the van der Waals
(vdW) attraction between a silica substrate and silica tip by insertion of
graphene are predicted using basic theory and first-principles calculations.
Results are then focused on possible practical applications, as well as an
understanding of the nature of vdW attraction, considering recent discoveries
showing it competing against covalent and ionic bonding. The traditional view
of the vdW attraction as arising from pairwise-additive London dispersion
forces is considered using Grimme's "D3" method, comparing results to those
from Tkatchenko's more general many-body dispersion (MBD) approach, all
interpreted in terms of Dobson's general dispersion framework. Encompassing the
experimental results, MBD screening of the vdW force between two silica
bilayers is shown to scale up to medium separations as 1.25 de/d, where d is
the bilayer separation and de its equilibrium value, depicting antiscreening
approaching and inside de. Means of unifying this correlation effect with those
included in modern density functionals are urgently required.
