Is there a way/option on the frequency(“ccsd(t)”) function to change the finite difference step, dh? The problem is that I’m getting a low frequency for ethanol that looks a bit suspicious and I would like to analyze the stability of the step, dh, to be sure. I’m using the mode=‘sow’.
You can use
set disp_size XXX
The units are Bohr, and the default value is 0.005.
If that doesn’t help, you can also change the finite difference formula from a 3-point stencil to a 5-point stencil with
set points 5
I tried both methods and they give the same results. The default dh value was actually giving the correct results.