Thank you very much for the detailed answer.
You are right, formic acid has 9 vibrational modes. However, due to the symmetry of the molecule, the Duschinsky matrix for this vibronic transition is block diagonal with two blocks, one of dimension 7x7 (totally symmetric block) and the other with dimension 2x2 (non-totally symmetric block). If the overall shape of the spectrum is dominated by the totally symmetric block you can neglect the other two modes.
Makes sense. For the data I use, however, it doesn’t look like there is a 7x7 totally symmetric block (data is included below). Would a non-symmetric Duschinsky matrix cause issues in the back-end?
1- The vibronic spectrum you want to simulate corresponds to the photoelectron emission of formic acid. So, you need to compute the vibrational modes of the ground states of the neutral and positively charged molecule in order to create the input data for the GBS simulations.
That is what we do. However, we are relaxing the geometry of the excited state to avoid imaginary frequencies. Is this something you do too?
As for points 2-3, we do a Hartree-Fock-type calculation with the basis set being TZV or similar to 6-311+G**. However, we don’t expect the spectrum to be radically different; peaks may shift but the overall shape should be similar.
4- Assuming correctness of points 1-3, how many samples are you taking to reconstruct the vibronic spectrum?
In the spectrum shown in the last post, there are exactly 4675 samples. Referring to the vibronic spectra tutorial, it seems that with 10 samples you can already find the main peaks of the spectrum, pointing towards the fact that 4675 samples is more than enough to recover the overall shape.
Moreover, using a conventional method, we were able to use the same data and compute a spectrum that is approximately correct, compared to experimental data.
This may indicate that I’m simply not using Strawberry Fields correctly. Thus, I’m including the code used to run the simulation along with the data files.
I’d very much appreciate if you could help me fix this issue.
test.py (952 Bytes) formicAcidHF_Hess.txt (122.4 KB) formicAcidCationHF_Hess.txt (125.0 KB)