This score is derived from the number of pairs of atoms in the PDB_model_num that are unusually close to each other.
It is calculated by the MolProbity pdbx_vrpt_software and expressed as the number or such clashes per thousand atoms.
For structures determined by NMR the clashscore value here will only consider label_atom_id pairs in the
well-defined (core) residues from ensemble analysis.