PRFO not suitable for larger systems ?

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helloworld
PRFO not suitable for larger systems ?

The documentation says that "P-RFO is a conventional transition state optimisation algorithm which involves a full Hessian calculation to find the transition state mode to follow. It is therefore only suitable for the optimisation of small molecules."

So it cannot be used at all for larger systems like mine ? with total atoms as 20,000+ , qm region ~32 atoms and active region around 1000 atoms ?

Thank you so much,

tomkeal
tomkeal's picture
PRFO not suitable for larger systems ?

That's right - with 1000 active atoms, assuming you're calculating the initial Hessian by finite difference, you're looking at a minimum of 3000 energy evaluations before the optimisation starts.

You could get away with it by reducing the active region to the size of the QM region, but this may not give you the answer you're looking for.

A much better solution is to use the dimer method, which is designed to avoid having to calculate a Hessian matrix and so is more suitable for large systems.

Another option is to use microiterative optimisation, but this is more complicated to set up so I would suggest trying the standard dimer method first.

Tom

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