# *MOLGRD¶

The section gives directives for control of a single point evaluation of
the molecular gradient activated with *.MOLGRD* under ***PROPERTIES*.

The molecular gradient module is usually called from within the geometry optimization module.

**Advanced options**

## .TRICK¶

If activated the calculation of the SL and SS two-electron integral contributions to the gradient is skipped if their contribution is estimated to be small. An “empirical” estimate of the norms of the LS and SS two-electron gradients based on the norm of the LL two-electron gradient. If deactivated all contributions to gradient are calculated and if activated then only “necessary” contributions are calculated.

*Default:* Deactivated.

## .INTFLG¶

Specify what two-electron integrals to include
(default: *.INTFLG* under ***HAMILTONIAN*).

## .SCREEN¶

Screening threshold.

*Default:*

```
.SCREEN
1.0D-17
```

Which means that screening is turned off by default. This is due to an enormous demand of memory.

**Programmers options**

## .PRINT¶

Print level.

A print level of less than 3 gives only the total gradient. Print levels from 3+ gives individual contributions to the gradient (kinetic energy gradient, nuclear attraction gradient etc.). Print levels of 5+ print some matrices, and 10+ give massive output!

## .NUMGRA¶

Calculate the molecular gradient using numerical differentiation.

*Default:* Analytical evaluation if implemented.