A simple way of understanding the nonadditivity of van der Waals dispersion forces

Using a semiclassical model for three interacting fluctuating dipoles we in troduce a simple scenario in which the nonadditivity of the van der Waals d ispersion forces arises in a very transparent way. For simplicity, we illus trate our model in the case of nonretarded dispersion forces. The argument can be straightforwardly generalized to the case of N interacting fluctuati ng dipoles. For pedagogical reasons, we also give a brief review of some ba sic points concerning van der Waals forces. (C) 1999 American Association o f Physics Teachers.