In Guassian, which convergence algorithm is best for working with transition metal interaction? It is taking a long time to even get the first block of coordinates, in the output file it said to use the steepest-descent method, but I think maybe this is not enough. I read that in Orca there is the KDIIS algorithm to enable faster convergence for transitional metals, is there something similar in Gaussian?
I tried scf=qc and scf=xqc and it does not work for the interaction between graphene and a transition metal cluster.
The main problem seems not to be due to the algorithm, but to the multireference nature of some transition metal compounds that renders the SCF and the PES rather unreliable. DFT has a lot of problems to describe such systems and that is a physical limitation of the theory.
I'd say that you can't employ DFT on transition metals without some critical thinking, that is a core discussion in the inorganic modelling and you can find references and discussion on it almost everywhere. I'm not sure of what can or can not be done in terms of convergence algorithm, since I believe we should develop more into the multireference methods.
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