quemb.molbe.helper.get_frag_energy

quemb.molbe.helper.get_frag_energy(mo_coeffs, nsocc, nfsites, efac, TA, h1, rdm1, rdm2s, dname, veff0=None, veff=None, use_cumulant=True, eri_file='eri_file.h5')

Compute the fragment energy.

This function calculates the energy contribution of a fragment within a larger molecular system using the provided molecular orbital coefficients, density matrices, and effective potentials.

Parameters:

  • mo_coeffs (ndarray) – Molecular orbital coefficients.

  • nsocc (int) – Number of occupied orbitals.

  • nfsites (int) – Number of fragment sites.

  • efac (list) – List containing energy scaling factors and indices.

  • TA (ndarray) – Transformation matrix.

  • h1 (ndarray) – One-electron Hamiltonian.

  • rdm1 (ndarray) – One-particle density matrix.

  • rdm2s (ndarray) – Two-particle density matrix.

  • dname (str) – Dataset name in the HDF5 file.

  • veff0 (ndarray) – veff0 matrix, the original hf_veff in the fragment Schmidt space

  • veff (ndarray) – veff for non-cumulant energy expression

  • use_cumulant (bool) – Whether to return cumulant energy, by default True

  • eri_file (str, optional) – Filename of the HDF5 file containing the electron repulsion integrals. Defaults to ‘eri_file.h5’.

Returns:

List containing the energy contributions: [e1_tmp, e2_tmp, ec_tmp].

Return type:

list