Weeks-Chandler-Andersen perturbation theory

The Weeks-Chandler-Anderson perturbation theory is based on the following decomposition of the intermolecular pair potential (in particular, the Lennard-Jones potential):

The reference system pair potential is given by (Eq, 4):

${\mathrm{\Phi }}_{\mathrm{r}\mathrm{e}\mathrm{p}\mathrm{u}\mathrm{l}\mathrm{s}\mathrm{i}\mathrm{v}\mathrm{e}}(r)=\{\begin{array}{cc}{\mathrm{\Phi }}_{\mathrm{L}\mathrm{J}}(r)+ϵ& r<2^{1/6}\sigma \\ 0& r\ge 2^{1/6}\sigma \end{array}$

and the perturbation potential is given by (Eq, 5 Ref. 1):

${\mathrm{\Phi }}_{\mathrm{a}\mathrm{t}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}}(r)=\{\begin{array}{cc}-ϵ& r<2^{1/6}\sigma \\ {\mathrm{\Phi }}_{\mathrm{L}\mathrm{J}}(r)& r\ge 2^{1/6}\sigma \end{array}$

Colloids

The repulsive component of the WCA decomposition has been used as a model for colloids .