Position Constraints

Atomic positions are constrained with the active, nzinactive and inactive terms. When an atom is inactive it only enters into potential and force calculations which use at least one active atom. For example when two atoms are bonded, calculations are only performed when one is active. The force on the inactive atoms is by definition zero and inactive atoms cannot be moved within AMMP. The command nzinactive differentiates between atoms which have coordinates and those which dont. Nzinactive will force atoms with x,y,z not equal to 0.,0.,0 to be inactive, while leaving atoms positioned at 0.,0.,0 as active. This is useful for completing partial structures.

active low_atom high_atom ; activates atoms between low_atom and high_atom (removes the constraints).

inactive low_atom high_atom; applies constraints to all atoms between low_atom and high_atom.

nzinactive low_atom high_atom; applies constraints to atoms not at 0.,0.,0.

high_atom is optional, for example active 100; activates only atom 100.