vibeqc.solvers.build_hamiltonian_matrix_unrestricted

vibeqc.solvers.build_hamiltonian_matrix_unrestricted(det_list, h1e, h2e_phys)

Build the full CI Hamiltonian matrix in the unrestricted determinant basis.

Uses a connection map to avoid O(ndet²) all-pairs iteration — only computes matrix elements for determinants connected by ≤ 2 excitations.

Parameters:

• det_list (list[SpinDet]) – List of (alpha_occ, beta_occ) tuples.

• h1e ((norb, norb) ndarray)

• h2e_phys ((norb, norb, norb, norb) ndarray)

Returns:

H – Symmetric Hamiltonian matrix.

Return type:

(ndet, ndet) ndarray