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NIH: National Institute of Diabetes and Digestive and Kidney Diseases NIH: National Institute of Diabetes and Digestive and Kidney Diseases

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Next: The Explicit Hydrogen-Bond Term Up: Nonbonded Energy Terms Previous: Crystallographic Symmetry Interactions


Non-crystallographic Symmetry Interactions

If strict non-crystallographic symmetry is imposed, the crystal symmetry interactions cannot be computed because of nonequivalent environments (see Chapter 18). Instead, only the interaction between non-crystallographically related molecules is computed using the $f_{VDW}$ and $f_{ELEC}$ functional forms, i.e.,
\begin{displaymath}
E_{PVDW} = \sum_{S{\in}NCS} \sum_{i<j} f_{VDW} (r_{i} - Sr_{j})
\end{displaymath} (4.23)


\begin{displaymath}
E_{PELE} = \sum_{S{\in}NCS} \sum_{i<j} f_{ELEC} (r_{i} - Sr_{j})
\end{displaymath} (4.24)

The atom/group search and the update of the interaction list are carried out analogously to the intramolecular case. (Refer to Chapter 18 for the definition of non-crystallographic symmetry operators.)



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