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.