The gradient norm in kcals/mol/Ångstrom is less than
TOLERG multiplied by the square root of the number of coordinates to be
optimized.

Exceptions:

If GNORM is specified, TOLERG=n.nnn divided by the square
root of the number of coordinates to be optimized, and the secondary tests are
not done. If LET is not specified, n.nnn is reset to 0.01, if it was
smaller than 0.01.

The calculated heats of formation on two successive cycles
differ by less than TOLERF.

Exception:

If GNORM is specified, the TOLERF test is not used.

Secondary tests:

For the TOLERG, TOLERF, and TOLERX tests, a second
test in which no individual component of the gradient should be larger than
TOLERG must be satisfied.

Other tests:

If, after the TOLERG, TOLERF, or TOLERX test has been
satisfied three consecutive times the heat of formation has dropped by less
than 0.3kcal/mol, then the optimization is stopped.