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\begin{eqnarray*}
  E & = & E_i + E_{aa} \\
  E_i & = & K [ \frac{\chi_{ijkl} + \chi_{kjli} + \chi_{ljik}}{3} - \chi_0 ]^2 \\
  E_{aa} & = & M_1 (\theta_{ijk} - \theta_1) (\theta_{kjl} - \theta_3) + \\
  & & M_2 (\theta_{ijk} - \theta_1) (\theta_{ijl} - \theta_2) + \\
  & & M_3 (\theta_{ijl} - \theta_2) (\theta_{kjl} - \theta_3)
\end{eqnarray*}

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