quemb.molbe.solver.solve_uccsd

quemb.molbe.solver.solve_uccsd(mf, eris_inp, frozen=None, relax=False, use_cumulant=True, rdm2_return=False, rdm_return=False, verbose=0)

Solve the U-CCSD (Unrestricted Coupled Cluster with Single and Double excitations) equations.

This function sets up and solves the UCCSD equations using the provided mean-field object. It can return the one- and two-particle density matrices and the UCCSD object.

Parameters:

  • mf (UHF) – Mean-field object from PySCF. Constructed with make_uhf_obj

  • eris_inp – Custom fragment ERIs object

  • frozen (list or int, optional) – List of frozen orbitals or number of frozen core orbitals. Defaults to None.

  • relax (bool, optional) – Whether to use relaxed density matrices. Defaults to False.

  • use_cumulant (bool, optional) – Whether to use cumulant-based energy expression. Defaults to True.

  • rdm2_return (bool, optional) – Whether to return the two-particle density matrix. Defaults to False.

  • rdm_return (bool, optional) – Whether to return the one-particle density matrix. Defaults to False.

  • verbose (int, optional) – Verbosity level. Defaults to 0.

Returns:

  • ucc (pyscf.cc.ccsd.UCCSD): UCCSD object

  • rdm1 (tuple, numpy.ndarray, optional): One-particle density matrix

    (if rdm_return is True).

  • rdm2 (tuple, numpy.ndarray, optional): Two-particle density matrix

    (if rdm2_return is True and rdm_return is True).

Return type:

tuple