I am trying to do geometry optimization of hydrogen fluoride using a very large basis set (cc-pV6Z). Calculations at the CCSD level take much longer than ate the CCSD(T) one, even though that latter is formally more demanding (~N7 instead of ~N6). The reason for this is the analytical gradient procedure used by default in Gaussian. I would like to use numerical gradients, which in this case prove to be a much faster algorithm. Nonetheless, I do not know how to tell Gaussian to give up in its defaults and do what I want it to do :) Please, help me on this.
Best reagrds!
Marcin
I ran into almost exactly the same problem, and I think the only way to do this is to set up for a CCSD(T) calculation, then turn off non-iterative corrections via iop(9/14=0).
- Badges
- Science topic