Hello Harpal ..

Setting Options: The IOp keyword lets you assign integer values to specific options.

Overlay Control: Each overlay in Gaussian 16 has numbered options, and these options remain unchanged throughout execution within that overlay.

Archiving: When using the IOp keyword, archiving is disabled. This means that the calculation won’t be archived due to the arbitrary effects that setting internal options can have.

Route Section: Explicitly set IOp values in the route section are not passed on to the second and subsequent automatically-generated job steps. For multi-step methods or combinations like optimization and frequency calculations, use options specific to those keywords instead of explicit IOp values.

You can discuss the work related to Gaussian projects with the MolQube team.

Their email address: [email protected]

Best regard.