PRECISE 

Description

The criteria for terminating all optimizations (both electronic and geometric) will be increased by a factor of 10. This keyword should be used in most cases and only left out if the calculation is encountering difficulty converging in either geometry or SCF. If the results are going to be used in a FORCE, LTRD, or IRC calculation, where the geometry needs to be known to a high degree of accuracy, then specification of PRECISE is very strongly recommended. As well as increasing convergence criteria, PRECISE also requires more accurate determination of all numerical derivatives by use of a central finite difference rather than a forward finite difference algorithm.

See also:

FORCE, LTRD, IRC