Frequency calculation extremely slow

1

I’m wondering if there is a way to speed up the vibrational analysis.
I am running a frequency calculation on a molecule containing 52 atoms for which 307 displacements are needed.
I am running the calculation on 16CPUs and 16GB memory.
The calculation run using Gaussian16 on 8CPU takes roughly 4-5h for optimization and frequency analysis but with these settings, the frequency analysis only in PSI4 1.7 using a pre-optimized structure takes more than 2 days to complete!
For both software I am running calculations at the M06-2X / Def2-SVP level of theory.

The input I’m using is the following:

memory 16 gb

molecule dummy {
0 1
*coordinates*
}

set {
    basis Def2-SVP
}

wfn = frequency('M06-2X' , return_wfn=True)
wfn.to_file('dummy_wfn')

Is there any trick to speed the process or it is a limitation in PSI4?
For a few conformers it seems very impractical to run vibrational analyses here…

Thanks for the help!

2

PS: The molecule contains only C, H, and O atoms

3

Not realistically, no.

The heart of the problem is that we (the developers) need to implement analytic hessians for more DFT functionals. This is a project I’d love to work on, but time is not permitting.

4

Thanks for the note! It makes sense. I have checked a bit myself and I understand that although feasible it may not be a priority.

To have analytic heassians for DFT would surely expand the applicability of PSI4 for QM studies on chemical reactions mechanisms where thermochemistry analysis is definitively required.

I hope someone will take this ‘maybe not so exciting’ task!

5

Expanding our DFT hessian and TD-DFT capabilities[1] is item #2 on my Psi development priority list. The problems are that #1 (an overhaul of our decades-old I/O system) is going to take a lot of time, and that I’m trying to finish up some research projects and a grant proposal first.

[1] = There are three “parts” of the Hartree-Fock hessian code that need to be adapted for DFT. There’s the orbital second derivative, the orbital-geometry mixed derivative, and the geometry second derivative. The orbital second derivative part is also needed by TD-DFT, which doesn’t need any other special technology. So getting TD-DFT working is not only simpler than getting DFT hessians, but it’s an excellent correctness test of one of the three major pieces. For those reasons, getting TD-M06-2X is an important stepping stone to getting M06-2X hessians. Incidentally, the path that I foresee is UKS LDA hessians → UKS GGA hessians → RKS GGA hessians → TD-UKS Meta → TD-RKS Meta → UKS Meta hessians → RKS Meta hessians

6

Definitively! Thanks for the update and for the help - very very appreciated!