:orphan:
.. index:: *MOLGRD
.. _*MOLGRD:
========
\*MOLGRD
========
The section gives directives for control of a single point evaluation of
the molecular gradient activated with :ref:`PROPERTIES_.MOLGRD` under :ref:`**PROPERTIES`.
The molecular gradient module is usually called from within the geometry
optimization module.
**Advanced options**
.. index:: .TRICK
.. _MOLGRD_.TRICK:
.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.
.. index:: .INTFLG
.. _MOLGRD_.INTFLG:
.INTFLG
-------
Specify what two-electron integrals to include
(default: :ref:`HAMILTONIAN_.INTFLG` under :ref:`**HAMILTONIAN`).
.. index:: .SCREEN
.. _MOLGRD_.SCREEN:
.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**
.. index:: .PRINT
.. _MOLGRD_.PRINT:
.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!
*Default:* Print level :ref:`GENERAL_.PRINT` from :ref:`**GENERAL`.
.. index:: .NUMGRA
.. _MOLGRD_.NUMGRA:
.NUMGRA
-------
Calculate the molecular gradient using numerical differentiation.
*Default:* Analytical evaluation if implemented.