Troubleshooting

It can be advantageous to perform a quick string path at the xTB level and use this as a starting point for the DFT-level string path. This is accessible by defining METHOD = {"kind": "xtb", "model": "gfn0"}.

Below is a sample workflow incorporating this:

1. First, a coarse string is created at the xTB level from initial reactant- and product-like endpoints.
2. Reactant- and product- like string images close to the energy peak are selected and used as inputs for a string at the DFT level, setting n_images to a higher value to produce a finer string.
3. Transition state optimizations are launched from the DFT string images close to the energy peak.

From this point, one would calculate the resulting hessian and normal modes to verify the transition state character of the geometry.