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  • 1
    Electronic Resource
    Electronic Resource
    Heteronuclear diatomic metal cluster ions in the gas phase: theoretical treatment of magnesium-iron cation (MgFe+) and study of its reactions with hydrocarbons (1991)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 113 (1991), S. 3274-3280 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00009a009
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  • 2
    Electronic Resource
    Electronic Resource
    On the dissociation energy of Mg2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5377-5383 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bonding in the X 1Σ+g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. Full configuration interaction (FCI) calculations are used to calibrate four-electron correlation treatments. We show that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, our best estimate of the dissociation energy (De) is 464 cm−1. We show that this is a lower limit and probably within 5 cm−1 of the complete basis value. The inclusion of core–valence correlation using a model operator approach decreases De by about 35 cm−1 and increases the bond length by 0.03 a0, thereby yielding spectroscopic constants in good agreement with experiment. Attempts to compute the core–valence effect accurately by expanding the CI treatment were unsuccessful.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458515
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study of metal noble-gas positive ions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4733-4737 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical calculations have been performed to determine the spectroscopic constants for the ground and selected low-lying electronic states of the transition-metal noble-gas ions VAr+, FeAr+, CoAr+, CuHe+, CuAr+, and CuKr+. Analogous calculations have been performed for the ground states of the alkali noble-gas ions LiAr+, LiKr+, NaAr+, and KAr+ and the alkaline-earth noble-gas ion MgAr+ to contrast the difference in binding energies between the simple and transition-metal noble-gas ions. The binding energies increase with increasing polarizability of the noble-gas ions, as expected for a charge-induced dipole bonding mechanism. We find that the spectroscopic constants of the X 1Σ+ states of the alkali noble-gas ions are well described at the self-consistent field level. In contrast, the binding energies of the transition-metal noble-gas ions are substantially increased by electron correlation. The difference arises from the contribution of metal-neutral noble-gas-ion character in the wave functions. This correlation effect increases as the ionization potential of the noble gas decreases from He to Kr and as the ionization potential of the metal atom increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456762
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  • 4
    Electronic Resource
    Electronic Resource
    Theoretical studies of the first- and second-row transition-metal methyls and their positive ions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2399-2411 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The metal–carbon bond dissociation energies (D0) and geometries for the first- and second-row transition-metal methyl neutrals and positive ions are determined. The computed D0 values for the positive ions compare favorably with experiment, except for RuCH+3, RhCH+3, and PdCH+3 where the experimental values are 10–15 kcal/mol larger. The computed D0 values for the hydride and methyl positive ions are similar for all metals in both transition rows except for Cu and Ag. However, for the neutral systems the D0 values for the methyls are smaller, especially on the right-hand side of both transition rows where the differences approach 15 kcal/mol. In general, the dissociation energies do not follow simple trends, as the individual D0 values are significantly affected by the relative spacings between the atomic states of the metal. The study of all of the methyl neutral and ions of both transition rows presented here provides a consistent set of data for the dissociation energies, thereby allowing a critical assessment of the experimental data for these molecular species, and an enhanced understanding of the different bonding mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456998
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of the structures and electron affinities of the dimers and trimers of the group IB metals (Cu, Ag, and Au) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2412-2419 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The molecular structure of both the neutral and negatively charged diatomic and triatomic systems containing the Cu, Ag, and Au metals are determined from ab initio calculations. For the neutral triatomic systems, the lowest energy structure is found to be triangular. The relative stability of the 2A1 and 2B2 structures can be predicted simply by knowing the constituent diatomic bond distances and atomic electron affinities (EAs). The lowest energy structure is linear for all of the negative ions. For anionic clusters containing Au, the Au atom(s) preferentially occupy the terminal position(s). The EAs of the heteronuclear systems can be predicted relatively accurately from a weighted average of the corresponding homonuclear systems. Although the theoretical EAs are systematically too small, accurate predictions for the EAs of the triatomics are obtained by uniformly scaling the ab initio results using the accurate experimental EA values available for the atoms and homonuclear diatomics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456999
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  • 6
    Electronic Resource
    Electronic Resource
    Near Hartree–Fock quality GTO basis sets for the first- and third-row atoms (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1043-1047 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Energy-optimized, near Hartree–Fock quality GTO basis sets are reported for the first-row (Li to Ne) and third-row (K to Kr) atoms. The most accurate basis sets reported for the first row are (18s13p) sets which are within 4 μEH of the numerical Hartree–Fock (NHF) results. For B to Ne basis sets with more than 15s functions are quadruple zeta in the valence space. For the first-row transition metal atoms the (20s12p9d) basis sets are triple zeta in the valence space and are approximately equivalent to Clementi and Roetti's accurate STO sets. Supplementing the (20s12p9d) basis sets optimized for the lowest state with the 4s23dn occupation with a diffuse d function gives SCF energy separations to the 4s13dn+1 and 3dn+2 states which are within 100 μEH of the NHF results. The most accurate basis sets for the transition metal atoms are within 30 μEH of the NHF results. In addition, energy optimized sets are reported for He(3P), Li(2P), and Be(3P).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456157
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: Theoretical study of the scandium and yttrium halides [J. Chem. Phys. 89, 396 (1988)] (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 7649-7649 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455759
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical study of the scandium and yttrium halides (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 396-407 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical spectroscopic constants are reported for the X 1Σ+ and a 3Δ states of the fluorides, chlorides, and bromides of scandium and yttrium. The calculated D0 values (eV) are ScF(6.00), ScC1(4.55), ScBr(3.90), YF(6.72), YC1(5.36), and YBr(4.74). All systems are predicted to have 1Σ+ ground states once the effect of unlinked higher excitations are incorporated using the coupled-pair functional approach and relativistic effects are included using either perturbation theory or relativistic effective core potentials. The singlet–triplet splitting is larger for the yttrium halides and decreases for both metals from F to Br. A complete-active space self-consistent-field plus multireference configuration-interaction study of the spectroscopic constants and radiative lifetimes is presented for most of the singlet and triplet states of ScF and YCl below 28 000 cm−1. The theoretical Te value computed for the B 1Π state of ScF indicates that the longest wavelength peak (9405 A(ring)) for the B 1Π←X 1Σ+ system observed in absorption in a neon matrix probably corresponds to the 2–0 band. The calculations provide an unambiguous assignment of two previously unassigned band systems in the laser excitation spectrum of the YCl molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455481
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical study of the A' 5Σ+g and C‘ 5Πu states of N2: Implications for the N2 afterglow (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3174-3186 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical spectroscopic constants are reported for the A' 5Σ+g and C‘ 5Πu states of N2 based on CASSCF/MRCI calculations employing large ANO Gaussian basis sets. Our calculated A' 5Σ+g potential differs qualitatively from previous calculations in that the inner well is significantly deeper (De ≈3450 cm−1). The potential also has a substantial barrier (≈500 cm−1) to dissociation with a maximum near 4.3 a0, and then a shallow (≈47 cm−1) van der Waals minimum near 6.3 a0. We suggest that it is the v=4 and v=5 levels that are involved in predissociating the a 1Πg and B 3Πg states, as opposed to v=0 and v=1 proposed by Verma. The deeper well in the A' 5Σ+g state provides considerable support for the theory of Berkowitz, Chupka, and Kistiakowsky who proposed that A' 5Σ+g is the primary precursor state involved in the yellow Lewis–Rayleigh afterglow of nitrogen. The theoretical De for the C‘ 5Πu state is also much larger than previous estimates. The previously unassigned Hermann infrared system (HIR) band positions correspond exceptionally well to our theoretical values for the C‘ 5Πu →A' 5Σ+g transition. This and other considerations lead to a rather convincing assignment of this transition as the HIR system. Einstein coefficients and radiative lifetimes are presented for this transition. Since the natural radiative lifetime of this state is much longer than experimental estimates, the C‘ 5Πu state may derive its actual lifetime through interaction with the C 3Πu state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453962
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical study of the alkali and alkaline–earth monosulfides (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6431-6437 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio calculations are used to determine accurate spectroscopic constants (re, ωe, De ) for the X 2Π and A 2Σ+ states of the alkali sulfides (LiS–RbS) and the X 1Σ+, a 3Π, and A 1Π states of the alkaline–earth sulfides (BeS–SrS). In contrast to the alkali oxides, all of the alkali sulfides have X 2Π ground states owing to the larger electrostatic interaction. For the X 1Σ+ states of the alkaline–earth sulfides, our recommended dissociation energies (D0 in eV) are BeS(3.27), MgS(2.32), CaS(3.29), and SrS(3.41), in overall good agreement with the (uncertain) experimental values. Our computed Te(a 3Π) and Te(A 1Π) values for BeS of 7269 and 8244 cm−1 are in excellent agreement with experiment. For the heavier alkaline–earth sulfides, our calculated Te(a 3Π) values (cm−1) are MgS(4218), CaS(6528), and SrS(6870), and our calculated Te(A 1Π) values are MgS(5068), CaS(6901), and SrS(7179). Core correlation increases the Te values for the a 3Π and A 1Π states of MgS, CaS, and SrS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454429
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