vibeqc.cisd

vibeqc.cisd(h1e_mo, h2e_mo, nelec, norb, n_core=0, nuclear_repulsion=0.0, ms2=None, *, max_excitation=2, nroots=1, max_det=20000)[source]

Run fixed-space CISD on an MO-basis Hamiltonian.

Parameters:

  • h1e_mo ((norb, norb) ndarray) – One-electron Hamiltonian in the MO basis.

  • h2e_mo ((norb, norb, norb, norb) ndarray) – Two-electron integrals, physicist’s notation, MO basis.

  • nelec (int) – Total number of electrons.

  • norb (int) – Total number of spatial orbitals.

  • n_core (int) – Doubly-occupied orbitals frozen out of the correlation treatment. The remaining nelec − 2·n_core electrons are correlated in the upper norb − n_core orbitals; the core enters as a constant energy plus a mean-field dressing of the one-electron term (shared with CASCI).

  • nuclear_repulsion (float) – Nuclear repulsion energy (added to every total energy).

  • ms2 (int, optional) – 2 S_z of the correlated electrons; defaults to (nelec − 2·n_core) % 2 (closed-shell singlet / minimal-spin doublet).

  • max_excitation (int) – 2 for CISD (default), 1 for CIS (reference + singles only).

  • nroots (int) – Number of CI roots to report energies for (default 1; the ground state is root 0).

  • max_det (int or None) – Guard on the determinant-space size.

Return type:

CISDResult