modified_transition_moments.py

#!/usr/bin/env python3
## vi: tabstop=4 shiftwidth=4 softtabstop=4 expandtab
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## Copyright (C) 2019 by the adcc authors
##
## This file is part of adcc.
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## it under the terms of the GNU General Public License as published
## by the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## GNU General Public License for more details.
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## You should have received a copy of the GNU General Public License
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## ---------------------------------------------------------------------
import libadcc

from .AdcMatrix import AdcMatrix
from .AdcMethod import AdcMethod
from .AmplitudeVector import AmplitudeVector

from libadcc import LazyMp


def compute_modified_transition_moments(gs_or_matrix, dipole_operator,
                                        method=None):
    """Compute the modified transition moments (MTM) for the provided
    ADC method with reference to the passed ground state and
    the appropriate dipole integrals in the MO basis.

    Parameters
    ----------
    gs_or_matrix
        The MP ground state or ADC matrix for which level of theory
        the modified transition moments are to be computed

    dipole_operator: OneParticleOperator
        Electric dipole operator

    method: optional
        Provide an explicit method to override the automatic selection.
        Only required if LazyMp is provided as gs_or_matrix

    Returns
    -------
    adcc.AmplitudeVector
    """
    if isinstance(gs_or_matrix, AdcMatrix):
        ground_state = gs_or_matrix.ground_state
        if method is None:
            method = gs_or_matrix.method
        elif not isinstance(method, AdcMethod):
            method = AdcMethod(method)
    elif isinstance(gs_or_matrix, LazyMp):
        ground_state = gs_or_matrix
        if method is None:
            raise ValueError("A method must be provided if only LazyMp object"
                             " is supplied.")
        elif not isinstance(method, AdcMethod):
            method = AdcMethod(method)
    else:
        raise TypeError("gs_or_matrix should be a LazyMp or AdcMatrix object.")
    if not isinstance(dipole_operator, libadcc.OneParticleOperator):
        raise TypeError("dipole_operator should be "
                        "libadcc.OneParticleOperator.")

    if method.is_core_valence_separated:
        raise NotImplementedError("compute_modified_transition_moments "
                                  "not implemented for CVS")

    mtm_cpp = libadcc.compute_modified_transition_moments(
        method.name, ground_state, dipole_operator
    )
    return AmplitudeVector(*mtm_cpp.to_tuple())