The POTEntial statement allows one to select specific restraining functions for particular classes of distance restraints. By partitioning the distance restraints into particular classes, several restraining functions can be mixed. The total distance restraint energy is a sum over all classes of distance restraints:
where the second sum is carried out over all distance restraints
of the particular class. Each restraint corresponds to exactly one
ASSIgn statement except for the SYMM, 3DPO, and HIGH restraining
functions, where each restraint can comprise groups of ASSIgn statements.