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  • 1
    Electronic Resource
    Electronic Resource
    An ab initio semirigid bender calculation of the rotation and trans-tunneling spectra of (HF)2 and (DF)2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5154-5159 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using a purely ab initio minimum energy path for the trans-tunneling motion in the HF dimer, the energy levels for the K-type rotation and trans-tunneling motion for (HF)2 and (DF)2 are calculated with a one-dimensional semirigid bender Hamiltonian and no adjustable parameters. The transition moments for rotation-tunneling transitions are calculated, using our ab initio value for the dipole moment of an isolated HF molecule, and we also calculate B¯ values. The energy levels we obtain are in close agreement with experiment; for example, the K=0 tunneling splitting in (HF)2 is calculated as 0.65 cm−1 compared to the experimental value of 0.658 69 cm−1. As well as showing that our ab initio minimum energy path is very good, the calculation demonstrates that the semirigid bender formalism is able to account quantitatively for the unusual K dependence of the rotational energies resulting from the quasilinear behavior, and that the trans-tunneling motion is separable from the other degrees of freedom. We use the results to predict the locations, and transition moments, of the ΔK=0 and ±1 subbands in the tunneling spectra of (HF)2 and (DF)2, many of which have not yet been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457613
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  • 2
    Electronic Resource
    Electronic Resource
    Variation with the intermolecular distance of properties dependent on the electron density in hydrogen bond dimers (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 11166-11184 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The variation with the intermolecular distance of features in hydrogen bond (HB) dimers dependent on the electron density ρ(r) are studied in four complexes representative of weak/medium HB interactions. Topological properties, energy densities and integrated atomic properties are obtained with ρ(r) of dimers at B3LYP/6-311++G(d,p) optimized structures obtained upon fully relaxing the geometry of monomers. The dependence of A–H(centered ellipsis)B bond properties on intermolecular R(H(centered ellipsis)B) distances allows to characterize the nature of the interaction as monomers move nearer from infinite separation. At long distances the interaction is only electrostatic while for separations about 1 Å larger than the equilibrium distance Req, quantum effects arising from ρ(r) begin to dominate. In the immediate neighborhood of Req the interaction is mainly led by the stabilization of the H-donor due in turn to energy lowerings in A and B atoms associated to polarization effects. The mutual penetration of electron densities of donor and acceptor monomers provokes a considerable reduction of atomic volumes for H and B atoms which reveals in the form of redistribution rather than transfer of charge. This range of distances exhibits noncovalent bond features but shortly after, when monomers approximate a few tenths of Å below Req, characteristics typical of covalent interactions begin to appear while the rate of change of all the ρ(r)-dependent properties increases rapidly. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1420749
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  • 3
    Electronic Resource
    Electronic Resource
    The conformational problem studied through the torsional Raman spectra of CH2DCH2D, CHD2CHD2, and CH2DCHD2 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1575-1590 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The torsional Raman spectra of CH2DCH2D, CHD2CHD2, and CH2DCHD2, recorded with an improved conventional Raman spectrometer, are interpreted here in the frame of an exact rotational–torsional Hamiltonian. The kinetic and potential operators of this Hamiltonian are discussed in detail, showing that the term responsible for the existence of two distinguishable conformers is of kinetic nature. For CH2DCH2D and CHD2CHD2 it is shown how to separate the rotational and the torsional motions by means of an appropriate choice of the molecular axis system. The wave numbers and intensities of both torsional Raman spectra are satisfactorily reproduced within the limits of the experiment with the following effective potential parameters: CH2DCH2D, V3=1002 cm−1, V6=6.0 cm−1; CHD2CHD2, V3=995 cm−1, V6=7.3 cm−1. For CH2DCHD2, only partially tractable in the present approach, an approximate estimate of V3=995 cm−1 has been obtained. Besides the quantitative interpretation of the torsional spectra, a discussion of the main facts of the conformational problem in connection to the spectroscopic observation is presented. In particular, the induced conformational transitions described here may contribute to the understanding of the elementary photoisomerization processes in molecules of the type AX2Y–AX2Y.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465326
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  • 4
    Electronic Resource
    Electronic Resource
    Optimized triple-zeta Gaussian basis sets for use with relativistic effective potentials (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 817-833 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contracted split valence 311 Gaussian basis sets optimized for the averaged relativistic effective potentials (AREP) of Christiansen et al. are developed for the main-group elements B—Ne, Al—Ar, and Ga—Kr. These triple-zeta basis sets are intended for use in valence-only molecular calculations with inclusion of correlation. The performance of the optimized basis functions is first analyzed in HF atomic calculations and compared with HF-limit results. Molecular calculations at the HF, MP2, and CISD levels of theory are performed for some selected diatomics, using these potentials and the optimized sets supplemented by one standard d-type polarization function. Results are reported for bond lenghts, harmonic vibrational frequencies, dipole moments, atomization energies, and ionization energies and compared with all-electron reference calculations and experimental data. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560490606
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  • 5
    Electronic Resource
    Electronic Resource
    Radial behavior of gradient expansion approximation to atomic Fukui function and shell structure of atoms (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 488-503 
    Details
    ISSN: 0192-8651
    Keywords: density functional theory ; electron density ; shell structure ; Fukui function ; atomic hardnesses ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An approximation to the Fukui function in atoms recently proposed in the form of a gradient correction to the local density approximation expression is here investigated. The spatial behavior of this function is analyzed, focusing on the gradient correction term. Physical information on the shell structure of atoms is shown to be conveyed by the radial distribution of that term. The analytically modeled densities (AMD) procedure is also implemented, and global atomic hardnesses are calculated with Hartree-Fock and AMD representations of atomic electron densities.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 488-503, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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