## energy_data.nonbonded_sel_atoms — control interaction with picked atoms

> This specifies the number of atoms that must be selected in each nonbonded pair, in order for the energy term to be calculated. Thus, when only a subset of all atoms is used in energy evaluation, this variable controls the interaction between the picked atoms and the rest of the system. When it is `2`, the non-bonded pairs will contain only selected atoms. This means that the optimized atoms will not “feel” the rest of the protein through the non-bonded terms at all.

> If energy_data.nonbonded_sel_atoms is `1` (the default), only one of the atoms in the non-bonded pair has to be a selected atom. This means that the selected region feels the rest of the system through the non-bonded terms, at the expense of longer CPU times.

> See Section 2.2.6 for an example.

> When all atoms are selected, this variable has no effect.