Orbital optimization in the density matrix renormalization group, with applications to polyenes and β-carotene
In previous work we have shown that the density matrix renormalization group (DMRG) enables near-exact calculations in active spaces much larger than are possible with traditional complete active space algorithms. Here, we implement orbital optimization with the DMRG to further allow the self-consistent improvement of the active orbitals, as is done in the complete active space self-consistent field (CASSCF) method. We use our resulting DMRG-CASSCF method to study the low-lying excited states of the all-trans polyenes up to C₂₄H₂₆ as well as β-carotene, correlating with near-exact accuracy the optimized complete π-valence space with up to 24 active electrons and orbitals, and analyze our results in the light of the recent discovery from resonance Raman experiments of new optically dark states in the spectrum.
© 2008 American Institute of Physics. Received 13 December 2007; accepted 28 January 2008; published online 11 April 2008. This work was supported by Cornell University, the Cornell Center for Materials Research (CCMR), the David and Lucile Packard Foundation, the National Science Foundation CAREER program CHE-0645380, the Alfred P. Sloan Foundation, and the Department of Energy, Office of Science through Award No. DE-FG02-07ER46432. J.H. would like to acknowledge support provided by a Kekulé Fellowship of the Fond der Chemischen Industrie.
Accepted Version - 0712.2475.pdf
Published - 1_2E2883976.pdf