Those making the greatest contribution to the energy are changed in order to make the energy fall. The energy is again calculated. The structure is then said to be optimized. It is frequently necessary to optimize several different conformations to get a realistic idea of which is the lowest energy conformation of the molecule. DTMM also includes a very unusual feature in its calculations where it treats a group of atoms as a fragment so that it can rotate the fragment in an effort to locate local minima.
Molecular mechanics requires lots of known values to be recognised.
These are put into the program as parameters . These values include equilibrium bond lengths, equilibrium bond angles, force constants, and torsion angle degeneracies for rotatable bonds. For parameters to be correlated to the molecule each atom must have a type. Most programs require you to specify this. For instance, a carbon would be recognized as a sp3 hybridized carbon if it has four explicit substituents.