Continuous shouldered well model

The continuous shouldered well model (CSW) is given by (^[1] Eq. 1):

\Phi _{12}(r)={\frac {U_{R}}{1+\exp[\Delta (r-R_{R})/a]}}-U_{A}\exp \left[-{\frac {(r-R_{A})^{2}}{2\delta _{A}^{2}}}\right]+\left({\frac {a}{r}}\right)^{24}

where $\Phi _{12}$ is the intermolecular pair potential, $U_{R}$ is the energy of the repulsive shoulder, Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle U_{A}} is the energy of the attractive well, $a$ is the diameter of the particles, and $r:=|\mathbf {r} _{1}-\mathbf {r} _{2}|$ .