Hiroko Moriyama

Chukyo University, Koromo, Aichi, Japan

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Publications (12)29.8 Total impact

  • The Journal of Chemical Physics 03/2014; 140(12):129904. · 3.12 Impact Factor
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    ABSTRACT: We studied the ground and excited states of CeO using the restricted active space CI method in the energy range below 25 000 cm(-1). Energy levels are computed to within errors of 2700 cm(-1). Electron correlation effects arising from the ionic core composed of Ce 5s, 5p, 4f(∗), 5d(∗), and O 2s, 2p spinors play crucial role to CeO spectra, as well as correlation effects of electrons distributed in the valence Ce 4f, 5d, 6s, and 6p spinors. Here, 4f(∗) and 5d(∗) denote spinors expanded to describe electron polarization between Ce and O. A bonding mechanism is proposed for CeO. As the two separate atoms in their ground states, Ce (4f (1)5d(1)6s(2)) (1)G4 and O (2s(2)2p(4)) (3)P2, approach each other, a CeO(2+) core is formed by two-electron transfer from Ce 5d, 6s to O 2p. Inside this ellipsoidal ion, a valence bond between Ce 5p and O 2s and an ionic bond between O 2p and Ce 5p are formed with back-donation through Ce 4f(∗) and 5d(∗).
    The Journal of Chemical Physics 06/2013; 138(22):224310. · 3.12 Impact Factor
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    ABSTRACT: The electronic structure of the EuF molecule is investigated using a four-component relativistic general open-shell configuration interaction method. All low-lying excited states below 3.0 eV are characterized by applying the f-shell Omega decomposition method, which was proposed by the present authors to analyze the electronic spectra of GdF. The ground states are ninefold degenerate and are expressed in the present terminology as X 4[(4f 7)(6s 1)]Ω. The superscript (4) here denotes the maximum Ω value. The electronic angular momentum projected onto the molecular axis (Ω) runs from 4 to −4, and the electronic configuration is represented symbolically by the gross atomic orbital populations of the Eu moiety (4f)7(6s)1. These features are consistent with the term X 9Σ that is assigned experimentally in the LS-coupling scheme. Similarly, the sevenfold degenerate first excited states are characterized as a 3[(4f 7)(6s 1)]Ω, corresponding to the experimentally assigned a 7Σ term. Dmitriev et al. observed three excited states Ω2, Ω1, and Ω3 above a 7Σ term. The three calculated excited states, A 4[(4f 7)1/2(6p 1)3/2 + …]2, A 4[(4f 7)−1/2(6p 1)3/2 + …]1, and B 4[(4f 7)5/2(6p 1+5d 1)1/2 + …]3, are, respectively, the most plausible identifications of the Ω2, Ω1, and Ω3 given by Dmitriev et al. These three states have large oscillator strengths with the X and a families.
    Theoretical Chemistry Accounts 01/2012; 131:1230. · 2.14 Impact Factor
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    ABSTRACT: The electronic structure of the LaO molecule is studied using frozen-core four-component multiconfigurational quasidegenerate perturbation theory. The ground state and nine experimentally observed excited states are examined. The ground state is (2)Sigma(1/2)(+) and its gross atomic orbital population is La(5p(5.76)6s(0.83)6p(0.14)p(*(0.21) )d(*(1.17) )f(*(0.26) )) O(2p(4.63)), where p*, d*, and f* are the polarization functions of La that form molecular spinors with O 2ps. We found that it is not necessary to consider the excitation from the O 2p electrons when analyzing the experimental spectra. This validates the foundation of the ligand field theory on diatomic molecules, including the La atom where only one electron is considered. The spectroscopic constants R(e), omega(e), and T(0) calculated for the ground state and low-lying excited states A'((2)Delta(3/2)), A'((2)Delta(5/2)) A((2)Pi(1/2)), and A((2)Pi(3/2)) are in good agreement with the experimental values.
    The Journal of Chemical Physics 03/2010; 132(12):124310. · 3.12 Impact Factor
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    ABSTRACT: The electron affinity of lead is calculated to be 0.403eV, using four-component relativistic multiconfigurational quasidegenerate perturbation theory. Uncontracted (27s 23p 16d 10f 2g) Gaussian-type functions are used to generate valence basis functions (7s 9p− 10p+ 8d± 10f± 2g±) in the reduced frozen core approximation, where the KLM shells are frozen. The electrons in the remaining shells are correlated in the perturbation calculations with the (6s, 6p) complete active space. The calculated value is within 10% of the experimental value of 0.364eV. The energy levels of the low-lying excited states of Pb and Pb− are also calculated.
    Chemical Physics Letters 06/2009; 470:158-161. · 2.15 Impact Factor
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    ABSTRACT: Multiconfigurational second-order quasidegenerate perturbation theory (MCQDPT) calculations were performed for the LaF+ molecule, with one LaF2+ and four LaF+ Dirac–Fock–Roothaan (DFR) spinor sets. The best spinor set was that of LaF2+, which gave the lowest total energies and also the best excitation energies for any state considered. The MCQDPT calculations with the cation and neutral molecular spinors were also performed for LaF. The MCQDPT with the cation spinors gave the lowest total energies for all states under consideration, and the calculated excitation energies compared best with experiment. We prefer the LaF+ spinor set to those of LaF. These calculations indicate that the DFR spinor set for the (n−1) electron system is adequate for treating the molecular electronic system having n electrons. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
    International Journal of Quantum Chemistry 12/2008; 109(9):1898 - 1904. · 1.17 Impact Factor
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    ABSTRACT: The electronic structure of the molecules LaF+ and LaF was studied using frozen-core four-component multiconfigurational quasidegenerate perturbation theory. To obtain proper excitation energies for LaF+, it was essential to include electronic correlations between the outermost valence electrons (4f, 5d, and 6s) and ionic core electrons composed of (4s, 4p, 4d, 5s, and 5p). The lowest-lying 16 excited states were examined for LaF+, and the lowest 30 states were examined for LaF. The excitation energies calculated for LaF+ agree with the available experimental values, as well as with values from ligand field theory. Errors are within 0.4 eV; for example, the highest observed state 2Pi is 3.77 eV above the ground state, and the present value is 4.09 eV. For LaF, agreement between the experimental and theoretical state assignments and between the experimental and calculated excitation energies was generally good, except for the electron configurations of certain states. Errors are within 0.4 eV except for a single anomaly; for example, the highest observed excited-state discussed in this work is 2.80 eV above the ground state, and the present value is 2.42 eV. We discuss the characteristics of the bonding in LaF+ and LaF.
    The Journal of Physical Chemistry A 04/2008; 112(12):2683-92. · 2.77 Impact Factor
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    ABSTRACT: We study the electronic structure of the ground state of the manganese dimer using the state-averaged complete active space self-consistent field method, followed by second-order quasidegenerate perturbation theory. Overall potential energy curves are calculated for the 1Sigmag+, 11Sigmau+, and 11Piu states, which are candidates for the ground state. Of these states, the 1Sigmag+ state has the lowest energy and we therefore identify it as the ground state. We find values of 3.29 A, 0.14 eV, and 53.46 cm(-1) for the bond length, dissociation energy, and vibrational frequency, in good agreement with the observed values of 3.4 A, 0.1 eV, and 68.1 cm(-1) in rare-gas matrices. These values show that the manganese dimer is a van der Waals molecule with antiferromagnetic coupling.
    The Journal of Chemical Physics 04/2006; 124(12):124302. · 3.12 Impact Factor
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    ABSTRACT: The experimental anomaly found in the interval between adjacent vibrational levels in the ionic C 1Σu+ state of the F2 molecule is analyzed. We have calculated the vibrational states of the first 1Σu+ state by numerically solving the one-dimensional Schrödinger equation using the Numerov method. The Rydberg state situated at the shallow local minimum in the first 1Σu+ potential curve possesses a single vibrational level, which is found to be smeared out in the ionic C vibrational states, resulting in this anomaly.
    Chemical Physics Letters 03/2005; 404(s 4–6):318–322. · 2.15 Impact Factor
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    ABSTRACT: The Si 3s23p1md11D2o Rydberg series is investigated. Experimentally, the series has a large constant quantum defect (QD) up to 3s23p16d1, which increases abruptly there after. Experimentalists consider that the increase in QD is brought about by a perturber 3s13p3. We show that 3s13p3 works as a strong perturber, giving a large and constant QD for the lower members of the series (m⩽6), but does not contribute to the abrupt observed increase in QD. It is found that 3s23p1md13F2o acts as a perturber for the higher member of the 1D2o series through spin–orbit interaction, giving a sharp increase of QD.
    Chemical Physics Letters 01/2005; 415(4):283-286. · 2.15 Impact Factor
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    ABSTRACT: By using multireference single excitation configuration interaction calculations and multireference single and double excitation CI calculations, we consider the 1Σu+, 1Πg, and 1Πu excited states of the F2 molecule which lie between 4.3 and 14.1 eV above the ground state. The basis set is composed of 13s, 10p, 7d, and 2 f contracted Gaussian-type functions, and covers molecular orbitals spanned by 4s, 4p, and 3d Rydberg orbitals. Of the 1Σu+ states, G 1Σu+ is sometimes disregarded, presumably because it is not directly observed by optical measurements, but is inferred from perturbations in the visible and ultraviolet spectra. We find that G 1Σu+ arises from the shallow local minimum in the lowest 1Σu+ potential curve, which also has a stable minimum corresponding to the state designated C 1Σu+. The experimental excitation energies (T0 values) for G 1Σu+ are 12.81–12.87 eV according to electron energy loss spectroscopy, and our theoretical value is 13.06 eV. Agreement between the experiment and the calculation is quite close. The state has a mixed ionic-Rydberg character with an interesting Rydberg portion. The experimental and calculated T0 values for C 1Σu+ are, respectively, 11.57 and 11.59 eV, suggesting that the present calculation for the state is reliable. Ambiguity found in experimental assignments of the vibrational levels for C 1Σu+ is settled here. The 1Πg and 1Πu states are also discussed. © 2003 American Institute of Physics.
    The Journal of Chemical Physics 03/2003; 118(12):5413-5421. · 3.12 Impact Factor
  • Hiroko Moriyama, Hiroshi Tatewaki
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    ABSTRACT: Gaussian-type basis sets for the 3d Rydberg orbitals and 3d correlation orbitals are developed for the first and second-row main group elements. The numbers of the Gaussian-type functions (GTFs) used for the 3d orbitals are 1-3 for the former elements and 1-4 for the latter elements. The 3d Rydberg orbitals for the firrst-row main group elements are close to the hydrogen (H) 3d orbitals, but those of the second-row main group elements are very different from H 3d except for Al. A two d or three d GTF set suffices to model the first-row main group elements, but at least four d GTFs are necessary for the second-row main group elements. The Rydberg GTF orbitals, consisting of three GTFs, are converted into correlating orbitals by introducing a single scaling factor. The correlation energies (CEs) calculated using these correlating orbitals cover 99.4-100% of those calculated using Dunning's three primitive GTFs for the first-row main group elements, and 94.9-99.7% of the CEs of Woon and Dunning's d's for the second-row main group elements. The resulting correlating 3d orbitals were tested by picking out F 2 and Cl 2 , yielding spectroscopic constants close to or more accurate than those calculated by Dunning's 3d orbitals and Woon and Dunning's 3d orbitals.
    Molecular Physics 01/2003; 101(1):53-63. · 1.67 Impact Factor