Non-conventional screening of the Coulomb interaction in low-dimensional and finite-size systems

We study the screening of the Coulomb interaction in non-polar systems by p olarizable atoms. We show that in low dimensions and small finite-size syst ems this screening deviates strongly from that conventionally assumed. In f act in one dimension the short-range interaction is strongly screened and t he long-range interaction is anti-screened thereby strongly reducing the gr adient of the Coulomb interaction and therefore the correlation effects. We argue that this effect explains the success of mean-field single-particle theories for large molecules.