Weeks-Chandler-Andersen perturbation theory

The Weeks-Chandler-Andersen 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):

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \Phi_{\rm repulsive} (r) = \left\{ \begin{array}{ll} \Phi_{\rm LJ}(r) + \epsilon & {\rm if} \; r < 2^{1/6}\sigma \\ 0 & {\rm if} \; r \ge 2^{1/6}\sigma \end{array} \right. }

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

$\Phi _{\rm {attractive}}(r)=\left\{{\begin{array}{ll}-\epsilon &{\rm {if}}\;r<2^{1/6}\sigma \\\Phi _{\rm {LJ}}(r)&{\rm {if}}\;r\geq 2^{1/6}\sigma \end{array}}\right.$

Colloids

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