(1) Molecular mechanics interfaces, which allow for a variable number of atoms and are labeled
T-MM-D where T = "HO" or "HE" for a homonuclear or heteronuclear potential energy subroutine, respectively, MM stands for "molecular mechanics", and D is the number of analytic derivatives available.
The following molecular mechanics interface is currently standard in POTLIB: HO-MM-0, HO-MM-1.
More interfaces will be added as new potential energy subroutines become available.
(2) Interfaces for a fixed number of atoms. These interfaces are labeled
N-DM where N is the number of bodies, D is the number of analytic derivatives available plus one (e.g., for D = 1, only the potential energy is available, for D = 2, the potential energy and the first derivatives are available), and M is S for scalar mode (i.e., the energy for one geometry is computed per subroutine call, and the geometries, energies, and derivatives (when available) are passed using common blocks) and V for vector mode (i.e., the energies and derivatives (when available) for an array of geometries are calculated per subroutine call and are passed as arguments). Note if D = X, the potential interface is general enough to handle more than one value of D.
The following interfaces for a fixed number of atoms are currently standard in POTLIB: POTLIB-2001, 3-XS, 3-1V, 3-2V, 4-XS, 4-1S, 5-1S, 6-1S, and 7-1S.