Balancing single- and multi-reference correlation in the chemiluminescent reaction of dioxetanone using the anti-Hermitian contracted Schroedinger equation

Journal Article · Sat May 07 00:00:00 EDT 2011 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3585691· OSTI ID:21560202

Greenman, Loren; Mazziotti, David A ^[1]

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1. Department of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States)

Direct computation of energies and two-electron reduced density matrices (2-RDMs) from the anti-Hermitian contracted Schroedinger equation (ACSE) [D. A. Mazziotti, Phys. Rev. Lett. 97, 143002 (2006)], it is shown, recovers both single- and multi-reference electron correlation in the chemiluminescent reaction of dioxetanone especially in the vicinity of the conical intersection where strong correlation is important. Dioxetanone, the light-producing moiety of firefly luciferin, efficiently converts chemical energy into light by accessing its excited-state surface via a conical intersection. Our previous active-space 2-RDM study of dioxetanone [L. Greenman and D. A. Mazziotti, J. Chem. Phys. 133, 164110 (2010)] concluded that correlating 16 electrons in 13 (active) orbitals is required for realistic surfaces without correlating the remaining (inactive) orbitals. In this paper we pursue two complementary goals: (i) to correlate the inactive orbitals in 2-RDMs along dioxetanone's reaction coordinate and compare these results with those from multireference second-order perturbation theory (MRPT2) and (ii) to assess the size of the active space--the number of correlated electrons and orbitals--required by both MRPT2 and ACSE for accurate energies and surfaces. While MRPT2 recovers very different amounts of correlation with (4,4) and (16,13) active spaces, the ACSE obtains a similar amount of correlation energy with either active space. Nevertheless, subtle differences in excitation energies near the conical intersection suggest that the (16,13) active space is necessary to determine both energetic details and properties. Strong electron correlation is further assessed through several RDM-based metrics including (i) total and relative energies, (ii) the von Neumann entropy based on the 1-electron RDM, as well as the (iii) infinity and (iv) squared Frobenius norms based on the cumulant 2-RDM.

• OSTI ID: 21560202
• Journal Information: Journal of Chemical Physics, Vol. 134, Issue 17; Other Information: DOI: 10.1063/1.3585691; (c) 2011 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
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PHYSICAL AND ANALYTICAL CHEMISTRY
CALCULATION METHODS
CHEMILUMINESCENCE
COMPARATIVE EVALUATIONS
COORDINATES
DENSITY MATRIX
ELECTRON CORRELATION
ELECTRONS
ENTROPY
EXCITATION
LUCIFERIN
PERTURBATION THEORY
SCHROEDINGER EQUATION
SURFACES
VISIBLE RADIATION
ALBUMINS
CORRELATIONS
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EMISSION
ENERGY-LEVEL TRANSITIONS
EQUATIONS
EVALUATION
FERMIONS
LEPTONS
LUMINESCENCE
MATRICES
ORGANIC COMPOUNDS
PARTIAL DIFFERENTIAL EQUATIONS
PHOTON EMISSION
PHYSICAL PROPERTIES
PROTEINS
RADIATIONS
THERMODYNAMIC PROPERTIES
WAVE EQUATIONS