Casimir Polder size consistency: a constraint violated by some dispersion theories*

A key goal in quantum chemistry methods, whether ab initio or otherwise, is to achieve size consistency. In this work we formulate the related idea of "Casimir-Polder size consistency" that manifests in long-range dispersion
energetics. We show that local approximations in time-dependent density functional theory dispersion energy calculations violate the consistency condition because of incorrect treatment of highly non-local xc kernel physics, by up to 10% in our tests on closed-shell atoms.

J. Chem. Phys., submitted October 2017