FanCI tutorial

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FanCI tutorial

Closed this issue 20 days ago · 3 comments

AlexandreDeCamargo commented 5 months ago

After getting from @RichRick1 a FCIDUMP file of a Hubbard model I am getting the values of the cost function, the residuals, the optimality and active_mask equal to zero when optimizing the AP1roG wavefunction. The solution found is:

x: [ 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 3.000e+01]

Optimizing the pCCD+S wave function give me residuals near zero ($10^{-15}$ order) and a solution x:

x: [-1.334e+01 1.334e+01 ... -5.454e-14 3.000e+01]

Answer 1 · 2024-04-15T13:30:57.000Z

@PaulWAyers I gave @AlexandreDeCamargo 6-site Hubbard model with U=10, so it's a strongly correlated system. I'd expect to have much higher projection error
@msricher is there any system for which AP1roG method will give a big error in energy?

Answer 2 · 2024-04-15T13:48:14.000Z

AP1roG should be bad for attractive Hubbard and attractive Richardson.

Answer 3 · 2024-04-16T15:00:26.000Z

I'm not sure. Is it possible to compare against the FCI energy?