\begin{eqnarray}

E &=& 144 \phi^2 \epsilon \left[ \frac{\sigma^{6}}{7560} 

  \left(\frac{D-6R}{D^{7}} + \frac{D+8R}{(D+2R)^{7}} \right) - 

  \left(\frac{6R-D}{D^{7}} + \frac{D+8R}{(D+2R)^{7}} \right) - 

  \frac{}{} \right. \nonumber \\

  &&\qquad \left. \frac{1}{6} \left(\frac{2R(D+R) + D(D+2R)

    \left[ \ln D - \ln (D+2R) \right]}{D(D+2R)} \right) \right]