Second-order perturbation theory with complete and restricted active space reference functions applied to oligomeric unsaturated hydrocarbons

Shahi, Abdul Rehaman Moughal; Cramer, Christopher J.; Gagliardi, Laura

doi:10.1039/b912607d

Cited by 42 publications

(46 citation statements)

References 72 publications

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“…Available CASPT2 calculations give excitation energies in the range 6.1−6.3 eV, 3,14,18 but these single-state studies are hard to compare as they employ different zero-order Hamiltonians 14,18 or, in the presence of diffuse functions, lead to a too diffuse state due to the lack of a multistate treatment of the close Rydberg state. 3 Various flavors of CC calculations yield values between 6.2 and 6.4 eV.…”

Section: Introductionmentioning

confidence: 99%

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Daday

Smart

Booth

et al. 2012

J. Chem. Theory Comput.

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We employ the recently developed full configuration interaction quantum Monte Carlo (FCIQMC) method to compute the π → π* vertical excitation energies of ethene and all-trans butadiene. These excitations have been the subject of extensive theoretical studies, and their location with respect to the corresponding absorption band maximum is the source of a long lingering debate. Here, we reliably estimate the vertical excitations of ethene and butadiene by performing FCIQMC calculations for spaces as large as 10(18) and 10(29) Slater determinants, respectively. For ethene, we obtain a vertical excitation energy in the range 7.89-7.96 eV, depending on the particular equilibrium ground-state geometry employed, and definitely higher than the absorption maximum located at 7.66 eV. For the computationally more challenging case of butadiene, our calculations provide a robust estimate of about 6.3 eV for this excitation, that is, 0.4 eV higher than the corresponding absorption band maximum. Our FCIQMC excitation energies represent a reliable benchmarking reference for future calculations.

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Section: Introductionmentioning

confidence: 99%

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Daday

Smart

Booth

et al. 2012

J. Chem. Theory Comput.

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“…15 They ascribed the ordering anomaly to the electron correlation effects. Since then, there have been continuous and considerable investigations, such as by Tavan and Schulten, 16 Cave and Davidson, 17 Nakayama et al, 18 Hsu et al, 19 Serrano-Andres et al, 20 Starcke et al, 21 Marion and Gilka, 22 Shahi et al, 23 in calculating the 2A g /1B u orderings for the short unsubstituted polyene and Shukla 24 for the substituted polyene [poly(diphenylacetylene)]. It is found that the 2A g state has important contributions from electron double excitation configuration in the molecular orbital picture.…”

Section: Introductionmentioning

confidence: 99%

Theoretical predictions of red and near-infrared strongly emitting X-annulated rylenes

Peng

Niu

Wang

et al. 2011

The Journal of Chemical Physics

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The optical properties of rylenes are extremely interesting because their emission colors can be tuned from blue to near-infrared by simply elongating the chain length. However, for conjugated chains, the dipole-allowed odd-parity 1B u excited state often lies above the dipole-forbidden evenparity 2A g state as the chain length increases, thus preventing any significant luminescence according to Kasha's rule. We systemically investigated the 1B u /2A g crossover behaviors with respect to the elongating rylene chain length with various quantum chemistry approaches, such as timedepended density functional theory (TDDFT), complete active space self-consistent field theory (CASSCF/CASPT2), multireference configuration interaction (MRCI)/Zerner's intermediate neglect of diatomic overlap (ZINDO), and MRCI/modified neglect of differential overlap. The calculated results by CASSCF/CASPT2 and MRCI/ZINDO are completely coherent: the optical active 1B u state lies below the dark B 3g or 2A g state for perylene and terrylene, which results in strong fluorescence; while a crossover to S 1 = 2A g occurs and leads to much weaker fluorescence for quaterrylene. Then we put forward a molecular design rule on how to recover fluorescence for the longer rylenes by introducing heteroatom bridges. Several heteroatom-annulated rylenes are designed theoretically, which are predicted to be strongly emissive in the red and near-infrared ranges. These are further confirmed by theoretical emission spectra as well as radiative and nonradiative decay rate calculations by using the vibration correlation function formalisms we developed earlier coupled with TDDFT.

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“…[40][41][42][43][44][45] To address this issue, a second-order perturbation method (ORMAS+PT2) is under development.…”

Section: Discussionmentioning

confidence: 99%

ORMAS-SCF Study of Silicon (100) Surface Clusters^†

Roskop¹,

Gordon²

2010

J. Phys. Chem. A

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An occupation restricted multiple active space (ORMAS) study of clusters that represent the silicon(100) surface (up to nine surface dimers) is discussed. The accuracy of three different active orbital ORMAS partition schemes for Si(100) surface clusters are compared. In addition to ORMAS-SCF calculations, generalized valence bond-perfect pairing (GVB-PP) properties are generated for comparison purposes. The ability of ORMAS to generate a reliable multiconfigurational zeroth-order wave function is systematically tested and when possible is compared to the full complete active space self-consistent field (CASSCF) method. This provides good benchmarks for the accuracy of ORMAS compared to CASSCF. It is demonstrated that ORMAS consistently provides a high degree of accuracy with a significantly reduced computational effort relative to a CASSCF calculation. For the largest cluster, for which a full CASSCF calculation is not possible, ORMAS predicts that the Si(100) surface dimers are symmetric. Department of Chemistry, Iowa State UniVersity, Ames Iowa 50010ReceiVed : February 28, 2010; ReVised Manuscript ReceiVed: April 21, 2010 An occupation restricted multiple active space (ORMAS) study of clusters that represent the silicon(100) surface (up to nine surface dimers) is discussed. The accuracy of three different active orbital ORMAS partition schemes for Si(100) surface clusters are compared. In addition to ORMAS-SCF calculations, generalized valence bond-perfect pairing (GVB-PP) properties are generated for comparison purposes. The ability of ORMAS to generate a reliable multiconfigurational zeroth-order wave function is systematically tested and when possible is compared to the full complete active space self-consistent field (CASSCF) method. This provides good benchmarks for the accuracy of ORMAS compared to CASSCF. It is demonstrated that ORMAS consistently provides a high degree of accuracy with a significantly reduced computational effort relative to a CASSCF calculation. For the largest cluster, for which a full CASSCF calculation is not possible, ORMAS predicts that the Si(100) surface dimers are symmetric.

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Second-order perturbation theory with complete and restricted active space reference functions applied to oligomeric unsaturated hydrocarbons

Cited by 42 publications

References 72 publications

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Theoretical predictions of red and near-infrared strongly emitting X-annulated rylenes

ORMAS-SCF Study of Silicon (100) Surface Clusters^†

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Second-order perturbation theory with complete and restricted active space reference functions applied to oligomeric unsaturated hydrocarbons

Cited by 42 publications

References 72 publications

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Full Configuration Interaction Excitations of Ethene and Butadiene: Resolution of an Ancient Question

Theoretical predictions of red and near-infrared strongly emitting X-annulated rylenes

ORMAS-SCF Study of Silicon (100) Surface Clusters†

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Product

Resources

About

ORMAS-SCF Study of Silicon (100) Surface Clusters^†