The default converger in the SCF calculation is to be replaced by Pulay's procedure [48] as soon as the density matrix is sufficiently stable.   A considerable improvement in speed can frequently be achieved by the use of PULAY, particularly for excited states. If a large number of SCF calculations are envisaged, a sample calculation using 1SCF and PULAY should be compared with using 1SCF on its own, and if a saving in time results, then PULAY should be used in the full calculation. PULAY should be used with care in that its use will prevent the combined package of convergers (SHIFT, PULAY and the CAMP-KING convergers) from being used automatically in the event that the system fails to go SCF in (ITRY-10) iterations.

PULAY does not work with MOZYME

The combined set of convergers very seldom fails.