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\[
E = \lambda^n 4 \epsilon
\left\{
  \frac{1}{ \left[ \alpha_{\mathrm{LJ}} (1-\lambda)^2 +
    \left( \displaystyle\frac{r}{\sigma} \right)^6 \right]^2 } -
  \frac{1}{ \alpha_{\mathrm{LJ}} (1-\lambda)^2 +
    \left( \displaystyle\frac{r}{\sigma} \right)^6 }
\right\} \qquad r < r_c
 \]

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