Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0020-7608
    Keywords: MRMP ; multireference-based perturbation theory ; excited states ; polyenes ; excited-state energy gaps ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multireference perturbation theory with complete active space self-consistent field (CASSCF) reference functions is applied to the study of the valence π→π* excited states of 1,3-butadiene, 1,3,5-hexatriene, 1,3,5,7-octatetraene, and 1,3,5,7,9-decapentaene. Our focus was put on determining the nature of the two lowest-lying singlet excited states, 11Bu+ and 21Ag-, and their ordering. The 11Bu+ state is a singly excited state with an ionic nature originating from the HOMO→LUMO one-electron transition while the covalent 21Ag- state is the doubly excited state which comes mainly from the (HOMO)2→(LUMO)2 transition. The active-space and basis-set effects are taken into account to estimate the excitation energies of larger polyenes. For butadiene, the 11Bu+ state is calculated to be slightly lower by 0.1 eV than the doubly excited 21Ag- state at the ground-state equilibrium geometry. For hexatriene, our calculations predict the two states to be virtually degenerate. Octatetraene is the first polyene for which we predict that the 21Ag- state is the lowest excited singlet state at the ground-state geometry. The present theory also indicates that the 21Ag- state lies clearly below the 11Bu+ state in decapentaene with the energy gap of 0.4 eV. The 0-0 transition and the emission energies are also calculated using the planar C2h relaxed excited-state geometries. The covalent 21Ag- state is much more sensitive to the geometry variation than is the ionic 11Bu+ state, which places the 21Ag- state significantly below the 11Bu+ state at the relaxed geometry.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 157-175, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3597-3604 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A relativistic ab initio model potential (AIMP) method with the third-order Douglas–Kroll (DK3) approximation has been developed for the whole series of the actinide elements from Th to Lr. Two different cores, i.e., [Xe, 4f,5d] and [Xe, 4f], have been employed and the corresponding valence basis sets, (14s10p11d9f)/[6s5p5d4f] and (14s10p12d9f)/[6s5p6d4f], are presented for all actinides. The mean absolute errors of the AIMP relative to the all-electron results for the atomic SCF valence orbital energies (ε) and the radial expectation values (〈r〉) are 0.003 (0.001) hartree and 0.004 (0.006) bohr with the small (large) core set. The spectroscopic properties of the 1Σ+ ground state of thorium monoxide, ThO, are calculated at the SCF and complete active space SCF levels. The DK3-AIMP results again satisfactorily reproduce the all-electron DK3 results. The large core set gives almost the same results as the small set for atomic and molecular calculations, suggesting that the 5d electrons can safely be omitted from the valence electrons in actinide chemistry. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Highly accurate relativistic Gaussian basis sets with a finite-nucleus model are developed for the 103 elements from H (Z=1) to Lr (Z=103). The present GTO sets augment the relativistic basis sets with a point-charge model proposed in the first paper of this series. The relativistic third-order Douglas–Kroll approach is adopted in optimizing the orbital exponents of a basis set by minimizing the atomic self-consistent field (SCF) energy. The basis sets are designed to have equal quality and to be appropriate for the incorporation of relativistic effects. The performance of the present basis sets is tested by calculations on a prototypical molecule, gold dimer using SCF and the singles and doubles coupled-cluster model with perturbative triples [CCSD(T)]. Several spectroscopic constants are calculated for the ground state of Au2. At the basis set superposition error (BSSE) corrected CCSD(T) level, the deviation from experiment is ΔRe=0.018 Å, Δωe=−3 cm−1, and ΔDe=−0.17 eV. The finite-size nucleus effect makes Re, ωe, and De smaller by 0.004 Å, 1 cm−1, and 0.05 eV, respectively. The application shows that the present relativistic Gaussian-type orbitals (GTO) basis sets with a finite-nucleus model are accurate and reliable. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2901-2907 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A thorough study on the nature of Mulliken population analysis (MPA) based condensed Fukui function (FF) indices has been performed. It is claimed analytically that nothing can be predicted about the sign of condensed FF indices, even when evaluated by using very small fractional molecular charge (i.e., approximately following the analytical definition of FF indices). The corresponding numerical demonstrations on different chemical systems confirm our claim. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A multireference Møller–Plesset (MRMP) method with a complete active space configuration interaction (CASCI) reference function has been proposed as an accurate and computationally efficient method for treating the ground and excited states of molecules. The CASCI wave function was constructed using the self-consistent field orbitals and used as a reference function of the MRMP to incorporate the remaining dynamical correlation. The advantage in using the CASCI is that it does not require iterations, nor does it encounter convergence difficulties which may be found in complete active space self-consistent field (CASSCF) calculations. The scheme was applied to the potential curves of the ground and low-lying excited states of N2, the potential curve of the ground state of CO, and the vertical valence π–π* excited states of benzene. Excellent agreement between theory, experiment, and some benchmark calculations was obtained. MRMP with CASCI is comparable in accuracy with MRMP with CASSCF. The present scheme will open a possibility toward accurate treatment for the ground and excited states of small to large molecular systems. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8555-8564 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption energies and structures of methanethiolate, SCH3, on the (111) surfaces of Au, Ag, and Cu have been studied using a density functional theory. The results obtained for the Au surface are in good agreement with experiments and previous calculations. The strength of the adsorption energies is found to be Cu〉Ag〉Au, and the nature of the chemisorption bond is discussed. The strong interaction between the SCH3 and Cu surface can be explained in a similar way to that as for the binding energy of SCH3 with metal atoms. Scalar-relativistic effects in the adsorption energies and adsorption structures, which dominate the differences observed between the Ag and Au surfaces, are studied using quasirelativistic and nonrelativistic pseudopotentials. The relativistic effects decrease the adsorption energy of SCH3 on the Au(111) surface, although the binding energy of the AuSCH3 complex is increased by relativity. The unexpected relativistic effects are also discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 6505-6513 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We identified a transversing physical connection between kinetic, exchange, and correlation functionals by using parameter-free (Pfree) exchange and one-parameter progressive (OP) correlation. On the basis of this connection, we investigated how the calculated energies and chemical properties depend on the shape of the functional in the Kohn–Sham scheme. We found that the fundamental conditions of the functionals are connected through Pfree and OP functionals with the exception of a rapidly varying density limit. We also found that the calculated properties are highly affected by the exchange functional shape in particular regions of xσ=|∇ρσ|/ρσ4/3. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A relativistic ab initio model potential (AIMP) for Pt, Au, and Hg atoms has been developed using a relativistic scheme by eliminating small components (RESC) in which the 5p, 5d, and 6s electrons are treated explicitly. The quality of new RESC–AIMP has been tested by calculating the spectroscopic properties of the hydrides of these elements using the Hartree–Fock and coupled cluster with singles and doubles (CCSD) methods. The agreement with reference all-electron RESC calculations is excellent. The RESC–AIMP method is applied successfully in the investigation of the spectroscopic constants of Au2 and Hg2 using the CCSD method with a perturbative estimate of the contributions of triples. The ground state of Pt2 is also determined by RESC–AIMP with the second-order complete active space perturbation method. The results show that scalar relativistic effects on the valence properties are well described by the RESC–AIMP method. The effect on the basis set superposition error on the spectroscopic constants is also examined. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 5216-5223 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction mechanism of Co+ (5F,3F) with H2O has been studied by the ab initio multireference-based theory (MR–SDCI and MC–QDPT) and the density functional theory (B3LYP and BLYP). In the energetics derived by the MR–SDCI(+Q) plus the B3LYP zero-point vibrational energy, the ion–dipole complex, CoOH2+, is initially formed with the binding energy of 38.2 (triplet) and 34.1 (quintet) kcal/mol, which is the most stable complex in the respective potential energy surfaces. Then, Co+ activates one O–H bond of H2O, leading to the insertion complex, HCoOH+. There are three possible dissociation channels from HCoOH+, i.e., →CoOH++H, →CoH++OH, and →CoO++H2. The third dissociation is expected to occur through the transition state of a four-centered structure, with the activation barrier of 61.6 (triplet) and 49.2 (quintet) kcal/mol, although this dissociation has not been detected in the experiment. The ground state of CoO+ is predicted to be 5Δ, and the lowest triplet state is 3Γ with the energy level of 20.8 kcal/mol above. The B3LYP provides the energetics qualitatively similar to the MR–SDCI(+Q) ones through the reactions, with the maximum deviation of 13 kcal/mol. The calculated results are consistent with experimental observations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...