New answers tagged ab-initio-calculations
8
Just like geometry optimization, there is no practical way to be 100% sure that you have the global minimum of SCF solutions.
But there are checks you can do to make sure that the SCF solution you got is a reasonable minimum. One of them is checking the electronic hessian at the SCF solution and determining the lowest eigenvalues. If one or more negative ...
10
You're right about the ability to change the initial guess repeatedly until you get the lowest energy, and this is how it's done in software like MOLPRO which don't offer "stability analysis".
However in software like GAUSSIAN and CFOUR, you can do something called stability analysis, which is described for example in the GAUSSIAN documentation ...
6
Rather than starting with a single-determinant (single-reference) such as the Hartree-Fock determinant which is obtained by an HF-SCF calculation, multi-reference methods such as MRCI, MR-ACPF, MR-AQCC, and even MR-CC will start with a multi-configurational SCF (MCSCF) calcualtion. There's many types of these, and many can be found here: What are the types ...
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