# Geometric optimization criteria

### GNORM "RMS GRADIENT = n.nn IS LESS THAN CUTOFF = m.mm"

Defined in:
EF
Default value:
1.0
Basic test:
The calculated GNORM is less than that defined by GNORM .

### TOLERX "Test on X Satisfied"

Defined in:
FLEPO

Default value:
0.0001 Ångstroms
Basic test:
The projected change in geometry is less than TOLERX Ångstroms.
Exception:
If GNORM is specified, the TOLERX test is not used.

### DELHOF "Herbert's Test Satisfied"

Defined in:
FLEPO
Default value:
0.001
Basic test:
The projected change in geometry is less than DELHOF kcals/mol.
Exception:
If GNORM  is specified, the DELHOF test is not used.

### TOLERG "Test on Gradient Satisfied"

Defined in:
FLEPO
Default value:
1.0
Basic test:
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.
• If PRECISE is specified, TOLERG=0.2

### TOLERF "Heat of Formation Test Satisfied"

Defined in:
FLEPO
Default value:
0.002 kcal/mol
Basic test:
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.

### TOL2

Defined in:
POWSQ
Default value:
0.4
Basic test:
The absolute value of the largest component of the gradient is less than TOL2
Exceptions:

• If  PRECISE is specified, TOL2=0.01
• If GNORM  is specified, TOL2=n.nn
• If LET is not specified, TOL2 is reset to 0.01, if n.nn was smaller than 0.01.

### TOLS1

Defined in:
NLLSQ
Default value:
0.000 000 000 001
Basic test:
The square of the ratio of the projected change in the geometry to the actual geometry is less than TOLS1.
Name:
<none>
Defined in:
NLLSQ
Default value:
0.2
Basic test:
Every component of the gradient is less than 0.2.