guesses_any

adcc.guesses_any(matrix, n_guesses, block='s', irrep='A', spin_change=0, spin_block_symmetrisation='none', degeneracy_tolerance=1e-14)

Obtain guesses by inspecting a block of the diagonal of the passed ADC matrix. The symmetry of the returned vectors is already set-up properly. Note that this routine may return fewer vectors than requested in case the requested number could not be found.

matrix The matrix for which guesses are to be constructed n_guesses The number of guesses to be searched for. Less number of

vectors are returned if this many could not be found.

block Diagonal block to use for obtaining the guesses

(typically “s” or “d”).

irrep String describing the irreducable representation to consider. spin_change The spin change to enforce in an excitation.

Typical values are 0 (singlet/triplet/any) and -1 (spin-flip).

spin_block_symmetrisation

Symmetrisation to enforce between equivalent spin blocks, which all yield the desired spin_change. E.g. if spin_change == 0, then both the alpha->alpha and beta->beta blocks of the singles part of the excitation vector achieve a spin change of 0. The symmetry specified with this parameter will then be imposed between the a-a and b-b blocks. Valid values are “none”, “symmetric” and “antisymmetric”, where “none” enforces no particular symmetry.

degeneracy_tolerance

Tolerance for two entries of the diagonal to be considered degenerate, i.e. identical.