The seamless continuation from single reference (SR) broken-symmetry (BS) to multi-reference (MR) methods such as the density matrix renormalization group (DMRG) was revisited to elucidate natural orbitals (UNO) and their occupation numbers for iron-sulfur clusters such as P- and FeMoco clusters in nitrogenase. Fractional occupation numbers of UNO for these clusters by SR-BS were consistent with those of open-shell orbitals by MR-DMRG, supporting the UNO-CI calculations of large Fe-S clusters on classical and quantum computers.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry