During a MOZYME run, the steady accumulation of small errors (for example,
roundoff, and more important, the elimination of atoms from LMOs) will
result in the LMOs becoming non-orthogonal. These errors can be eliminated
almost completely by re-orthogonalizing the LMOs. If REORTH
is present, then the LMOs will be re-orthogonalized at the end of every 10th SCF
calculation, starting with the first SCF.
In practice, a better strategy is to allow the job to run for ~500 cycles or
1-2 CPU days, then shut it down and restart it using
RESTART, but without using keyword OLDENS.
That will cause the LMO's to be recalculated, and job to resume starting with
the geometry at the end of the previous run.