Hi,

I would like to ask if it is possible to get Numerical Frequencies by doing a double displacement across each direction.

That is, 2 points in negative and 2 points in positive displacement.

I have some rather difficult cases , where the potential energy surface is really flat and as a result I get imaginary frequencies.

However, if i perform analytical frequencies, I don't get any imaginary numbers.

I tried giving a smaller step size, increasing the $scfconv criteria, adding the $denconv and the weight derivatives options in the control, but it did not always help.

The problem is that the system is huge and aoforce takes forever .

I am only interested in the vibrations of my guest molecule, so i can ignore the vibrations from the host material.

Has it been implemented in NumForce ? is there any 'secret' and non-documented keyword ?

any hints are welcome.

Thank you,

Andreas