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+\documentclass[12pt]{article}
+
+\begin{document}
+
+\begin{eqnarray*}
+E_T & = & \sum_i [ E_i^S + \frac{1}{2} \sum_{j \neq i} V_{ij}
+  (r_{ij},q_i,q_j) + E_i^{BB} ] \\
+V_{ij}(r_{ij},q_i,q_j) & = & U_{ij}^R(r_{ij}) + U_{ij}^A(r_{ij},
+  q_i,q_j) + U_{ij}^I(r_{ij},q_i,q_j) + U_{ij}^V(r_{ij}) \\
+\end{eqnarray*}                           
+
+\end{document}
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+\documentclass[12pt]{article}
+
+\begin{document}
+
+\begin{eqnarray*}
+U_{ij}^R(r_{ij}) & = & f_{S_{ij}} A_{ij} \exp (-\lambda_{ij} r_{ij}) \\
+U_{ij}^A(r_{ij},q_i,q_j) & = & -f_{S_{ij}} b_{ij} B_{ij} \exp (-\alpha_{ij} r_{ij}) \\
+U_{ij}^I(r_{ij},q_i,q_j) & = & J_{ij} (r_{ij}) q_i q_j \\
+U_{ij}^V(r_{ij}) & = & f_{L_{ij}} (C_{VDW_i}C_{VDW_j})^\frac{1}{2}/r_{ij}^6 \\
+\end{eqnarray*}                           
+
+\end{document}
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