[Mpqc-users] evaluating energy of wavefunction, without scf optimization

[Toon V. <Too...@UG...>]

Hi,

This might be a bizarre question, but I am interested in a simple way to
calculate e.g. the HF energy/gradient/whatever of a wavefunction
optimized with DFT/B3LYP. My interest is not restricted to these two
levels of theory, but any combination of one-body wavefunction methods.
I currently tried a simple approach, but ran into a few difficulties:

* first calculate a the wavefunction with method A, e.g. with water1.in:

% Single point calculation
mpqc:(
  mole<CLKS>:(
    basis<GaussianBasisSet>:(
      molecule = $:molecule
      name = "3-21G*"
    )
    molecule = $:molecule
    functional<StdDenFunctional>:(
      name = "B3LYP"
    )
    guess_wavefunction<CLHF>:(
      total_charge = 0
      molecule = $:molecule
      basis<GaussianBasisSet>:(
        molecule = $:molecule
        name = "STO-3G"
      )
    )
    total_charge = 0
  )
)
molecule<Molecule>:(
  geometry = [
    [ -0.0073905643625 0.0261284427758 0.00708466177419 ]
    [ 1.95058386069 -0.0137957715056 0.0492585954974 ]
    [ -0.0469159377498 1.84102313597 0.0546961383553 ]
  ]
  atoms = [ "O" "H" "H" ]
)

* Then run a second calculation with method B, using this input file:

% Single point calculation
mpqc:(
  do_gradient = "yes"
  mole<CLKS>:(
    maxiter=0
    basis<GaussianBasisSet>:(
      molecule = $:molecule
      name = "3-21G*"
    )
    molecule = $:molecule
    functional<StdDenFunctional>:(
      name = "BP86"
    )
    guess_wavefunction="water1.wfn"
    total_charge = 0
  )
)
molecule<Molecule>:(
  geometry = [
    [ -0.0073905643625 0.0261284427758 0.00708466177419 ]
    [ 1.95058386069 -0.0137957715056 0.0492585954974 ]
    [ -0.0469159377498 1.84102313597 0.0546961383553 ]
  ]
  atoms = [ "O" "H" "H" ]
)


The maxiter=0 option does not work (tested with a recent cvs checkout).
This is no surprise since not too many people actually need this. Is
there a proper alternative for this trick? Any help will be appreciated.

best regards,

Toon